Correctly set your clutch
Compiled by Greg Wilson
A large amount of “gearbox problems” are actually experienced by the incorrect adjustment of your clutch.
If this is set incorrectly it can also cause long term damage to your pressure plate and gearbox making for frustrating and expensive racing.
There are three symptoms that can be caused by this incorrect adjustment.
Difficulty changing gears (usually hear grating), especially when changing from 3rd to 2nd. This is caused by insufficient depression of the pressure plate and thus does not disconnect the motor from the gearbox. This means the syncros have to work twice as hard to equalize the speed of the pinion and main shaft in the gearbox to successfully engage gears. This prematurely wears out your syncros as well as causes your engagement gears to grate and wear out.
Sloppy clutch pressure, sometimes the clutch has to be pumped to get it to properly disengage. While this could be air in the system, for the purpose of this guide I will assume that the clutch has been properly bled. This causes slow gear changes and often symptoms similar to Symptom 1 described above.
Pressure plate cracks or the release leavers tear off their pivot points. This will cause complete pressure plate failure and the inability to finish your race!
Correct adjustment of your slave cylinder and clutch peddle stopper will correct the issues experienced above.
The first item that needs to be checked is the play on the slave cylinder. What you need to do here is push the pin that the slave cylinder actuates directly back towards the slave cylinder. There will be some resistance here as there is a spring in the slave cylinder. Once you feel that the pin has hit the back of the slave cylinder and go more there should be no more than a 5mm gap between the clutch arm on the gearbox and the pin that you have pushed back. If there is a bigger gap than this then when driving the pressure plate will push the slave cylinder back causing the sloppy or soft clutch pedal. When you pump the pedal it takes up the play.
It is important to have a peddle stopper to prevent the over depression of the clutch which overworks the pressure plate and causes the ultimate failure of the pressure plate. Tip : this also speeds up your gear changes!
While having a peddle stopper it is important that you adjust it so that it allows for enough peddle travel and allows for full disengagement of the clutch. The best way I have found to do this is to put the car in gear. Have a mate push the car forward, the car should not move. Slowly push the clutch peddle in until the clutch releases and the car rolls forward. This is the bite point. From there adjust the peddle stopper to allow for an additional 20mm of travel past the bite point.
This additional travel is needed to allow for the brake fluid getting hot or small bubbles forming in the fluid etc.
I hope this how to guide makes sense and makes you’re racing that much more rewarding.