Can We Race Stockcars in the Rain?

In sports car racing, the only discernible change the viewer sees when it rains is that the normal “slicks”  (which have no treads) are changed out for rain tires.  Thus the calls for NASCAR to develop a rain tire good enough to allow us to continue races, even when it rains.

The surface of slicks (shown at left; from the Goodyear site) are flat sheets of rubber that maximize how much rubber is gripping the road at any given time.  The contact patch (the part of the tire in contact with the road) for a NASCAR tire on a Sprint Cup car is about the size of a man’s size 11 average width shoe — which isn’t all that much considering that those four tiny patches of rubber are responsible for producing 200 mph speeds.

The number that tells you how grippy your tires are is called the coefficient of friction:  The higher the number, the grippier the tire.  For regular car tires, the coefficient of friction between dry asphalt and rubber ranges from 0.7-0.9, depending on the specific surface.  When you make the asphalt wet, that can decrease the coefficient of friction down to 0.25-0.50.  (These numbers are all ranges because the specifics – the type of asphalt, how old it is, the oil content, the specific type of rubber, etc. all affect the coefficient of friction.)  For race tires on dry asphalt, we’re looking at coefficients of friction between 1.1 and 1.3 — or so I’ve been told, because tire companies keep that type of information under wraps.

TiresContactAs I’ve tried to show at right, water gets between the tire and the road, which decreases friction and thus decreases grip.  All you need is a very, very thin layer of water and you lose your grip.  You’ve probably heard the term hydroplaning – there is a plane of water between your tires and the road.  The faster you drive, the smaller the contact patch area and thus the faster you drive, the more likely you are to start hydroplaning.

Rain tires are made with grooves (as shown below) – just like  tires made for passenger cars.  The grooves point away from the center of the tire in the middle.  The pressure of the tire presses the water away from the flat spots and into the grooves.  The grooves give the water a way out from under the tire.

The Nationwide series at Road America will have rain tires on hand, but the Sprint Cup Race at Sonoma will not.  People have always wondered why you would do this for one series and not for the other.

Reasons to Race in the Rain

1.  The fans.  How many people spend all year anticipating a race, only to have the race postponed and they can’t stay for the following Monday because they have to work or have other obligations?  There’s a lot to be said for making sure that races are run the day they are scheduled.

Reasons Not to Race in the Rain

1.  Windshield Wipers.  When it starts raining, I’m guessing the first thing you do is to turn on the windshield wipers.  On a race car, you have to have a motor and a post available on the car so that a wiper could be mounted.  That’s not so difficult, but the teams can’t really head out to Auto Zone and buy windshield wipers.  The wipers would have to stand up to high speeds.  Ever gone through the dryers at a car wash and watched your windshield wipers get pulled off the windshield?

Another issue is that the windshield wipers would be much trickier to use effectively at high speed.  Remember that you go about a football field a second at 200 mph.  The rear tires of the race cars throw up a huge amount of spray – the windshield wipers would have to run pretty fast.  If you’ve ever reached for your wiper speed control and found that it was maxed out, you know that there’s a limit as to how fast the wipers can go and still be effective.  Sometimes, there’s just too much water coming down to remove.

Finally, if you’re going to use tear offs, you’ve got to have a wiper material that works with tear offs.  I don’t see how you can eliminate tear-offs unless you were positive it would rain the whole time — and even then, the rain isn’t going to wash all the track debris off your car.

2.  The Swiffer Effect.  Remember Carl Edwards at Montreal in 2008 with a Swiffer mop trying to clear the fog from the inside of his windshield when they tried to race in the rain there?  When the air is moist, it will condense on any cold surface.  Glass tends to be much colder than other parts of the car because glass is a good thermal insulator.  When it’s moist, you get a thin layer of fog on the inside of your windshield.

A defogger uses heated air to increase the temperature of the glass so that the water doesn’t condense on the glass.  You need a heater, ductwork and a blower.  Most passenger car systems also pass the air through a dehumidifier so that you’re not making the problem worse by increasing the moisture content.

3.  Brake Lights.  Coming over the Cumberland Pass this morning, I encountered a lot of fog in the mountains.  It’s beautiful, but really hard to see through.  In Maryland, people turn on their hazard blinkers when the weather gets like that so that you can see them more clearly.  Race cars don’t even have brake lights.  In the afore-mentioned Montreal race, Joey Logano wrecked under caution when someone stopped in front of him with no warning.  Not only do race cars not have hazard lights, they don’t even have brake lights.  If we give the drivers brake lights, they are likely to start playing mind games with each other using the brake lights, so perhaps that’s an area we don’t even want to go.

4.  The Fans.  I was at Petit Le Mans in 2009 and I can tell you first hand that being out there trying to cover a race in a monsoon was not even close to fun.  I spent ten hours in a damp firesuit with wet feet.  My notes got so wet I couldn’t make half of them out.  Do you really want to sit for three hours in the rain — even a light rain — trying to watch a race that you may or may not even be able to see because of the moisture?

5.  Safety.  Rain often is accompanied by thunder and lightening.  Lightening is dangerous, as I wrote about after a fan was killed and several more were injured at Pocono in 2012.  You’ve got tens to hundreds of thousands of fans, often seated at high points and surrounded by metal.  That’s a disaster waiting to happen.  Pit crews face additional hazards, including slipping (them and/or the car).

6.  The Drivers.  There is something to be said for experience.  Novice drivers make a lot more mistakes, even if they are being as careful as they can be.  I know… NASCAR drivers are the best in the world… but very few NASCAR drivers have  experience racing in the rain.  There are going to be accidents.  Since the tires are responsible for making any directional changes, wet tires are going to make it harder for the driver to make sudden changes in speed and/or direction, which means they will have a harder time avoiding accidents.

7.  The Racing.  In passenger cars, hydroplaning can happen at speeds as low as 35 mph.  The higher the speed, the more likely you are to have hydroplaning, so racing in the rain means lower speeds.  In the Montreal race, the average speed went from 90 mph to 75 mph when the rain tires went on.  Racing on an oval in the rain would probably look like a funeral procession when they cars aren’t busy crashing into each other.  Remember that the series that race in the rain race a lot more road courses and have a lot more downforce.  The increased downforce allows them to keep the speeds a little higher than you could with low-downforce stock cars.

Stock cars weren’t designed for racing in the rain.  Could they be?  Sure – the technical challenges can be overcome given enough time and money.  Goodyear would probably have to invest some money in research and testing to come up with a tire optimized for wet stockcars.  Motors, blowers, wipers, etc. could be designed and tested.  But you’re still left with the question of whether a race in the rain can be just as good as a race without rain.  I think not.  Add in the safety concerns, and it seems like the smartest thing to do when it rains at a NASCAR race is still to stay indoors.


Sprint Car Safety

NASCAR fans are used to having our drivers walk away from spectacular crashes.  Unfortunately, we are reminded all too often — like last night — that racing, regardless of all the technical improvements we’ve made, remains a dangerous sport.  As you move from the top-level Indy and NASCAR series, the number of driver deaths increases.  Some of the higher risk level is because of the funding – racers running on much smaller budgets tend to want to put their money into making the car go faster rather than buying more/higher-quality safety equipment.  Sanctioning body requirements are also not as rigid

Sprint Cars (like the one shown at right) are tiny, very powerful racecars.  The 410-series uses a 410-cubic-inch V-8 engine that generates 800-900 hp.  For comparison, NASCAR Sprint Cup engines are 358 cubic inches and generate around 900 hp; however Sprint Cars are about half the weight of a NASCAR car.

You’ll often hear people talk about power-to-weight ratio.  For a NASCAR Sprint Cup car, the power-to-weight ratio is 900 hp/3480 lbs = 0.26 hp/lb.  (I know, those aren’t standard units, but they’re more accessible than W/kg.)   Taking a weight of 1575 lb (including driver) for a Sprint Car (I’m finding all kinds of numbers on the web for required weight), the power-to-weight ratio for a Sprint Car is 850 hp/1575 lb is 0.54 hp/lb.  Just for reference, Wikipedia lists the power-to-weight ratio for a Funny Car Drag Racer at about 3.3 hp/lb.  A street Corvette Z06 is about 0.16 hp/lb.

That’s an awful lot of power for a very light car and Sprint Cars need aerodynamic help to stay planted on the ground.  That’s the purpose of the giant wings on the top and front.  The wing at top is about 5 foot x 5 foot and the wing  over the front wheels is about 2 foot x 3 foot.  Those giant areas give air molecules plenty of places to hit and push the car into the ground, thus generating a lot of downforce.

SprintCarChassisSprint cars are smaller (they have a 84″ wheelbase, while the NASCAR Sprint Cup cars have a 110″ wheel base), but they have the same type of tube frame construction as stock cars.  They also have a relatively high center of gravity, which makes them much more prone to tip over than other types of cars.  For the gearheads among you, Circle Track does an absolutely great job with tech details.   NOTE:  Although the wing does raise the Center of Gravity, the issue is not just with the wing:  wingless Sprint cars have the same issue with a high CG.

Sprint Cars reach a maximum of about 140 mph, which is a combination of the very powerful engine, the light weight, and the huge amount of drag that the wings create.  Using the max speed of 140 mph, a Sprint Car has the same kinetic energy (aka energy of motion) as contained in a third of a pound of TNT.  Energy is critical because (as you no doubt have had pounded into your head), energy cannot be created or destroyed – it can only change forms.

There are two critical factors in crashes:  How much energy you’re carrying when you crash (your kinetic energy) and how that energy is transformed into other kinds of energy.  For example, when a car pulls into the pits on a green-flag pit stop, its kinetic energy is slowly transformed into other forms of energy:  heat (brakes, the tires if you skid them), light (brake rotors glowing), and even sound (squealing).  It’s a slow, controlled transformation of energy from kinetic to other forms.

When you crash, energy is transformed into different forms.  Energy may be transformed into spinning or skidding motions of the car, the noise of tires squealing — or sheet metal crushing.  The one place you do not want to dissipate energy is through your driver.

The amount of energy is important, but so is the time over which the energy transformation happens.  The force you experience when you change speed is proportional to the change in speed divided by the time it takes for you to change speed.  I like to say that it’s not how fast you go… it’s how fast you stop.


The airbag in your car works on the principle of slowing down how fast your head comes to a stop.  If you extend the time it takes for your head to stop from a tenth of a second to a second, you experience ten times less force.  This is the principle behind how SAFER barriers work:  They flex when hit slowing down the car in a much gentler way than a concrete wall.

It took four deaths between 2000 and 2001 for NASCAR to put their considerable brain power to making revolutionary changes in safety.  The folks at the NASCAR R&D Center are concerned about racers at all levels of stock car racing, from the Sprint Cup down to the local tracks.  Some of their research – like the development of strong tube-frame chassis and solid construction methods – are transferable to open-wheel racing; however, there are some unique challenges to improving safety for this type of racing.  There are also people like Randy LaJoie, who work with racers in many of the lower series and are just as concerned about short track racers as they are NASCAR drivers at the top level.

Sprint Cars race at a lot of tracks that do not have SAFER barriers.  Installing SAFER barriers is very expensive and many smaller tracks are struggling to stay open during the economic challenges of the current era.  Maybe this is a place for someone to design a lower-cost SAFER barrier that doesn’t need to meet the requirements of a Daytona or Indy.  Sprint Cars race at many highly banked tracks — when you combine an incline with a car having a high center of gravity, you get cars flipping over.  Lowering the CG of the car would go a long way to keeping them on the ground.  An additional complication is that there are a slew of sanctioning bodies for Sprint Car racing, which complicates any type of unified action.  It was easy for NASCAR to put their considerable economic heft behind an edict that all tracks they race at must have SAFER barriers.  It will be much harder for a similar effort at smaller tracks and multiple sanctioning bodies.

Perhaps the tragic loss of Jason Leffler will be the catalytic incident that spurs a safety initiative for Sprint Car racing similar to the one NASCAR initiated in 2001.  I can think of no greater tribute to a driver than that his very untimely death ends up saving more lives.  Thirty-seven is just too, too young to go.

NOTE added:  As I noted above, the win provides a LOT of aerodynamic downforce and drag.  This does help the car be more stable; however, it does not address the problem that, in high banked turns, a high center of gravity make a car more probable to tip over.


Toyota Engines: By The Numbers

There are somewhere in the vicinity of 840 parts in a NASCAR Sprint Cup Engine (at least the Chevy version and yes, I am taking someone’s word for this.  I did not have time to sit down and count all the pieces.)

The relevance of this is that if any one of those pieces doesn’t do its job, the car it is in will be headed for the garage.   This year, Toyota Racing Development (TRD) engines have suffered from one of the highest failure rates see in the series.  I pulled together data from the first thirteen races of 2011 and 2013.  2011 was the last year Joe Gibbs Racing (JGR) had its own engine program – they switched to TRD engines in 2012 because of an abnormally high failure rate in JGR engines.

Let’s look at the numbers for the first thirteen races in 2011 and 2013.  thanks to for the numbers and to for their charts that show who was using what engine maker what year.

Manufacturer 2011 2013
Made % Failed Made % Failed
Earnhardt-Childress (ECR) 105  6.7 91 0
Roush-Yates (RY) 130  1.5 166 2.4
Toyota Racing Development (TRD) 68 1.5 81 9.9
Hendrick (HMS) 79 1.3 142 1.4
Penske (PR) 39  0
Joe Gibbs Racing (JGR) 39 7.7 (13%)


The number of engine suppliers is shrinking, since Penske went to Roush-Yates in 2013 and Joe Gibbs to TRD.  Note that ECR lost Earnhardt-Ganassi Racing to Hendrick as well.

The engine failure rate shown in 2013 for JGR (13%)  is the fraction of TRD engines that were in JGR cars when they failed.  In actual numbers, Toyota’s lost 8 engines this year, 5 of those being JGR.  (JGR uses just under 50% of the Toyota engines.  Mind you, we’re dealing with small numbers here.  It’s worth noting that JGR ended the 2011 season with an overall failure rate of 5.6%.

But what about results?

JGR: 2011 vs. 2013
2011 2013
Wins 2 (15.4% of all wins) 5 (38.5% of all wins)
Top 10 finishes 14 (36% of all starts) 19(49% of all starts)
Laps Led 1078 (25%) 2053 (34%)
Top 10 qualifiers 19 (48% of all starts) 28 (68% of all starts)

Up in all categories.  It’s a little hard to compare too much else between 2011 and 2013 because of exigencies:  Kenseth’s penalty, Hamlin being out of the car and Logano vs. Kenseth in the 20 car.

So does that mean Toyota’s high engine failure rate isn’t a problem?  Right now, it’s really not an issue; however, we’re still in the 26-race segment to qualify for The Chase.  Now is the time to learn and experiment because a mistake isn’t as costly.  You just need to make sure your drivers are in the top 10 – although it’s nice to be first at the end of the first part of the season, it doesn’t mean anything when they are handing out awards at the season’s end.

Things change once The Chase starts.  During the long part of the season, each race is 1/26th (4%) of your total race-for-the-chase score.  In the chase, each race is 10%.  Mistakes in the chase are much more fatal than mistakes during the regular season.