Camber: Searching for The right angle
August 27, 2013, Ron Lemasters Jr. for NASCAR.com, NASCAR.com
If you’ve ever looked at a NASCAR stock car, sitting quiet and peaceful in the garage area, you’re at once taken with the sleek lines, the feeling of barely restrained power and the utter coolness of the machine before you.
Then, you take a close look at the front wheels and say to yourself, “Man, this thing is all catawampus! Look at how the front tires are all bowed out at the top!”
Sorry to spoil the illusion, but … it’s supposed to look like that.
It’s called camber, and it’s just as important as tire pressure, sponsor logos and fuel cans.
What is camber? Glad you asked!
Camber is, simply put, the vertical tilt of a wheel. If it’s bowed out, it’s positive camber, and if it’s bowed in, it’s negative camber. Zero or neutral camber is when the wheel is straight up and down.
Why is this important?
If you want to have any grip at all on an oval track, you’ll bow those front tires out so they look like Dumbo’s ears. Your passenger car (or truck; this is NASCAR, after all) has a smidgeon of positive camber built in at the factory.
Camber is all about surface area. The more you have, the better you grip the road. Considering that the average contact patch on each of the four tires in your favorite driver’s hot rod is about the same area as the sole of a men’s size-11 shoe, you’re looking for all the surface area you can get.
In a perfect world, the tires would have all of the tread on the road. That can happen, if the road is perfectly level and straight. If you’ve ever been on I-20 headed to Talladega, you’ll realize this is not often the case. They’ll get it finished eventually … I hope.
Even if the road is perfectly level, which it usually isn’t, because engineers build a crown into most of them to help shed water to the shoulder, you’re not guaranteed a good deal of grip. In a race car, there’s banking to deal with, and it’s not perfectly level. That’s why that skosh of positive camber is built into your car -- to help it turn.
When you turn the wheel in any car, the laws of physics take over. Turn left, as you do into Turn 1 at Atlanta Motor Speedway for instance, and everything in or on your car keeps wanting to go to the right. Centrifugal force is a law unto itself. That means the tires are wanting to go right as well, continuing the path they were already on. That means less grip.
NASCAR racing these days is all about grip: mechanical or aerodynamic, force is force and more is better. One of the ways crew chiefs generate grip is with camber.
OK, we’re in the corner, foot to the floor, feeling our car trying to go straight because of the tremendous lateral force on the outside pair. Here’s where it gets magical.
The right-side wheels have a touch of negative camber, while the inside wheels have positive camber. The right side tires are always on the outside on an oval track, and as such provide more grip with some negative camber. The inside tires, which always lose grip when cornering, use the positive camber to catch up with the outsides in grip.
With the evolution of the Gen-6 car, NASCAR also allowed teams a limited amount of camber in the right rear to help it turn. Contrary to popular belief, there’s not a whole lot of flex in the steel tube-frame chassis the sport requires, and that means physics are having their way with the car in the middle of the corner.
With limited flex, the force is unable to transfer and results in a pushing condition. Pushing is when you turn the wheel left and the car just keeps on going to the right. Road-racers call it understeer; NASCAR folk call it “pushing like a dump truck.”
Camber is a great addition to the crew chief’s tool kit, but like most magic bullets, it can backfire.
If you put too much camber in either way, you’ll run the risk of damaging the tires. Racing tires, like the Goodyear Eagles the NASCAR Sprint Cup and Nationwide Series use, are constructed with all this in mind, but there are limits.
The tires are built around a nylon carcass, with overlapping steel belts and rubber in layers. Once the rubber is gone, there’s just nylon and steel interwoven. Once there’s a hole in that, there’s nothing but the inner liner, which looks like a giant, matte-black donut. After that, there’s air, asphalt and the sound of crunching metal.
There’s some flex in the tires, just as there is spring rate, and that helps determine how much you can run. There’s also a NASCAR limit on the amount of camber you can run, and it tends to be conservative. Plus, if there’s too much camber, positive or negative, you’ll lose speed down the straightaway, not to mention a decrease in handling.
The idea of camber is to get the wheels as close to flat to the surface of the track as possible. That way, you can achieve optimum grip. Combined with air pressure, the tires are working at high efficiency when the angle is just right.
So that’s why the cars look like they do. Remember this when they go hauling into Turn 1 at Atlanta at nearly 200 miles per hour: the only thing holding them to the ground is four size-11 men’s shoe soles. Camber makes it better.