CLUTCH DRIVER SIZE

There are many factors that decide what clutch driver you should run for a given application. Unfortunately, there are not any blanket answers that work in all tracks and conditions. There are, however, some rules that will help you to make the best decision.

Why do large versus small clutch drivers affect my lap times? My gear ratio is the same?

This is a common question. A larger clutch driver forces the chain to travel a longer distance around the crankshaft of the engine. This decreases chain drag, since the chain is making its change in direction more slowly. It has a lower tangential acceleration in this manner. This often gives the kart more top speed, because less energy is being consumed by the chain. The drawback to this is that since the chain is farther from the crankshaft, there is a higher polar moment of inertia. In short, the chain feels heavier to the engine, and it has to work harder to get it up to speed.

A smaller clutch driver works in the opposite manner. The chain is quickly accelerated around the crankshaft and the kart will have more "pull" off of the corner. On the other hand, the chain will have more drag at high speeds and the kart will suffer in that manner.

How to make sure you have the correct driver is a funtion of the driver's preference, chassis setup and track conditions, but often, one can take advantage of the effects of the driver size to compliment your chassis where you are fast, or to speed you up where you are getting pulled by the pack. Good luck racing! Kermit Buller