rain tires
Treaded tires used on a wet track. Also referred to as wets.

rev limiter
Electronic/computer device in the engine controls which causes a controlled engine misfire if engine revolutions per minute (rpms) exceed the limit set by Indy Racing League rules. The legal rpm (or rev) limit for 2003 is 10,300 rpms. The rev limiter is used primarily to control speeds, thereby increasing safety and controlling costs.

ride height
The distance from the bottom of the chassis to the ground when a car is at speed. Indy Racing League rules stipulate that the ride height of the sides of a car should be 2 inches off the ground for all tracks.

riding the rails
Taking the outside line around a corner.

restrictor plate
An aluminum plate that is placed between the base of the carburetor and the engine’s intake manifold with four holes drilled in it. The plate is designed to reduce the flow of air and fuel into the engine’s combustion chamber, thereby decreasing horsepower and speed.

roll bar
A frame or cage of padded tubular steel that prevents the car’s roof from collapsing and protects the driver if the car rolls.

round
Slang term for a way of making chassis adjustments utilizing the race car’s springs. A wrench is inserted in a jack bolt attached to the springs, and is used to tighten or loosen the amount of play in the spring. This in turn can loosen or tighten the handling of a race car.