What We Need to Know to Build your Race Clutch

Apr 7, 2020 | Clutches, Racing

When putting together your race car, the clutch is often one of the final pieces that brings everything together. For a clutch to perform well it has to have enough capacity to handle your combination – the engine, chassis, gearing, and tires. Too little capacity and your clutch will have a very short life with disappointing results and elapsed times. As a general rule, it is always better to have a little more capacity in your clutch system than you need. Always consider the load factors below in selecting a clutch system:

  1. Engine – we need to know a little about your engine. How many cubic engines is it? What is the horsepower and torque of the engine? Even if you do not have precise dyno numbers, a solid estimate will help. Lastly, we need to know the intended operating RPM of the engine – what the RPM will be when shifting and leaving the starting line.
  2. Chassis – it is important to know how much the car weighs (with driver) even if it’s a close estimate. Is this a complete tube chassis car or a back half car?
  3. Tires – what size tires are you planning to run along with the rollout of the tire? The tire is what is applying the grip to the racetrack, and ultimately provides the load back through to the clutch system.
  4. Gearing – what are the rear end gear and the transmission ratios? Ultimately, the rear end gearing should be determined through the engine operating RPM, car weight, and tire size so that you cross the finish line at the upper limit of your desired RPM range. The transmission should then be geared to optimize acceleration and traction through low gear with the subsequent ratio drops in each gear keeping the engine in the optimum RPM range.
  5. Other factors such as rear shocks, struts, four link settings, and tire pressures will also affect your clutch system, but they should be able to be worked around in the clutch adjustments if you have properly applied the information from the engine, chassis, tires, and gearing above.

Lastly it is always good to understand your expectations of the clutch system as well. With a clutch system that is frequently serviced like a Pro Stock Car, you can push the capacity harder (smaller size, less plate load) because it is constantly being maintained. In other applications where the clutch is serviced periodically, you need more capacity (larger size, additional pressure) so the clutch system will provide a more consistent and longer period of use between servicing.

If you have further questions about selecting the right clutch system for your race car, please reach out to us at [email protected].