azander

Hello all,

I'm wondering what the actual travel is on the clutch pedal. It is my understanding that there should be ~155mm total pedal travel including about an inch of freeplay before engaging the master cylinder. How much of the pedal travel is superfluous in disengaging the clutch? Does it actually have to be put to the floor and if so, how does the MPL slave work without requiring the pedal to be raised?

I essentially have a fused ankle (clutch foot), reaching the last 1" or so is difficult. I'd like to put a clutch stop and set the pedal to be as short as possible without changing to a 'heavier' ratio.

Thanks

FeralComprehension

If the MPL slave has lower effort then the stroke has to be longer; it's basic physics as the work required to disengage the clutch is the same regardless.

On my (stock slave) '64 I have to put the pedal to the floorboard for full engagement.

azander

Basic physics indeed. So does the pedal sit further out (couple inches or so) with the MPL slave or is everyone with one riding the clutch? hmm

John McM

I've just had my RS clutch replaced. The parts were correct but the clutch engaged very close to the floor. The fix was to source a slave cylinder with a rod 8mm longer tan the one currently in the car. Still need to research this, but the initial assumption is that you can change pedal bite with the rod length.

c didy

Most people seem to indicate that in their cars disengagement, eliminating all drag, is not complete until the clutch pedal is absolutely at the floor. It would be better if disengagement occurred before this extreme position to allow correct decoupling of the input and output during shifting. There is a TSB discussion of the appropriate throw adjustment since it has been a recurrent topic. In the past I have asked how to measure and adjust the pedal throw to meet spec per the Porsche TSB but it is still not clear how this is done. You may benefit from achieving this 155mm as a first step in any clutch arrangement.

JasonAndreas

Are you sure they used the correct release bearing?


Loosen the fasteners pointed at by the red arrows to move the pedal stop and then



a piece of string or a ruler.

c didy

Good enough. Thanks Jason.

Does this allow full clutch dis-engagement before completely depressing the pedal to the floor?

John McM

Yes, I checked that, they used the long tail.

azander

I found a spec sheet on a GT40 forum (G50 after all) comparing the stock Porsche slave vs the MPL unit. The required pedal travel is 4.45" to 5.7" for the MPL unit. This is based on a 5:1 pedal ratio which by a quick guesstimation and a ruler on my 993 pedal box, seems to be the same. I guess the MPL unit just distributes the useful work over the spec'd 155mm of pedal travel. If this is true I suppose I can use the stock slave with a longer rod to set the bite point higher.