NASCAR and Goodyear are ready for rain at a road course with rain tires. But is that all you need race safely and competitively in the rain?
Why Rain Makes Racing Hard
In sportscar racing, teams simply trade out their normal “slicks” (which have no treads) for rain tires. In NASCAR, at all course except road courses, we just stop and wait for the rain to let up.
Slicks 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 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 200 mph speeds.
the coefficient of friction tells you how grippy your tires are. The higher the number, the grippier the tire. Regular car tires have a coefficient of friction with dry asphalt between 0.7-0.9. That number drops when you make the asphalt wet — to as low as 0.25-0.50. (These numbers are 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.) Race tires on dry asphalt have coefficients of friction between 1.1 and 1.3 or so, but they drop even lower on a wet track.
Water gets between the tire and the road, decreasing friction and thus grip. Even a very, very thin layer of water can cause hydroplaning. The faster you drive, the smaller the contact patch, and the more likely you are to hydroplane.
Goodyear’s Solution for Racing in the Rain
Goodyear’s rain tires have grooves — just like passenger car tires. The grooves point away from the center of the tire in the middle. The pressure of the tire on the track pushes water away from the flat spots and into the grooves. The grooves give the water a way out from under the tire.
Goodyear supplies tires for other series, which has given them lots of experience with developing tires for racing in the rain. But it’s still a challenge.
In passenger cars, hydroplaning can happen at speeds as low as 35 mph. In the 2008 Montreal Cup race, the average speed went from 90 mph to 75 mph when the rain tires went on.
Other Rain Considerations
In addition to tires, there are some other issues with racing in the rain, most of which have to do with visibility. All the traction in the world doesn’t help if you can’t see where you’re going.
Windshield wipers have to do a whole lot more work on a race car. Because high speeds mean that more spray from cars in front of you hits your windshield.
You also have to worry about tear offs, because you’re still going to get gop on your windshield. Your wipers have to work with the tear-offs.
Remember Carl Edwards at Montreal in 2008 with a Swiffer mop trying to clear the fog from the inside of his windshield? Moist air will condense on any cold surface. Windshields are made of good thermal insulators, so it’s inevitable that you are going to get condensation.
A defogger uses heated air to increase the temperature of the windshield to prevent condensation. 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. That’s a lot of stuff to cram into a stockcar.
Race cars don’t usually have brake lights, although they have been used. In the aforementioned Montreal race, Joey Logano wrecked under caution when someone stopped in front of him and he didn’t see them.
And, of course, if we give the drivers brake lights, they will start playing mind games with each other.
Rain, as you know, is often accompanied by thunder and lightening. Lightening killed one fan and injured several more at Pocono in 2012. The drivers are good: They’re essentially in Faraday cages. Your car is one of the safest places if you’re stuck outside in a thunderstorm. But spotters, pit road officials, etc. are all out there in the elements. Pit crews face additional hazards, including slipping (them and/or the car).
Can stockcars race in the rain? They can, under some limited conditions. But it’s much harder for the drivers, the crew and everyone involved. Sometimes, the smart thing to do is wait and hope the rain delay is shorter rather than longer.
NOTE: I spiffed up this blog was spiffed up on 2020-10-08 by editing it for clarity and length.