Stiff clutch pedal

[JerryBoone]

Last spring when it was time to put my 1969 S4 DHC back on the road, I discovered a puddle of fluid from the clutch master cylinder beneath the car (and onto the footwell carpet).

I decided to renew everything. I am using a 5/8-inch master cylinder from Wilwood, a 3/4-inch slave cylinder from British Parts Northwest and a new steel braided line from Dave Bean.

The clutch pedal comes in very close to the top of its movement and engages/disengages well.

But it takes a whole bunch of pressure to push it...enough that at a traffic light my left leg often begins cramping up and I have to shift to neutral and take my foot off the pedal.

I don't remember it being that hard before I installed the new parts.

The only thing that is different is the steel braided line, but I'm hard pressed to think that can be the cause of the stiffness.

I'm open to suggestions. All will be appreciated. Thanks.

[elans3]

Smaller slave cylinder required by the sound of it !

[gjz30075]

I'm pretty sure the slave should be 7/8".

[alan.barker]

The Slave should be 7/8" Dia
Alan

[Lotus54]

The slave on mine failed- I found a 3/4” new slave and installed it. ( I do have larger one and now parts to rebuild original). It was stiffer than original, but disengaged better.

[alan.barker]

The slave on mine failed- I found a 3/4” new slave and installed it. ( I do have larger one and now parts to rebuild original). It was stiffer than original, but disengaged better.

I'm not sure if it would disengage too much and if that is good for the Thrust Bearings on the Crankshaft.
Alan

[Lotus54]

There is a fair amount of ‘slop’ in the pedal/rod area. So I think fine. Engagement is not much different location than before. Eventually I will swap in the new proper one. Although this one claimed to be for Lotus Cortina and Elan. I do not think the throw is that much different, but I also did not measure. It also was not that much different in foot pressure- at least to my uncalibrated leg.

Mark

[alan.barker]

Ok,
For sure the 7/8" dia Slaves are more expensive than the 3/4" dia
Alan

[Phil.C60]

The difference between a 3/4" slave cylinder and a 7/8" one with he same master cylinder is really quite a lot.
The 3/4 bore cylinder has a cross sectional area of .4418". The 7/8 bore is .6013" which is a 27% difference. That's quite a big reduction in pedal weight.

[2cams70]

If you use a smaller bore slave cylinder the travel of the release arm will be more than when using the correct one. You could therefore potentially over stroke the clutch and damage it.

[JerryBoone]

Thanks everyone. I've ordered a 7/8" slave cylinder. I'll let you know how it works out.

[Phil.C60]

It will also lower the biting point and make the action more progressive.....as long as you still get enough clutch clearance. I've found that pushrod length adjustment is quite fussy, needs to have no preload with everything at rest but only the slightest play clearance/play. Best done with the return spring disconnected. Hope this helps.

[prezoom]

Save the old one and have it sleeved. A spare is always handy.