clutch question

[gnc]

i wonder if someone can help,
i have bmw zf 310 gearbox mated to a lexus 1uz v8 with a PMC adaptor kit and a standard sachs clutch, im using a 0.625 bore master cylinder, i did try a 3/4 bore master cylinder but i found it was too heavy. i still find the clutch heavy but with a longer travel . I would have thought a bmw clutch would be lighter than this
any thoughts on this or fitting a vacuum assist kit of some type.

[stevieturbo]

Have you verified how much travel at the diaphragm fingers you have, with respect to an OEM car ?

You may well still have leverage issues if you're moving something too far

I would think a larger bore master with the same pedal leverage ratio would be heavier ? As you're forcing a lot more fluid for any given pedal travel

If you wanted lighter, you would need a smaller master....but again, ultimately whatever set of "ratios" you need....you need the correct amount of travel at the clutch fingers themselves.
And this may require more pedal travel ( or not...but you need a baseline somewhere )

I wouldn't imagine any OEM clutch should be heavy, but obviously different users will have different perspectives on that. Unless there is some weakness in the leg, it just sounds like your leverage setup is just wrong

So start from the clutch fingers and work back. How much travel do you have now ? And how much should it be ?

But yes there are servo options for assistance if there is a genuine need.

[gnc]

thanks for the reply, yes i realise all this, what im saying is im surprised a bmw clutch is so heavy, iv had bmw s amongst many other cars and non as heavy as this, ( except for my c3 corvette )

[gnc]

thanks for the reply, yes i realise all this, what im saying is im surprised a bmw clutch is so heavy, iv had bmw s amongst many other cars and non as heavy as this, ( except for my c3 corvette )

[stevieturbo]

gnc said:

thanks for the reply, yes i realise all this, what im saying is im surprised a bmw clutch is so heavy, iv had bmw s amongst many other cars and non as heavy as this, ( except for my c3 corvette )

If pedal/hydraulic ratios are wrong, then it may feel heavy because things are wrong.

Unless you've fitted this clutch to the car it is designed for.....where I would assume the pedal is not heavy. Then the problem is your install, not the clutch

But again, "heavy" can be subjective.

You need that essential baseline. How far are the fingers moving, vs how far should they be moving ? Then work back