Lotus Elan

Stiff clutch pedal

PostPost by: JerryBoone » Mon May 13, 2024 1:29 am

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.
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PostPost by: elans3 » Mon May 13, 2024 7:22 am

Smaller slave cylinder required by the sound of it !
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PostPost by: gjz30075 » Mon May 13, 2024 9:10 am

I'm pretty sure the slave should be 7/8".
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PostPost by: alan.barker » Mon May 13, 2024 10:31 am

The Slave should be 7/8" Dia
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PostPost by: Lotus54 » Mon May 13, 2024 1:05 pm

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.
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PostPost by: alan.barker » Mon May 13, 2024 3:33 pm

Lotus54 wrote: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.
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PostPost by: Lotus54 » Mon May 13, 2024 3:51 pm

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.

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PostPost by: alan.barker » Mon May 13, 2024 4:07 pm

Ok,
For sure the 7/8" dia Slaves are more expensive than the 3/4" dia
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PostPost by: Phil.C60 » Mon May 13, 2024 6:44 pm

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.
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PostPost by: 2cams70 » Tue May 14, 2024 8:21 am

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.
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PostPost by: JerryBoone » Tue May 14, 2024 1:38 pm

Thanks everyone. I've ordered a 7/8" slave cylinder. I'll let you know how it works out.
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PostPost by: Phil.C60 » Tue May 14, 2024 3:19 pm

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.
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PostPost by: prezoom » Tue May 14, 2024 6:12 pm

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