The National Hot Rod Association (NHRA) sets the rules for roll bars and roll cages for racing vehicles. Without the roll bars or cages, drivers are not allowed to race. The NHRA has made finding and following the rules easy, and there are several race enthusiast magazines and businesses to help a driver get his ride ready to race. Check with the racetrack to find out if their rules are stiffer than the NHRA's basic rules.
The NHRA requires a roll bar in every convertible that is 13.49 seconds or quicker in the quarter mile. For cars that are not convertible, their cut-off time is 11.49 seconds in the quarter mile. There is an exception to this rule. If the vehicle has the stock firewall and floorboard intact, it can run the quarter mile in as little as 10 seconds. The roll bar has to be constructed with 1 3/4-inch mild steel tubing with a wall thickness of 0.118 inch. Or 1 3/4 chrome-moly tubing with a wall thickness of 0.083 can be used.
The roll cage is similar to the roll bar, except there is more protection for the driver. Vehicles that run faster than 10.99 seconds in the quarter mile or have a modified floor and firewall must have a roll cage. Any vehicle, regardless of modifications, must have a roll cage if it hits 135 mph or faster in the quarter mile. It is important to note that roll cages must be certified by an NHRA chassis inspector. Contact the NHRA to find an inspector in your area.
At each race, a safety inspector or tech inspector looks at each vehicle and decides if it is fit to race. The inspectors look not only at roll bars and cages, but for other safety features as well. This includes items like helmets, radiator overflow reservoirs, lug nuts and studs, as well as a host of other equipment. The NHRA has set up the rules so that each safety step is built on the one that comes before it. For instance, if a racer has the roll bar but then moves up in speed brackets, he can add the cage to the existing roll bar structure.
