27. Overall weight of the vehicle can affect how fast timing can come on. For example, the lighter the springs, the faster the timing goes from initial to total timing. Too light of a spring on a heavy truck can ramp the timing up too quick and cause a pinging noise or what is know as detonation. In this case, switching one light spring for a slightly heavier spring might solve the detonation by allowing the rpm to be higher before the mechanical advance reaches total timing.