Several forms of motorcycle racing exist, and for each one, a specific motorcycle must be built. One such form of racing is pro stock motorcycle racing, and a specific bike must be built to accommodate the speeds reached by these bikes. A pro stock bike is the motorcycle equivalent of a pro stock car; they are overbuilt to go fast and straight, and they must have a rear roll bar to prevent the extremely powerful bike from flipping over backward.
A pro stock bike is built solely to drag race. The wheelbase of the pro stock bike is much longer than most motorcycles, to accommodate the rapid acceleration. Since this type of motorcycle will not be doing any sharp cornering, the frame does not need to be short to allow such turns. On many pro stock bikes, the wheelbase—the distance between the front and rear wheels—is often adjustable and can be customized for certain race tracks or conditions. Popular models have a suspension fork on the front of the bike to absorb shock, but the rear of the bike is usually a rigid frame with no suspension. This prevents loss of speed and power to flex in the suspension.
The components of the pro stock bike are very sophisticated. Most bikes have five speed manual transmissions that are shifted using an air shifter, which is operated by a button mounted on the handlebar. An on-board computer monitors the function of the engine, and after the race, the computer can tell the rider what aspects of the engine's performance need to be adjusted for the next race. Extremely wide tires are mounted on the rear of the bike. They are made of thick rubber compounds and are typically good for seven or eight runs down a track.
The engines on a pro stock bike vary in size and components, but many are as large as 350 horsepower. Records have been set on bikes that reach from 0-60 miles per hour (0-96.5 kilometers per hour) in one second, and 0-100 miles per hour (0-161 kilometers per hour) in two seconds. They can reach speeds of almost 200 miles per hour (322 kilometers per hour) on the track, completing the quarter mile run (.40 kilometer) in 6-8 seconds.