Nov 252015

Admit it. You (like me) have sat in front of the television watching pre-race interviews for a Camping World Truck Series race and asked yourself “Is that kid even old enough to drive?”

I thought maybe it was just me getting old, but the numbers bear me out. NASCAR drivers are getting younger. In the Sprint Cup Series, you have Eric Jones (19 and currently the youngest NASCAR main-series champion ever) and Chase Elliott (19). Kyle Larson, at 23, is in his second year as a full-time Cup driver.

All this age-related thinking was spurred, of course, by Jeff Gordon’s last race as a full-time NASCAR driver. Many of the tributes we saw last weekend credit Gordon with starting a “NASCAR Youth Movement”. He ran his first race at the age of 21 and won his first championship at 23, making him the youngest Cup champion in the modern era.

But is Gordon actually responsible for the “Youth Movement”? To answer that question, we go to the numbers.

TECHNICAL NOTE:  The official records appear to use a slightly different age convention. Example: Jeff Gordon was born on August 4, 1971. His first championship was in 1995.  As of August 1995, he was 24.

All the records say 23, so I’m assuming they use either the age at the start of the season or the age during the majority of the station or something. To make my life a little easier (so I only had to deal with years and not full dates), the ages I’m using are the current year minus the birth year. In other words, I’m using the biggest age the person was in that year.

Ages of Champions

Let’s start with how the overall ages of Champions have changed over time.


I know – it looks like random dots scattered over the page, doesn’t it? But here’s where what you should have learned in math and science class becomes useful. Look for trends. For example…


If we bound the data by showing how the extremes have changed over time, you notice that the bounding lines slope downward, toward younger ages with increasing time. In science, we call these “lines to guide the eye”, which is code for “I have no mathematical justification for drawing this line, but you see it, too, right?

See how two lines can make a trend stand out? But there’s a trend within a trend, too.

Look closely. There are groups of points that form lines going up and to the right. And they look like really, really straight lines. When something like that happens, you know there’s got to be a reason because points don’t line up like that by coincidence. If you look into the data, you’ll find it’s not coincidence at all.


Even Sprint Cup champions age. The straight lines represent drivers who have won multiple championships. Since they age one year every year just like us regular humans), their points form a consistent line with slope (rise over run) equal to one.

Notice something else, though.  Richard Petty won his last championship at age 42. The very next championship was won by an upstart 29-year-old (named Dale Earnhardt).

The trend repeats itself. When Earnhardt won what was to be his last championship at age 43, the very next year, the championship was won by a 24-year-old Jeff Gordon.

Aha! you say – the young buck comes in and unseats the veteran. So after Gordon won his last championship in 2001, he was unseated by… Tony Stewart, who was born the same year as Gordon and is, in fact, only two months and a couple of weeks younger than Gordon.

Continuing to buck the trend, the next “dynastical” champion (I made up that word, thank you.) was Jimmie Johnson — and he was older than Gordon was when Gordon won his last championship.

It’s true that Gordon started his run five years younger than Earnhardt, but if you look at the data going back to 1970, he’s merely continuing a trend, not starting it. And the trend didn’t even continue after him.

What About the Whole Field?

You can argue that the younger drivers are present, just not represented as Champions (yet). So I did the following: I took the top 30 drivers for seven years: 2015, 2010, 2005, 2000, 1995, 1990, 1985, and 1980. That’s the year Gordon won his first Championship, the four years after and the three years before.

I chose the top 30 drivers because (at least in later years) those are the drivers who tend to be full-time. They either run or attempt all 36 races. And since that’s the cutoff for The Chase, I thought it was fitting. I also chose the top 30 because I didn’t have time to look up birth years for all 125 drivers who ran at least one race in 1980. (The huge number of people who drove in 1980 actually becomes relevant later.)

Warning: The next graph is a little scary because it’s BIG. Bear with me. I’ll explain everything.

I made histograms for each year. A histogram tells you how many people were in a certain age range. Let’s start with the histogram for 2015, because it’s at the top. The information you should get out of this graph is that there were:

  • no drivers ages 16-20
  • 4 drivers ages 21-25
  • 4 drivers ages 26-30
  • 8 drivers aged 31-35
  • 9 drivers aged36-40
  • 4 drivers aged 41-45 and…
  • 1 driver aged 46-50 (Greg Biffle!)
  • no drivers 51-55.

Also that the perspective function in Excel graphs makes it hard to see the actual numbers. You’ll have to trust me.

Most of the histograms peak somewhere around 30-45. So much for the “youth movement”, huh? There may be the occasional young ‘un, but the vast majority of drivers are in the mid-range of ages. My calculation doesn’t include drivers like Chase Elliott, who will go full time next year and only ran a couple of races this year. But it also doesn’t include drivers like Michael Waltrip (on the other end of the age spectrum from Chase) who ran only the restrictor plate races this year.

Scroll down and see how the age ranges change over the years. You don’t actually have to think too hard because I’ll meet you at the bottom and explain.


Whew. Is there a trend to lower ages after Jeff Gordon appeared on the scene? Let’s see by comparing the average driver age over time.


The first thing to notice is that the average varies from a low of 33.1 to a high of 38.2, so we’re looking at a 5 year difference. So we do see the average age of competitors going down soon after Gordon entered the Sprint (then Winston) Cup. It looks like it’s starting up this year – but more on that in a moment.

One more look at this data, this time in the form of a high-average-low graph. The top green mark is the oldest driver, the blue box is the average and the red mark at the bottom is the youngest driver.  You clearly see that, to within a few years, there isn’t a big different between 1980 and 2010. In fact, we have older drivers running in 2010 than we had in 1980. And there was a 20-year old running in 1980 – Kyle Petty just like there was a 20-year-old (Joey Logano) running in 2010.


Overall, there is a decrease in average age since Jeff Gordon joined the series.  So there is definitely a correlation between Gordon entering the series and the average age of drivers shifting to lower numbers.


You knew there was a BUT, right? A correlation doesn’t necessarily mean there’s a causation. There are alternative explanations and factors that could also be responsible for the decrease.  To make a definite statement, we’d have to eliminate all those other possibilities. Which means we have to know what they are first. A couple thoughts.

  • The average age trend seems to be returning to higher ages in 2015. Did the Jeff Gordon Effect (JGE) wear off when he got older? Or maybe that’s just a fluctuation and it will continue down.  Or maybe, the large number of aging drivers taking up seats is preventing young drivers from joining up. These are all alternate theories and you can’t refute them (or the existence of the Jeff Gordon Effect) from the data here.
  • Look at the 2005 histogram – it’s different from the others. The other histograms show a nice peaky (“normal”) distribution, but in 2005, there were a lot of drivers in the 30-50 range. What happened to them? From 2005 to 2009, Rusty Wallace (48), Ricky Craven (40), Jimmy Spencer (48), Darrell Waltrip (53), Ricky Rudd (50), Dale Jarrett (51), Kyle Petty (48),  and Sterling Marlin (52) all retired. That’s a couple hundred cumulative years removed from the series. The drivers who replace these veterans are usually newer, younger drivers. So it’s possible you could have a decrease in average age without bringing in new, younger, drivers – just retiring out the older ones.
  • Finally, the nature of the Sprint Cup Series has changed profoundly.
    • In the old days, the team found the sponsorship and the driver. A new driver often has to bring his/her own sponsorship and companies are always looking for bright, smiling, young people to represent them well
    • The advent of the multi-car team changed a lot. All of a sudden, teams started having development programs, especially after 1982 when the XFINITY series started. You can’t deny that after Jeff Gordon was successful, a lot of owners started looking for young standouts.
    • What it takes to compete in terms of money and infrastructure has changed. Teams have to run a whole season to be competitive and there are far fewer drivers who drive one or a few races. Sorry. I just had to graph this.


Over the period from 1980 to 1995, there is a steep decline in the total number of drivers (blue squares). I also plotted how many drivers drove one race (orange diamonds) and how many drivers drove 5 or fewer races (blue triangles). It looks like most of the lost drivers come from those who were driving only a few races. Those drivers were often the older drivers. So this might be entirely responsible for the phenomenon we saw above, partially responsible, or just a correlation with no causation.

It’s a complicated question, so we resort to the statement all scientists use when they just don’t know: We need more data.

But it doesn’t really matter in the end if Gordon was responsible for the “Youth Movement”, right? Because Jeff Gordon has made such significant and lasting contributions to the sport, not just in terms of on-track, but also as a respected voice in the garage, especially in matters of safety. We were cheering for him Sunday, but as you all know…


Happy Thanksgiving Day to all my readers. I am thankful you’ve put up with me this long. I hope I’m becoming a better writing and just wish I could find more time to do it. Be safe on the road and in the kitchen. I’m also thankful to for being such a wonderful repository of data. I couldn’t do this kind of blog without them.








Nov 062015

The introduction of automotive safety innovations is usually accompanied by concern about the side-effects of those innovations. For example, when seat belts were introduced, people worried that the belts would keep them from getting out of a car quickly enough if they needed to. When HANS devices first became available, drivers also expressed worry that the protective devices would keep them from getting out of the car fast enough, especially if there were a fire.

On the race track, those worries were quickly put to rest when drivers wearing HANS devices were able to escape their cars just about as quickly as they could without the potentially life-saving devices on.

But there is another side-effect of safety innovations that has become known via a theory called risk compensation. This theory say that people typically adjust their behavior according to the perceived level of effect. For example, when it’s icy outside, people tend to walk more slowly and watch where they’re going more closely because the risk of falling is greater. When it rains or snows, you drive more slowly because you know it will take you more time to stop.

peltzmanThe opposite side of this effect is that when you make cars safer, people will drive more recklessly. This is embodied by the Peltzman Effect, which is named after University of Chicago Professor Sam Peltzman (shown at left). This gentleman’s research in business focuses on the interactions between the public sector (government) and the private economy. Professor Peltzman is a distinguished researcher, having served as senior staff economist for the President’s Council of Economic Advisors.

Peltzman was interested in whether mandatory seat belt laws actually had any impact on decreasing injuries or fatalities. Peltzman came to the conclusion that the increase in safety was essentially entirely offset by and increase in risky behavior by drivers (driving faster, not paying as much attention, etc.) Peltzman came to the conclusion that regulation was “at best useless, at worst, counterproductive”.

Not everyone buys Peltzman’s arguments.  There were a lot of technical criticisms about the data set he used and the particulars of the analysis. As I’ll mention in a moment, trying to get an appropriate data set for this is a lot trickier than you might think. You can find papers in the literature that both support and don’t support the Peltzman effect.

But the big sticking point is estimating the magnitude of the effect. I think about it this way:



When I make the car (or track, or personal protection equipment) safer, I decrease the probability that a driver is injured in an accident. But if my doing that increases the number of accidents in some way (for example, drivers try riskier passes, take more chances), then I could conceivably offset the improvements. Let’s consider three cases. I’ll make the same safety improvement each time, but we’ll look at how behavior changes vary.

CASE 1: The safety innovation prompts much riskier behavior and the number of accidents increases a lot. Even though you’re safer in the car, if there are more accidents, more people get injured. Think about everyone you know who thinks anti-lock brakes make them invincible in a snowstorm.

CASE 2: The safety innovation prompts riskier behavior, but the magnitude of the riskier behavior exactly offsets the safety innovation. There’s no change.

CASE 3: The safety innovation prompts riskier behavior, but not a large increase – so the net effect is that the number of injuries decreases, even though there is some riskier behavior happening as a result of the safety innovation.



As usual, I’ve oversimplified this terribly. It’s not that easy a thing to measure. Let’s say that I want to look at the effects of wearing seat belts in Charlotte and compare before  mandatory seat belt laws and after mandatory seat belt laws. There are records of accidents I can access and I can follow up on who was injured and how badly.

BUT… (there’s always a but)

  • What about weather?
  • What if people weren’t actually wearing their seat belts?
  • What if people were drunk when they had their accidents?
  • What about injuries in little sports cars vs. injuries in pick up trucks?
  • What about the world’s stupidest animal and accident causer – the deer?

We call these confounding variables and they make trying to get sense out of your data really difficult. The world is just not well-enough controlled for some analyses.

But you know what is?


Think about it. The cars are similar. Safety equipment is mandated. You’re not going to have to worry about Dale, Jr. unhooking his safety harness in the middle of a race because he needs to stretch. We don’t race when it’s wet (mostly). The drivers are of comparable quality (I know some of you would argue this, but if you look on the grand scale of all the drivers in the country, these guys are all in the top echelon compared to us.) And mostly, the animals stay off the track.

In a paper entitled “Automobile Safety Regulation and the Incentive to Drive Recklessly: Evidence from NASCAR” in the Souther Economic Journal, Russel S. Sobel and Todd M. Nesbit analyze publicly available NASCAR race and accident data from 1972-1993 with the goal of quantifying how much more riskier driver behavior has gotten as major advances in safety were implemented in NASCAR.

Racing is all about knowing when to take risks. If you’re going to chance wrecking your own car, that’s a high penalty for risky behavior. Injury is also a consequence. But if you know that you’re likely to walk away from an accident without injury, you’re going to be much more likely to take that risk that there’s just enough room for you to squeeze up into the next lane between two other cars.

I won’t go into the data analysis because there’s a lot of math things like differential equations and matrices and regressions. I will tell you that I learned a new fancy Latin phrase from reading this paper:  ceteris parabus, which means “all other things equal”. Sure, you can say ‘all other things equal’, but doesn’t it sound so much smarter in Latin?

Anyway, Sobel and Nesbit’s conclusion is that, for NASCAR drivers

“… a 10% improvement in NASCAR automobile safety results in approximately a 2% increase in reckless driving”

Then go on to point out that the increase in reckless driving isn’t enough to produce a larger number of injuries, but is large enough to prove that there is a negative driver response to safety innovations in the form of riskier driving.

They analyzed five drivers who drove from 1972 to 1998 (Yarborough, Parsons, Bobby Allison, Dave Marcis and Richard Petty) in an attempt to get away from some confounding variables, like people who only ran a few races. Even at this micro-level, they found that this group of drivers did get into more accidents as the car got safer, again confirming the authors’ earlier finding that safety innovations encourage risky behavior.

They point out something interesting, based on the idea that there are a group of race fans who want to see crashes, but don’t want to see people hurt. The riskier behavior produced by the safety improvements should actually help NASCAR attract those fans. More accidents, but fewer injuries.

This paper was from well before the Chase, but the current Chase format incentivizes drivers toward even riskier behavior. Even with higher speed and more at stake, remember that the last deaths in one of NASCAR’s top three series was in 2001.

And that got me thinking.

When they switched driving from the left side of the road to the right in Sweden in 1967, there was a drop in crashes and fatalities. For six weeks after the change, the number of car insurance claims were down by 40%. But after those six weeks, the insurance claims returned to normal. And after two years, the fatalities returned to where they had been.

I started wondering how many drivers on the track today were there at the Daytona 500 when Dale Earnhardt, Sr. died? Then I broadened that a little to look at who of that era was still active on track.

I took a pretty deep data dive and managed to confused myself a couple times, so let me explain exactly what I did.


The blue (taller) bars represent the total number of drivers who drove each season. If you look at 2006, you’ll see that out of the original 70 drivers who drove in 2001, only 36 of those drivers were still driving in 2006. The problem with that number is that it includes the road course ringers, the one-offs for people who only drive the Daytona 500, the retired drivers who do a few races a year and the like.

So I went ahead and looked at how many of those drivers were full time drivers – the ones who are the backbone of the series. That’s what the orange bars represent. In 2006, out of the 36 drivers who had been driving in the Series in 2001, 17 of those were driving full time in 2001.  You can also compare the full-time drivers from 2001 (24) with the 17 in 2006. That’s how many drivers who ran full time retired (or ran reduced schedules) between 2001 and 2006.

You can see a pretty clear and steady decrease (as you’d expect) as time goes on. In 2015, there were only fifteen drivers who had been driving (at all) in 2001 and are still around. Six of those were full-season drivers in 2001.

  • Dale Earnhardt, Jr.
  • Jeff Gordon
  • Matt Kenseth
  • Tony Stewart
  • Bobby Labonte
  • Michael Waltrip

Note that of the last two of these drivers, Waltrip has run 3 races and Bobby Labonte 4 races.

A couple other familiar full time in 2015 names and how many races they ran in 2001:

  • Kevin Harvick (35)
  • Kurt Busch (35)
  • Ryan Newman (7)
  • Jimmie Johnson (3)

So there are 8 current full time drivers in the Sprint Cup Garage today (out of 43+) who were racing in the era where drivers lost their lives on the track.  Out of those 8, only four (Stewart, Gordon, Kurt Busch and Dale Earnhardt, Jr. if I counted right) were on track when Dale Earnhardt, Sr. lost his life in the 2001 Daytona 500.

If I had a little more time, I’d go look at how the accidents for the next couple races compared to those from the year before in which there hadn’t been a fatal crash at the Daytona 500.

All this data is confusing, I know. So I thought about how to make it a little more accessible and came up with this interactive infographic! I looked at only the 43 drivers who competed in the most number of races each year in an attempt to get rid of the road course ringers and the one-offs. For each of the gauge charts, the blue bar tells you who ran full time in 2001 and ran most of the races in each year indicated. The yellow bar gives you the number of drivers running part-time in 2001.

There’s no orange bar in 2001, which is because the orange bar tells you how many drivers were not driving in the Sprint Cup Series in 2001.

What I’d like you to take away from this is that, as time goes on, the collective memory of the days when drivers lost their lives on a racetrack disappears. I’ve said over and over here, on the radio, everywhere, that there is no way to make racing 100% safe. Despite the best attempts of racing sanctioning bodies, there will be deaths on the racetrack. It’s a matter of the odds and the inherent danger of racing.

That’s why the current trend of ‘I’m mad at someone, I’ll crash him out’ is so disturbing. The probability of a freak accident is independent of intent. How many stories have you heard of people goofing off and something unexpected and tragic happens? It doesn’t matter it’s Martinsville and a slow track. Something in the car breaks and safety measures fail and we have a serious injury or maybe a death.

For my money, here’s the best commentary on the incident.

Tony DiZinno, who consistently provides smart, well-thought out and well-written commentary on motorsports of all types.

Ricky Craven is always on target. He’s got the driver’s perspective, he’s always measured in his thoughts and balances the practical with the ideal.

Nate Ryan and Bob Pockrass react to the Kenseth suspension. Two of the smartest guys on the NASCAR beat.


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Oct 162015

I finally got to the NASCAR Hall of Fame last week. It was a lot of fun, especially since I was there on a Monday morning and it wasn’t all that crowded. The next day they had the Chase drivers there for interviews, so I sort of lucked out having a lot of time to look at things without holding up anyone else.

I especially liked the exhibits that showed how much things have changed over time. Your first impression is to look at the lap belts and t-shirt/jeans that most drivers used back in the day and shake your head. But they didn’t know everything we know now about safety. You might think at this point we know everything we need to know about safety, but the field is constantly evolving.

Racing safety research presents unique challenges because the audience (the people who will benefit from it) is small — which means the money available is small.  I’ve talked about it before for catchfences. Count up how many tracks there are in the U.S. that have high-kinetic-energy motorsports (top level, Indy, NASCAR, F1) where cars launching into fences is possible. You might make a bit when you sell the first generation, but after that…? Maybe you can make some money off maintaining the fences, but they’re not something you replace frequently. It’s not a big market. So there’s a limit as to how much money a company can put into researching something that ultimately won’t make them a huge profit.

You might argue it’s different for driver personal protection equipment because you’re talking not only the few big-name drivers, but the slew of drivers in lower level professional and even the Saturday night racing circuit. Lower-level racers aren’t going to spend top-dollar for a safer helmet. The requirements at most small tracks in terms of safety are pretty minimal and if you give a driver a chance of putting money into making the car faster or making the car safer… You know what they’re going to do.


The head is one of the  most vulnerable parts of the body. The first function of a racing helmet was protecting against skull injuries. NASCAR was founded in 1947, just two years after the end of WWII. So it’s probably not surprising that many of the first racing helmets were actually repurposed military helmets. In the 1950’s, drivers switched from military to motorcycle helmets. (Take a look at the great photos at The Driver Suit Blog.) The purpose of these helmets was to form a protective shield around the head so that if you did bump your head, it wasn’t hard enough to crack it open. The National Geographic video below shows how motorcycle helmets are tested.

The helmets evolved to include a foam liner to cushion any blows. But even a well-padded open-face helmet (like the one on the left, below) leave plenty of room for injury. There’s no face protection. Many drivers wore goggles to keep dirt out of their eyes, but there was a compromise between safety and the ability of the driver to move and see what was around him or her.


Contrast the open-face helmet with the helmet on the right, which is a Bell HP7 carbon-fiber helmet that is favored by F1 drivers because it is light and aerodynamic (the latter being something closed-cockpit drivers don’t have to worry about.) It costs around $3,500. A good quality NASCAR certified helmet is around $700-$1,000, although drivers increasingly look to other series for anything that will provide an advantage.  Today’s helmets have electronics for communication, custom fitted padding around the face and inlets for cooling hoses.

NASCAR didn’t mandate closed-face helmets until after Dale Earnhardt’s passing in 2001. The argument was that the decrease in visibility could actually cause more accidents. But NASCAR quickly realized that accidents were going to happen, including the occasional ‘freak accident’ and their responsibility to the driver was to protect him or her in the worst-case accident.

Today’s helmets are remarkable and do an outstanding job of protecting drivers against blunt force trauma, cuts and such. But the more we learn about concussions and how seemingly insignificant impacts can have a very serious cumulative effect, the more we realized that helmets need to protect against not only skill injuries, but brain injuries as well.

I was at the University of Southern Mississippi earlier this week and learned that NASCAR drivers (as well as NFL players) may soon benefit from technology being developed for the U.S. Army. The military has the same problem as NASCAR (and the NFL), but on a much more serious scale. Fewer soldiers die on the battlefield, but more soldiers return from deployments with traumatic brain injuries. USM researchers have a $5M grant to study how to improve the military helmet to guard not only against blunt force injuries, but also against concussions.

Rawlings, a major manufacturer of helmets for professional and college football, are using one of their advances, which combines foam with pneumatic cushioning made of pressurized air bladders. This gives multiple levels of cushioning and protects both low-velocity and high-velocity impacts. Research geared at bringing home soldiers safely may also help NASCAR drivers extend their careers.


The first Strictly Stock race at Charlotte Speedway in 1949 didn’t require the racers to have roll bars or seat belts. That may sound nuts to the young people, but remember that many people didn’t use seat belts and it wasn’t even a requirement that car manufacturers put seat belts in their cars.

In fact, the first seat belt law was a Title 49 of the United States Code, which took effect on January 1, 1968 and required all vehicles to have seat belts installed.  Although the progressive state of Wisconsin required seat belts in the front passenger seat in 1961.

Seat belts save lives. There’s no debating that. Anyone who tells you that they survived an accident because they were thrown clear of the car is either totally wrong or extremely, extremely lucky. More people die needlessly in auto accidents because they aren’t wearing their seat belt.

I’m going on about this to toss in a gratuitous graph for Moody. Here’s the seat belt usage by state for 2013. Please note that I started the lower axis at 65% in order to make the differences more pronounced . I’m not surprised that Oregon is first. Oregonians like to be rebellious without being stupid. That’s a great state trait.

Safety_TwoandThreePointHarnessesIf you’re old like me, you remember when all we had in cars were lap belts. They’re called two-point harnesses because they are anchored to the car in two places. The three-point harness is now the passenger car standard and it’s called that because (duh) the belt attaches to the car in three places.

You’re beginning to see the trend, right?

OK, so if one is good and two are better… No, actually, the issue here is that the shoulder belt allows for rotational movement, especially if you’re hit on the side. So the next step is a four-point system, but the goal here is uniform retention of the body. Instead of a shoulder belt, you’ve got one belt for each shoulder.

Additionally, the place where the belts come together is now centralized on the body. It’s more easily accessible to the driver since it’s right up front. No need to twist or turn or fumble.


Here’s the problem with all three of these systems: Submarining. The video below (and this one) show you how, in some types of crashes, you can actually be pulled under the belt.  The reason they tell you to pull your airplane seat belt “low and tight across your lap” is because a poorly fitted seat belt is especially subject to submarining.


So someone came up with an idea and it’s a familiar idea for anyone who has ever had to put a young child in a car seat.

The 5-point restraint system.


I wanted to use the mounting instruction diagram from a race supplier to show you how specific they are about how the belts are mounted. That’s because of everything we’ve learned about safety, down to the angle at which the belts are installed making a difference in how well the driver is restrained.

They aren’t quite this precise when it comes to mounting baby seats.

The strap in the middle is called the anti-submarine (or anti-sub) belt. It’s there to keep you from sliding out under the lap and shoulder belts in a collision. But there was a bit of a problem with this configuration. Some drivers (predominantly those with the Y chromosomes) found this belt uncomfortable when tightened to the correct tension. Even worse, when there was an accident and the anti-sub belt did it’s job, the driver might find himself talking in a slightly higher octave for awhile.

So, no surprise here, right?

The Six-Point and Seven-Point Restraints


The anti-sub belt is replaced by two new belts, each of which secures one of the legs. This helps hold the driver in the seat and prevent anti-submarining. These are sometimes called “Negative-G belts”. The seven-point restraint is just the six-point with the anti-sub put back, so you have three lower belts: one around each leg and one down the middle. 2015 was the first year NASCAR required a seven-point restraint for all drivers. Since 2007, NASCAR had only required six-point harnesses.

Predictably, the move to seven prompted a lot of grumping about by the drivers, but there is a method to this. In most cases, the two leg straps will stop the driver before any tension gets into the third belt. But the third belt really helps keep the driver locked into the seat and becomes important when the car goes upside down. Austin Dillon credits the harness for allowing him to walk away from that horrible crash in Daytona last July.

So now you think you’ve got it down, right? You know what’s coming next.  The eight-point harness?

No. There is no eight-point harness.

Why a nine-point harness? The answer is in yet another piece of safety equipment: The HANS device. HANS is a head-and-neck restraint system that prevents the driver’s head from jerking forward and his neck snapping.


The HANS was designed to work with the existing restraint system, which at the time featured 2″ webbing in the shoulder belts. The shoulder belts go over the HANS device, holding it onto the driver’s shoulders. Remember – the driver has to be able to get out of the car in a really big hurry if necessary. There may not be time to undo or un-attach anything,  so the helmet and HANS device have to be of a size that it can fit through the window.

Here’s the issue. The wider a belt, the more it spreads the force out on the body. If you had a piece of wire and stopped, you’d be sliced in half. So the standard in NASCAR in the mid-2000s was three-inch belts everywhere; however, a 2-inch belt works really well on the lap and the legs. A 3-inch belt sits on your Iliac Crest (the bone that sticks out at the front of your hip.) If you use a 2″ belt, then the belt sits below the crest and transfer force to the pelvis, not the crest.

That means you can get a 2″ lap belt tighter than a 3″ lap belt because it just fits into the space better.

A 2-inch belt also works better with the HANS device — but, because of the geometry of your upper body, it’s a lot more comfortable to use a 3-inch belt and spread the force out over more of your chest.

Safety_Five-PointSchroth_2and3ShoulderStrapsThe first attempt to work this out was a belt that was 3″ where it went over the chest and 2″ where it went over the HANS device.  I’ve shown an example of this belt (in a 6-point restraint). See how the upper belts go from wider to narrower? That was the compromise. You can do this on four-, five- six- or seven-point restraint harnesses.

But more is better, right?

The Nine-Point Harness

The nine-point restraint system has two sets of shoulder belts. One of the sets (two belts) is 3 inches wide. Those belts sit under the HANS and against the drivers’ chest and shoulders. They are strictly to hold the driver into the seat.

The second set of belts are only 2 inches wide. They are the ones that go over the HANS device and hold it in place. So you’ve got separate protection for the driver’s and the HANS system that protects the driver’s neck and head.

I looked all over for a picture showing a nine-point harness and didn’t find one. I do know for sure that Logano uses one, and that many of the other drivers have switched to nine-point harnesses.  The 2016 rules package sticks with the 7-point harness as mandatory and recommends the 9-point harness. All systems must meet safety specification (SFI 16.6).  A set of belts costs about $1200 — and they must be replaced anytime the car is in an accident.

So to sum up harnesses:


Could you do an 8-point harness? You could. You’d leave off the anti-sub strap. But as far as I could tell, there’s no one making or marketing those.

So there’s your summary of where we stand on driver protection. Enjoy the races this weekend!

Oct 022015

Last week at New Hampshire, Kevin Harvick easily had the most dominant car, but failed to win the race. They ran out of fuel with three laps to go and finished 21st. The #4 team wasn’t the only team that gambled on gas, but they were probably the team that lost the most. Now they’re in a must-win situation this week at Dover.

Team owner Gene Haas said that the team made a “simple miscalculation” about how far they could go on the final tank of gas. As reported by Jared Turner on Haas said,

“Somewhere we were off in our calculations. That’s something we’ll be talking about tomorrow and the next couple days real hard.”

A lot of people wrote this week that Childers and Harvick have been their own worst enemies during this year’s Chase. Can a wrong calculation cost them a shot at a second title. Much Fuel Gets in the Car?

NASCAR race cars have approximately an 18-gallon fuel cell. Each fuel can (at right) holds about 12 gallons.

Before a pit stop, team members carefully weigh each fuel can and record the weight. After the pit stop, the fuel cans are weighed again.

The weight of fuel that went into the car is the difference between the two weights.

To get from weight to volume, you have to use the fuel’s density.


On their website, Sunoco gives the density of the E-15 fuel that NASCAR specifies for all cars and all races as 6.2 lbs per gallon. That’s accurate enough that we can suss out that the weight of the fuel inside a 12-gallon fuel can is (12 gallons x 6.2 lbs per gallon =) 74.4 lbs.  The fuel plus can weighs about 94 lbs total, which is why the gas man is usually right up there with the jackman in terms of pit crew member muscles. It takes about 10 seconds to fully empty a can of fuel into the car.

So let’s say that we put 105 pounds of fuel in the car on the last pitstop. Then we can back calculate how many gallons that is:


This seems like a pretty coarse calculation, but Sunoco actually provides a much more specific value for the density to the teams each day. Why would it change? Temperature and humidity can affect the density of any gasoline – which we talked about the last time we were in Dover when Kurt Busch’s team was told they weren’t allowed to try to cool down the fuel during an unseasonably hot race.

This is how regular gasoline changes density as a function of temperature. When the temperature rises, the molecules in the gasoline like to have slightly more space between them, which means that there are fewer molecules in a given volume. If you had a row of seats that normally sat six and you insisted on having an empty seat on either side of a person, you’d end up with only three people in the row instead of six.


The E15 fuel that NASCAR uses has a similar change in density with temperature. Humidity can also impact the density because ethanol likes to absorb water. So each morning, Sunoco distributes a very precise (measured) number to the teams and that is the number they use. It’s an incredibly precise (and simple) calculation to make.

Theoretically, you’d have to make a pretty massive mistake to screw up that number.

But the big uncertainty in fuel mileage calculation is not in the calculation – it’s in the assumptions that go into the calculation.  There’s really two levels of assumptions, too:

  1. How much fuel got into the car and
  2. How fast is it being used?

And, as the diagram below shows… there are a lot of places to screw things up.

Gas In

Spillage and Leakage: We used to have an outlet on the gas tank so that any overflow would go into a catch can. That amount was put back into the gas can and weighed. The new models of gas cans are supposed to prevent spilling, but if you don’t get the can coupled to the gas inlet correctly, or if there’s a malfunction with the gas can, you can spill gasoline on the ground or on yourself. That’s gas that doesn’t get accounted for when the cans are weighed. And since everything happens quickly, it’s possible no one can tell how much was spilled well enough to make a good estimate. It’s also possible that there’s a leak in the fuel line or the fuel cell, although that’s a rather more serious issue because that goes to safety.

Miscalculation: It is surprisingly easy to screw up a calculation when you’re in the rush and crazyness of a race weekend, especially if you’re short-handed, new or a lot of things are changing – or even if you have a new baby and you’re not sleeping much. Someone reads the scale wrong and reports the wrong weight. Someone messes up the excel spreadsheet where the calculation is done, or you’re using the wrong density for some reason. These are the most irritating possibilities because, frankly, they are preventable.

Hold that last thought because I’m coming back to it later.

Gas Out

Here’s where things get really tricky. You’ll hear commentators throw about a number like 4.6 miles per gallon under green and half that under caution. In reality, the teams try to make much better estimates of these two numbers because they are absolutely critical.

Measuring Gas Mileage: Most drivers don’t get the same mileage at all tracks. Gasoline usage is tracked carefully during practices. Gas mileage changes with the condition of your tires, so every time the tires are changed, the gas mileage calculation is done anew. Over the course of a couple hours of practice, the crew chief gets a snapshot of how his or her particular driver’s style at that track with that particular set up uses fuel.

But when you’re racing, some of that goes out of your hands. If there’s someone on your tail and you don’t want to give up a position, the driver may be more aggressive, which means he or she is using gas at a faster rate.  The teams get scads (a techincal term) of data from the Electronic Fuel Injection system that they can mine for more information about how their driver and car use fuel at different tracks.

Cautions: Is it me, or has there been a lot more talk in recent years about drivers’ abilities to save fuel under caution? They’ve always played games like flipping off the ignition and coasting during cautions, or driving on the apron to decrease the distance traveled. Now we’re hearing more about getting off the gas a little earlier, getting on a little later. I think a lot of that focus on finesse is due to the EFI date. After a race, you can go back and show your driver how good he or she was at saving gas.

So What Happened to Harvick?

You have to understand that, for an engineer, being accused of screwing up a calculation is like being stabbed through the heart. It’s a simple calculation and you’d have to be pretty far off your game to screw it up.

So I wasn’t all that surprised when Rodney Childers tweeted an explanation of what went wrong and used some choice words in reference to the people calling for his head for costing Harvick a chance at winning the race.

BSPEED_2015_NHMS_ChildersFuelMileageRaceChilders was able to look at the EFI (Electronic Fuel Injection) data and determine that Kevin had saved enough fuel that they should have had six laps worth of fuel left. They should have been able to finish the race with fuel to spare.

But they were short by three laps.

This can only mean that they overestimated the amount of fuel that went into the car.  Childers suggested the crew hadn’t gotten all the gas from the can into the car or that possibly a fuel cell bladder might have “come apart”. It’s also possible someone misread the scale or mis-recorded the weight.

As he points out, these kinds of mistakes are pretty rare (and I add, especially with top-level people like Childers and his crew) – but it couldn’t have come at a worse time.

Ultimately the crew chief takes responsible for everything except driver decisions, so it does fall on Childers’ shoulders – but all the commentaries attacking him for using bad judgement at New Hampshire are just wrong. He made the right decision based on the data he had in front of him. That data was incorrect. The problem isn’t the judgement – it’s the data.

And you can bet they are going over every step of every process this week at the shop because Dover is their last chance to keep their hopes alive for a repeat championship.

Fuel mileage concerns never go away. Just for kicks, I wanted to see how much fuel you needed for each of the tracks in The Chase.


Remember that there are 128 ounces of fuel in a gallon, so even at the longest track in the Chase, you’re talking about a little more than a half-gallon of fuel for that last lap. If you think about the times someone’s run out of fuel coming around turn 4, divide those numbers by four and in some cases (looking at you, Martinsville), as little as a quarter of a cup of fuel could lose you a race. This is a sport not only of tenths and hundredths of seconds, but also of quarter and half-cups of fuel.

Disclaimer: Back in 2008, Rodney Childers was one of the crew chiefs for Elliott Sadler and I spent a weekend with the team at Daytona while writing the update for the paperback version of my book. His desire to win coupled with a measured calm and can-do attitude makes him a person you really can’t help but like and admire. So I’m probably biased toward him, but I think my analysis still holds up!

Sep 182015

Every year about this time, someone grumbles that The Chase needs a road course. The frequently-cited rationale is that the regular NASCAR season has two, so a champion should prove he or she can perform on the same racetracks that make up the regular season.

This seemed like one of those things you can solve with data. Is the Chase really reflective of the overall NASCAR season? Let’s start by classifying the tracks. I broke them down as follows:

Track Type Tracks Included
Short Tracks (less than a mile) Bristol, Martinsville, Richmond
1 to less than 1.5 miles Darlington, Dover, New Hampshire, Phoenix,
Intermediate (1.5 mile) Chicago, Kentucky, Atlanta, Texas, Charlotte, Homestead
2-2.5 mile Indy, Pocono, Michigan, California
Superspeedways Daytona, Talladega
Road courses Watkins Glen, Sonoma

Then I went through and counted.


Because I have counting issues.

Track Type Regular Season Chase Total
Short Tracks (less than a mile) 4 15.4 2 20.0 6 16.7%
1 to less than 1.5 miles 5 19.2 2 20.0 72 19.4%
Intermediate (1.5 mile) 6 23.1 5 50.0 11 30.6%
2-2.5 mile 6 23.1 0 0 6 16.7%
Superspeedways 3 11.6 1 10.0 4 11.1%
Road courses 2 7.7 0 0 2 5.6%

I know we usually break things into small, intermediate and big, but let’s take a little more detailed look, okay?

Of course, it’s not science without colorful graphs, right? Let’s start by looking at the distribution of races throughout the whole season. As you can see from the pie chart….


… a NASCAR season is pretty well balanced. You’ve got a little more 1.5 mile tracks, but there are more 1.5 mile tracks out of the tracks NASCAR runs than anything else, so that makes sense in terms of supply and demand. Now let’s compare that to the regular (first 26) and chase (last 10) races.



So I thought this was pretty interesting. We knew that 1.5 mile tracks make up half the chase, but in addition to there being no road courses, there are also no 2-2.5 mile tracks. There are about the same proportion of superspeedways, short and 1-1.5 mile tracks, but the places that would have been taken by a road course and a 2-2.5 mile track is replaced by 1.5 mile track.

The husband said that trying to compare pie charts was too confusing, so I also put this together in terms of a bar chart. The legend turned out a little small, so I’ll note that the light green is the regular season, the blue is the chase and the purple is overall (a weighted average, since there are 26 races in the regular season and only 10 in the chase.)



Let’s Fix This!

Okay, let’s go on the assumption that The Chase, in order to crown a real champion, should reflect the regular season. What do you change out?

Here’s the problem. The Chase happens in September, October and November. Where are all the 2-2.5 mile tracks? In the Northeast or Midwest. Pocono in November would take a huge chance in terms of weather. There’s California and you could pair that up with Phoenix to make a mini West-coast trip. Given that the racing’s been so much better there lately, that might be an option. But I’ll tell you, come the last couple races of the season, everyone is exhausted. The logistics of getting two cars out to the west coast are complicated and everyone is just bushed.

There’s the same problem with the road courses. Watkin’s Glen in the fall is iffy and Sonoma brings up the whole West Coast argument again.   Road Atlanta would work… but then we into the question of taking a race away from another track.


I got curious about the geographic distribution of races, so I tallied that up as well. Not surprisingly, the majority of the races are run in the Southeast, as befits a sport that originated in the Southeast. I did do the pie charts for Regular Season vs. Chase – but the distribution really doesn’t change, so I decided not to include those. (It takes time to make these things!)




I also looked at the distribution of the Nationwide series compared to the Sprint Cup Series. Since they run together at a lot of tracks, I expected it to be pretty close. It was.


Sep 042015

I get this question a lot: If NASCAR decreases horsepower for everyone, how does that make it easier to pass? You’re basically taking everyone down by the same amount, right?

To explain this, we have to touch on a couple concepts.  Moody asked me this a couple weeks ago and I gave him a really crappy answer. I’ve been feeling guilty ever since.

Horsepower vs. Torque

We usually talk about horsepower when we talk about engines, but the important quantity here is actually torque. As a friend likes to say, horsepower lets you go fast, but torque makes you feel good.

Horsepower is how fast the engine delivers energy. (Power is energy divided by time.) Horsepower is actually a unit. It was proposed by James Watt (the 18th Century Scottish inventor, not the Secretary of the Interior under President Reagan). The Scottish Watt invented a viable steam engine by understanding some very complicated thermodynamics, most of which wouldn’t be formalized by scientists for another 100 years. His Watt Steam Engine was a critical driver of the Industrial Revolution.

Watt was successful at convincing a lot of people who ran factories to switch from the current Newcomen steam engine, which was extremely inefficient and used a lot of coal to make a little bit of power. Watt’s engine needed much less coal and he actually licensed the engine to people for royalties – he got 1/3 of the money they saved on coal relative to the Newcomen engine they had been using.

But there are only so many industries. Watt saw his engine as being useful to much smaller enterprises, like mills. But this was a different PR task. You weren’t convincing people to trade out one machine for another – you were convincing them to trade out their trusty horses — which work steadily and require only a little hay and water — for a machine.  It’s a real paradigm shift. How do you even compare two things that are so dissimilar?

Watt estimated – and I use the word ‘estimated’ loosely – the power of an average horse. He sort of measured it on what I’d describe as a horse dyno. That gave him a way to parameterize the power of his steam engine in terms of what he hoped to replace: the horse.

Nowadays, most of the world uses the metric unit for power – the Watt. One horsepower is 746 Watts. So that 60-Watt lightbulb in your lamp is actually a 0.08 horsepower lightbulb. A 1000-W hairdryer is about 1.3 hp. A 750-hp engine is the equivalent of 932 60-W lightbulbs.

Object Power
hp Watt
60-W lightbulb 0.08 60
100-W lightbulb 0.13 100
hairdryer 1.3 1000
lawnmower 5.0 3,730
2016 Ford Mustang V-6 300 22,380
race engine 750 55,950

Torque vs. Horsepower

Torque and horsepower are both properties of an engine. As we’ve discussed before, we usually talk about peak values (like the Mustang engine above is 300 hp at 6500 rpm), but the actual values depend on the engine speed (in rpm). A friend who designs engines likes to tell me…

Horsepower lets you go fast. Torque makes you feel good

Power is how fast you can supply energy – and determines your ultimate speed. But when you step on the gas, what you really want is acceleration.

A minivan and a Mustang both reach 60 mph. But there’s a big difference between punching the gas and hitting 60 mph at the end of the on-ramp and standing on the gas and it taking fifteen seconds to get to 60 mph. Speed is good, but acceleration is actually much more important. And acceleration requires torque.

Torque and horsepower are related, as shown in the graph below.


Every torque and hp curve you see will have the torque and the horsepower curves cross at the engine speed of 5252 rpm. That’s because the horsepower and the torque are related to each other by a pretty simple equation.



So when NASCAR limited horsepower, they also effectively limited torque. That, in turn, limits how much acceleration you get.

Kinematics and Quadratics

This is a perfect time of year to discuss this because every high school student starting a physics class is probably learning about distance, velocity and acceleration right now.

Velocity is how much distance you travel in a particular amount of time. If you’re going 60 mph, it literally means that you go 60 miles every hour.

Acceleration is how fast you change your speed. A Bugatti Veyron goes from 0 to 60 mph in 2.4 seconds, which means that it goes (on average) 25 mph more every second,.

When you’re coming out of turn 2 or turn 4, onto the straightaway, what you want is acceleration. You’ve had to slow down to take the corner, so the goal is to be going as fast as possible coming out of the turn, accelerate as quickly as possible, and put as much distance between you and the guy behind you as possible.

No Acceleration

The distance you travel at a constant speed is proportional to the time.  If you go 60 mph, after one hour, you’ve gone 60 miles. After two hours, you’ve gone 120 miles. After three hours, you’ve gone 180 miles. It’s linear.

This seems obvious, but if I am behind you by half a second, there’s no way I can pass you unless I go faster. But just look at how much faster I have to be going.


Car 1 is the blue line, going at 180 mph. Assume car 2 is a half second behind. If car 2 goes 190 mph, then it will take just about 9 seconds for car 2 to pass car 1and that’s the red line.

If Car 2 goes 200 mph, it takes only about 3 seconds for car 2 to pass car 1.

Of course, if we’re talking about cars directly battling for position, we’re probably talking about one being a tenth of a second behind. In that case, if car 1 goes 180 mph, car 2 going 182 mph would take almost six seconds to pass and car 2 going 184 mph would take about 2 seconds.

The Magic of Quadratic Dependence

Here’s the big deal for acceleration. The distance you travel is proportional to the SQUARE of the time.

Let’s do this first with simple math. Let’s say you accelerate such that you travel 100 feet in one second. After two second, you haven’t gone 200 feet – you’ve gone 400 feet. And the longer you go, the bigger the difference gets.

Time  Distance
Linear Quadratic
1 100 100
2 200 400
3 300 900
4 400 1600
5 500 2500
6 600 3600

I think graphs are easier to see this, so here’s a representative graph. Both cars have the same acceleration; however, Car 2 doesn’t start accelerating until half a second AFTER Car 1.

BSPEED_KinematicsofPassing3The interesting thing here is that the distance between the two cars doesn’t stay the same. Car 1 gets further and further ahead just because how far it goes depends on the square of the time. Car 2 never catches Car 1.

Another words, the long Car 1 accelerates, the more distance it puts between it and the car behind it.

What if Car 2 can accelerate faster?


After some time, Car 2 will pass Car 1. How long that takes depends on both car’s accelerations.

But there’s one more important thing we have to consider.  How long the cars accelerate.

Terminal Speed

An engine can’t accelerate indefinitely. At some point, it reaches its top (or terminal) speed. Then the distance it travels goes back to depending linearly on time. The graph below shows a car that accelerates for four seconds, then reaches its terminal speed. Notice how the graph changes from being quadratic to being linear at the crossover?



Compare that graph with how far the car would’ve gone if it kept accelerating. I’ve shown the quadratic in blue below and the same behavior as in the graph above in red. You can see how much further the accelerating car goes and that distance just keeps growing bigger the longer you go out in time.


When you reduce engine power, you have a lower terminal speed and you reach it faster. That means you don’t get to put as much distance between you and the next guy. And that was the big complaint in a lot of places. One guy gets out front coming out of turn 2 or 4, gets a big lead coming down the straightaway, and the guys behind don’t have a chance of catching him.

At the big places like Indy and Michigan, that was one of the big problems. A car got going down the straightaway and it was gone. There was no catching up to it. The theory behind the lower horsepower there is that the cars reach terminal speed faster, which limits how much of a lead a car can get. The same idea applies pretty much anywhere.

So why doesn’t NASCAR just do the calculation and figure out the sweet spot for each track? Too many variables. A driver will get on the gas at a different point coming out of a turn, or brake later going in. There’s no way to precisely figure it out.

But the general principle applies. If you limit acceleration and top speed for everyone, you limit how much of a lead a car can get. That means that the cars behind have a chance at passing for the lead.


Aug 212015

A lot of drivers cite Bristol as one of their favorite tracks. It’s a great exhibit for the argument that racing is more than just pure speed. High banks (which we know mean speed!) and a short track, which means tight racing. But a lot of drivers will tell you that Bristol is one of the most exhausting, physically demanding tracks on the circuit. Add to that the inherent stress of short-track racing, where 43 cars are operating in a limited (half-mile) track.

Regular readers know that the force it takes to turn a race car is given by:


So it is harder to turn (i.e. you need more force)

  • when you have a heavy car
  • when you’re going fast
  • when you’re trying to make a tight turn

So when you compare a thousand foot turn radius like at a superspeedway with the 250-foot turn radius of Bristol, it’s four times easier to turn at Daytona  — if you’re turning at the same speed.

Turning Force

Using a typical weight for a Gen-6 car (3300 lbs of car and 180 lbs of driver), we can figure out how much force it takes to make a car turn.  (Disclaimer: Parts of this table are from a previous blog.)

Track Turn radius
Turning Force
Talladega 1000 33 180 6,848 1.97
200 8,456 2.43
Daytona 1000 31 180 7,532 2.16
Bristol 242 24-28 130 16,235 4.67
100 9,606 2.76

Newton’s First Law says that a car going straight down the frontstretch at Bristol will keep going straight (and into the wall) unless a force acts on it and causes it to turn.

Consider a soccer ball rolling past you. You want to change its direction, so you kick it at a right angle to the direction it’s headed. The faster it’s moving, the harder you have to kick it to change its direction. The direction it goes is a combination (a physicist would say “a vector sum”) of the direction it had been heading and the direction of the force (the kick) you applied to it.

Putting Turning Force in Perspective…

Just to put these numbers in perspective, let’s look at one of the largest land animals, the elephant. My father always made a big deal of knowing the difference between an African and an Asian elephant. The African elephant is larger (up to 13 feet tall) than the Asian (“only” 12 feet). You tell them apart because the African elephant has much larger ears, has two ‘fingers’ on its trunk, and has much more wrinkly skin. The Asian elephant has smaller ears, only one ‘finger’ on its trunk, and smoother skin on the head and face.


What does this have to do with anything? An adult male African Elephant weighs, on average, 15,400 pounds.

Turning a NASCAR race car at Bristol at 130 mph requires a force slightly greater than the weight of an African Elephant.

I’ve graphed the force needed to turn as a function of speed below. (Note that the turn radii at Bristol are different for turns 1/2 and 3/4. Turns 1/2 have a turn radius of 242 ft, while 3/4 have a turn radius of 256 ft.)



Compare this to Daytona, which has higher speeds, but also larger turns.


So it’s actually easier to turn at Daytona, even though the speeds are a higher, you’ve got four times more turn radius.


We can also look at this in terms of the g’s the drivers pull while traveling around Bristol.


Just for reference, most amusement park rides top out at about 3G; however, some roller coasters go up to 4G (SheiKra Rollercoaster at Tampa) or 4.5G (e.g. the Titan Rollercoaster in Texas).

Although the “G” is the acceleration due to the Earth’s gravity (which always points to the center of the Earth), we use G to measure acceleration in any direction: up or down, back or forth, or sideways.  Drag racers experience accelerations of about 5G backward at take off.  When you’re turning at constant speed, the acceleration is sideways (which engineers call ‘lateral’).

The green line is on there because around 5-6 G’s, drivers start to be impaired because the forces actually change the ability of the blood to circulate through the body. Drivers may experience greyout, which is a loss of color vision, tunnel vision (loss of peripheral vision), blackout (complete loss of vision, but still conscious) and finally G-LOC (which is loss of consciousness because of gravitational forces) .

Now, if you’re paying close attention, you will notice that the graph of ‘G’s and the graph of forces look very similar. In fact, they are the same trend because you get the g’s by dividing the turning force by the mass of the car and the acceleration due to gravity (32.2 ft/sec/sec).

The Effect of Banking: Inside Line or Outside Line

One of the most interesting things about Bristol is that it now has graduated banking – from 24 degrees to 28 degrees. As we’ve discussed before, the higher the banking, the more the track helps the car turn. But here’s the twist: If you go up high to take advantage of the higher banking, you actually have to travel a longer distance.  The racing surface width is 40 feet. Now, one of the problems with the way track measurements are specified is that you don’t actually know where they measured the track length.

BSPEED_Bristol_TrackConfigLet’s assume for the purposes of argument that the 0.533 width was measured at the apron – which means that the end of the track at the outside wall is 40 feet further out. The distance down the front and back stretches are the same, so all we’re worried about is the difference in the turns.

If you take the outside line rather than the inside line, you’re going about 125 feet more distance than your competitor who takes the inside line. So you have to find out, given your car’s setup, whether the additional banking helps you turn faster.

If you take the outer line then at 130 mph, you need 13,910 lbs of force, compared to the 16, 235 lbs you need at the inside. You pull 4.00 gs instead of 4.67 gs on the inside. At 130 mph, you’re covering 190 feet per second, so the time it takes you to traverse the extra 125 feet is a little more than half a second. Not much, right?

Except lap times run around 15 seconds.

At the April race, final practice times ranged from 15.043 seconds (Kurt Busch, in first place) to 15.818 seconds (Alex Kennedy in 43rd place).  Half a second takes you from first to 40th place. So you darned well better be faster if you’re traversing the outside.

Now, I don’t know where the 242.45 feet for the turn 1/2 radius was measured. If it was measured at the midpoint of the track, then the differential is smaller, but I figure I’d take the most extreme case to make the point.

Related Posts:

Racing Without Friction

Why Turning is Hard

Aug 072015

Analog vs. Digital

VinylRecordAlbumThe big difference between analog and digital is continuous vs. discrete. An analog signal is a continuous signal in which something like a pointer moves the same way as something else. For example, an analog multimeter has a dial that moves in proportion to the voltage it is measuring.

Those of you of a certain age may remember these odd looking flat black vinyl things called ‘records’. Records are analog devices. A groove is cut into the vinyl. A stylus rides along the groove and translates the wiggles in the groove into an electrical signal, which is then transmitted to a speaker, which turns it into a vibration (which, when pleasant, we call “music”.)

Digital files (your mp3s, for example; everything on your iPod) encode music in 0s and 1s. Instead of a continuous, physical groove, it’s a bunch of data. There are a lot of advantages to digital. It doesn’t degrade with repeated playings, it’s much less fragile, and you can include a lot more information compared to a record player.

On the other hand, digital music can loose some of the ‘character’ of analog music and you cannot substitute a mp3 file for a frisbee.

Like music, the gauges on a car may also be analog or digital. Up until now, NASCAR hasn’t allowed digital gauges. Here’s examples of all three:


On the left is an analog gauge. This is the usual dial gauge that many cars still have. Like the record and the needle, physical components move in response to the car’s speed. (How Stuff Works has a nice explanation of how speedometers work.)

In the middle is an analog gauge that’s been supplemented with LED lights. This was the big deal change a few years ago. The driver didn’t have to squint and try to read the divisions of the gauge. The mechanics would pre-set the gauge so that a few lights would display when the car reaches a particular rpm. The really fancy gauges even had different colored LEDs so that the driver not only had the lights turning on, but the colors to warn them.

A Brief Digression about LEDs

The LED-modified gauge didn’t work its way into racing until the last five to seven years. There’s a good reason why. LEDs are a pretty new innovation. Yes, now you can buy LED lights that change colors and change their colors using your phone.

The principle behind Light Emitting Diodes (LEDs) was discovered in the 1920s, but the first practical LEDs didn’t show up until the 1960s. The first LEDs (circa 1962) were red and so low brightness they were difficult to see. Remember the first calculators?


They had to add plastic, prismatic lenses to make them easier to read because they were hard to read by themselves. They just weren’t bright enough. It wasn’t until the 1970s that high-brightness, affordable LEDs were being made and the spectrum of colors ranged from red to… orange-yellow.

As you move through the rainbow, the wavelength of the light changes. Red is somewhere around 700 nanometers and violet around 400 nanometers. We figured out how to make longer-wavelength LEDs first from a semiconductor material called Gallium Arsenide Phosphide. High-brightness blue LEDs were not invented until 1994 and utilized a different semiconductor called Indium Gallium Nitride. This led to the development of white-light LEDs (you use phosphors to convert blue to red. yellow and green). White light is the combination of all colors and that’s why you can now go and buy a LED lightbulb. The reason we didn’t have LED gauges until recently is that the LEDs needed to be bright and robust enough to survive being a racecar. But those gauges are about to become history. NASCAR will allow digital gauges.

Back to the Digital Tachometer

A digital tachometer gives you numbers directly.  No more trying to read the tiny little divisions on an analog gauge to see how close you can get to your pit road cut off without going over. Whereas an analog tach may tell you you’re somewhere between 4000 rpm and 4100 rpm, the digital tach will tell you you’re at 4036 rpm. Most of the time, that type of precision isn’t good for anything — but when you’re on pit road and trying to stick below the pit road speed limit, you want to know EXACTLY how fast the engine is going.

Actually, you want to know how fast the car is going. Any gauge can be digital – oil pressure, speed, fuel pressure… pretty much any gauge can be made digital.

A digital gauge MAY include a graphical display of some type – sometimes, even ones that look like the familiar analog dials.

The Glass Cockpit

Brian France mentioned the idea of the “glass cockpit” back in July 2012. There’s a continuing fight within NASCAR about how much information drivers and crews should have – and how much of that information ought to be accessible to fans. It seems sort of silly that people are losing races because they got a pit road penalty for speeding. It’s frustrating for everyone involved.

Moving to fuel injection necessitated adding a number of sensors to the cars and integrating them into a single . Digital dashboards were tested back in April at Kentucky, but we’ve heard very little about them since them.

The term “glass cockpit” comes to us from aviation. By the 1970s, the average plane had over 100 gauges and dials. If you need a piece of information – the status of a wing flap, or your fuel level – you don’t want to have to search for it. It needs to be right there, at hand. A racecar isn’t as complicated as an airplane, but the amount of information the driver has access to is getting larger and larger.

Here’s an example of an early-2000’s era dashboard.


Recently, we’ve added a trackbar adjustment knob, too. It’s a lot to look at when you’re going 180 mph.

Here’s a helmet-cam picture from Kevin Harvick’s car. I included it because you’ll notice that the driver is looking through the steering wheel. If you go to the original video (, you can see that the gauges on the sides disappear from view when turning.


Not only can you not see all the information that’s there…  there’s a lot of information that’s not there. There’s no speedometer (I’ve explained that a tachometer is actually more accurate than a speedometer, but when you go to digital, that’s out the window.) There’s no lap time displayed, or cockpit temperature or fuel gauge or tire pressure or…

As NASCAR moves more and more toward technology, the drivers (and crews) will have more and more information available. This is good… up to a point.

How many times have you fumbled around all the menus on a piece of software looking for that command you know is there, but you never remember where it is?

When I’m coming down Pit Road for a pit stop, I don’t care about my lap time or my oil pressure or my fuel pressure. I care about one thing: Don’t speed. And this is one of the big reasons for the digital dash.

Information can be grouped into pages, displaying only the information that is relevant to the driver at that time.

Jamie McMurray tweeted a couple pictures of the digital dashboard during a tire test in Kentucky.

NASCAR_DigitalDash_McMurray2 NASCAR_DigitalDash_McMurray

Important note – it’s the same display in both pictures, just different pages.

A couple interesting things to note:

You can display information in different formats. Your driver is used to gauges? Sure. Note that in the upper picture, there is a red line, a green line and a yellow line right on the tach. A visual indicator for the driver when he or she is getting close to pit road speed or the engine speed at which the engine designers start to get nervous.

The lower display shows lap times! Right now, the driver depends on the spotter or crew chief for that information. And, of course, if you have a driver who doesn’t want to know, you just don’t put that piece of information on the screen.

It looks like the McLaren PCU-500N Digital Dash Display will be the only one allowed for competition. McLaren already makes a display unit (the PCU-8D) for F1. You can get an idea of the types of information they display in the video below.


Optional Now… Mandatory for 2016

ChadKnausAccording to the NASCAR Sprint Cup Series rule book, digital dashboard display

“may be used at all Events after August 5, 2015. Digital dash display use will not be permitted before August 5, 2015. Effective January 1, 2016, a digital dash display must be used at all Events.”

Why August 5th?  Some of the conspiracy theorists over on Reddit suggest that the significance of the date is that it’s Chad Knaus’ birthday.

It’s also Alan Gustafson’s birthday, but Gustafson won’t be using the dashboard in Jeff Gordon’s car this weekend. Why?

As Gustafson said on SiriusXM Radio’s The Morning Drive, the digital dash is about 5 pounds heavier than the analog dash they’re using now. The advantages of the digital dash don’t outweigh (literally) its weight penalty. Five pounds located up high in the car, is a pretty stout competitive disadvantage – until 2016, when everyone is required to run the new dashes.

Aug 052015

Well, it finally happened.

They made it so easy to make an infographic, even I — the least design-savvy person in the entire world — can do it.

It’s not perfect – the tool I used doesn’t seem to like fractions, so I couldn’t get it to give me any lines between 0 and 1 on the chart of how much fuel you need to complete a lap at different tracks – but hopefully the bars give you an idea.

Fuel Mileage Races Infographic

Jul 242015

Aerodynamics is complicated. Let’s just get that out of the way. But it’s not so complicated that we can’t understand what’s going on with just a little patience.

Why 3D?

Every wonder why they call it three dimensions? The reason it’s three is because I (or you) can denote any point in space with only three numbers. For example: a latitude, a longitude and an altitude. Since we’re dealing with much more limited spaces, a simple Cartesian Coordinate system, like this one, usually suffices.


The line that goes out to the point P is a three-dimensional vector. It’s got parts going in the x, y and z directions. By specifying that there is so much in the x-direction, so much in the y-direction and so much in the z-direction, I’ve told you everything you need to reconstruct that vector.

Forces in 3D

A force (a push or a pull) can act in any direction, but in order to understand the effect of that force, it’s easier if we break it down into its components – how much of the force acts in the x-direction, how much acts in the y-direction, etc.

When we do this on a race car, we give the different directions their own fancy names – just to make us seem extra clever. Basically, any force that acts in the opposite direction the car is going is called drag. Any force that pushes the car into the track is called downforce.

When the force acts up instead of down, it’s called lift. Yes, I know it should be called ‘upforce’, but the people who study aeroplanes named it.

Not shown in the picture below is side force, which would be in or out of the page.


Spoiler Alert!

Let’s think about the air acting on the spoiler. Because the spoiler is at an angle, the force on the spoiler is at the same angle (it’s perpendicular to the surface). So some of the force on the spoiler points down and some of the force points horizontally.

Which means some of the air hitting the spoiler creates downforce, and some of the air hitting the spoiler creates drag.


The more area there is for the air molecules to hit, the larger the force. A tall spoiler creates  more force than a short spoiler – but because of what I said up above, the angle of the spoiler is absolutely critical.

The more upright the spoiler, the more of the force is drag and the less of the force is downforce.  If the spoiler were horizontal, you’d get all downforce. If the spoiler were perfectly upright (vertical), all the force would be drag.

Why a Different Package for Indy vs. Kentucky?

In Kentucky, NASCAR went with a shorter spoiler to reduce the downforce. Passing has been a persistent problem at 1.5 mile tracks and the idea was that if the cars weren’t quite so dependent on aerodynamic forces, then the loss of those forces when you get close to another car wouldn’t have such a great impact.

And that strategy seems to have paid off well.

But Indianapolis and Michigan are very different kinds of tracks. At 2.5 miles and 2 miles respectively, they  are closer to superspeedways than they are to 1.5 mile tracks. At Indy and Michigan, the cars get going very fast down the straightaways, which lets the leading car get away from its pursuers. And it’s pretty tough to pass a car if you’re two lengths behind it going into the corner.

So the goal at these almost-superspeedway tracks is to slow down the maximum speeds along the straightaways so that a car can’t get away so easily. This is a little different than the goal at the intermediate tracks.

There’s a couple of ways to slow down a car: the two most obvious are

  • Decreasing horsepower
  • Increasing drag.

Decreasing horsepower introduces its own challenges, as we know from restrictor plate racing, so NASCAR is using the increased drag approach at Indy. And they’re doing that by setting the spoiler height at a pretty astounding 9 inches tall. At Kentucky, the spoiler had been reduced to 3.25 inches.

The best way to understand how much of a difference this is comes from a tweet from JGR Racing, which actually shows you the difference. Extra points for having gotten the product placement in there!


That’s a pretty big honking spoiler, eh?

But, you’re thinking (at least I hope you’re thinking) wait a moment… If they increase the spoiler height to increase the drag, aren’t they also increasing the downforce?

Yep. They are. It would be lovely to have a knob that you could turn and independently change the amount of front and rear downforce, and the amount of drag. But real life isn’t that simple.

Those Poor Engineers… NOT

The spoiler isn’t the only thing that’s changed. The changes in toto are…

  • 9″ spoiler
  • 1″ wickerbill (aka Gurney flap)
  • 2″ splitter
  • 43″ radiator pan width
  • speedway extension on the quarterpanels and rear bumper – the same ones run at the superspeedways.

So you’re thinking – my goodness, pity the engineers. All these changes.

Lemme tell you – the engineers are not upset. They love the opportunity to get ahead of the other teams by being smarter and figuring stuff out before someone else does. This is a chance for a team to get a win simply by understanding the set ups better than anyone else.

And something else to think about. In my column about Kentucky, I showed the changes in the spoiler and radiator pan sizes as a function of time. Well, I’ve updated those.

BSPEED_2015RulesChangesbyTrack_Spoiler BSPEED_2015RulesChangesbyTrack_RadiatorPan

The radiator pan is the exact same size at Indy as it was in 2014. The spoiler is only one inch taller than it was in 2014. And the teams have plenty of experience with the rear aerodynamic extensions from years of racing at Talladega and Daytona.

Yes, it does mean that they have to put those disparate elements together – which they haven’t done before – but the teams with the strongest technical staffs will be in the best position to take advantage of these just-in-time adjustments.

Personally, I’m psyched about track-specific packages. It gives the teams much more of a box to work in, which means they have that much more room to be creative. Looking forward to Indy!


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