No racer would attempt to use a truck on a race since they are too big. They might be as fast as a car or even faster, but the size of the vehicles makes them not a good vehicle for a race. This would only result to accidents since people would be afraid and when that happens, there might be chaos on near the race track. Sponsors wouldn't like that at all as they are going to take the blame for any accident that occurred. That is why; trucks are use in racing. Besides such vehicles would be hard to maneuver and you would need to maneuver your car all the way to the finish line in any racing event that the racer participated in.
Using truck in a race would be impossible in the real world, but everything is possible in the gaming world. Wait till the signal is given and drive your truck as fast as you can till you reach the finish line. Pick some weapon along the way and use it on your rivals on the race. Try not to get out of road since that would equivalent to an instant violation. Also try to avoid anything that your rival throws at you since it is an instant death on your part.