Clutch Pedal Pressure

[ChrisR-4A]

The pressure needed to depress the clutch pedal on a 4 or in my case a 4A is considerably more than on modern, even high performance cars and although this does not normally present a problem it can if one has damaged ones left foot in some way.

Having looked at a few modern set ups the pedals look longer than a TR clutch pedal which has plenty of clearance between the end of the pedal and the floor so why not extend the pedal by about 50mm by welding a section in? Has anyone ever tried this? If possible this would be a simple fix to reduce pressure , some may say why not fit a servo but I already have one for the brakes and space is tight to fit another which only adds more complication and something else to go wrong.

[Graham Harris]

You could try a larger diameter slave cylinder, you will get less travel but if all is in good nick you should get away with it ok

Graham

[Fireman049]

I wonder what the combination of a longer pedal and bigger slave cylinder would be?

I've fitted my 3A with a 4A diaphragm clutch and the pedal is quite heavy to use.

 

Tom.

[Badfrog]

I have a very heavy pedal too, although the whole system is new/recent with upgraded disc and all.

I'm not that bothered by the heaviness, but what really bugs me is that the clutch comes in in one go. It's an on-off condition, no progressivity at all. Really nasty when you're close to an obstacle.

The master and slave cylinders are of the large bore type and the pipe is also large, more than twice the brake pipe.

No idea about what to do.

 

Badfrog, developping a "Terminator" left leg.

[Fireman049]

Hi Badfrog ~

 

I suspect that you have a faulty pressure plate or, perhaps, did you fit a competition pressure plate?

I once fitted a competition pressure plate to my Mini Cooper and it was a case of "in or out" and no half measures and it was extremely heavy. I soon changed it for a normal road clutch.

 

Regards ~

 

Tom.

Edited May 3, 2013 by Fireman049

[Graham Harris]

I'm not sure what size the piston is in the 4A slave cylinder but i think the standard size for the 3A is 7/8 inch. When i was rebuilding my 3A the clutch slave cylinder was sized and i couldn't get it apart so i ordered a new one from TRF. Now i didn't take it apart before fitting it but shortly after reasembly it started to leak fluid and i found the piston seal had been fitted badly and was half turned over in the bore. the end result was i got the original rebuilt and ordered a new seal from TRF and it was then i realised the the new slave cylinder from TRF had a 1 inch bore.The extra preasure required on the clutch pedal was verry noticable so if the master cylinder has a smaller diameter piston than the slave cylinder the clutch pedal will be easier to operate.

I think i would prefer to play with the hydraulics rather than start cutting and welding clutch pedals.

Just my two bobs worth

Graham.

[ChrisR-4A]

Thanks for input guys. I too was sold a 1 ins slave cyl a few years ago and got over it by using the lower hole on the cross shaft lever for 3 years. It did make the clutch a bit lighter but when I had the engine rebuilt I replaced the slave cyl and that's when I found it was the wrong size.

My thoughts with lengthening the pedal was that it would not compromise the travel of the cross shaft and there should be a few old pedals around as they don't usually wear out except for the top pivot hole which is an easy fix.

Also I was going to replace the bushes on the pedal shaft later this year so pedals are coming out anyway.

[graeme]

I have heard that the co-axial clutch release kit makes the pedal much softer and controllable like a modern. I have not used one, but would be interested to hear from anyone who has one fitted.

 

Cheers

 

Graeme

[AndrewMAshton]

Hello, I have fitted the co-axial clutch and it is a lot easier with more control, I found the cross shaft quite severe although that could have been my bad driving, I got mine from racetorations, lovely piece of kit but no instructions, I muddled through in the end though, there is a thread on the advantages and disadvantages of bore size of master and slave cylinder and the effect of 1/4" v 3/16" bore pipework, something to do with pedal travel. All in all a worthwhile but expensive mod, also do you know if you have the 4 or 4A clutch, the 4 has three fingers and the 4A has a load of them, the 4 requires more effort, Cheers, Andrew

Edited May 3, 2013 by AndrewMAshton

[Fireman049]

When I converted my 3A to a (4A) diaphragm clutch I was very lucky in getting a genuine Laycock pressure plate from TR Bitz.

(I have also got a spare one in my garage). These pressure plates give excellent clutch control.

 

Tom.

[Badfrog]

You're right Fireman, I have a rallye/competition type Borg and Beck I was convinced to buy when I changed the system a few years ago. That certainly explains my problem.

I must say that when Chris59 rebuilt the rear main bearing, he could observe the dismantled clutch mechanism to be like new. Visibly so "oversized" it didn't bother about my driving.

 

Badfrog

Edited May 4, 2013 by Badfrog

[BlueTR3A-5EKT]

How about first moving the slave push rod Clevis pin to the lowest hole in the clutch lever.

If not consider using a late TR6 clutch master cyl with a 0.700" bore rather than the standard 0.750". It certainly lightened the TR6 clutch pedal but but caused disengagement issues. Ie lack of.......

 

Cheers

Peter W

[dingle]

There is a good discussion on the Buckeye site (reliable clutch) concerning release pressures of different brands. Sachs was the lightest and LUK was the heaviest. The articles concerned the diaphragm clutches that were used on TR6s and are the same as the TR4a.

Berry

[ianc]

TRs require the clutch pedal to be pushed right to the floor to completely disengage the clutch and so avoid crunching the gears; being short in the leg, I have always found this to be a problem.

However, this can be ameliorated by removing the 'dead' movement before the piston in the master cylinder closes the port and starts pushing fluid to the slave cylinder - this requires a longer or an adjustable push rod. I have fitted an adjustable rod, supplied by someone in deepest Somerset, and now the piston hits the end of its travel about 1.25" before the pedal hits the floor, so I have attached a wooden block to the bulkhead so that I don't ram the master cylinder piston against end of its cylinder.

 

If one increases the diameter of the SLAVE cylinder, the amount of travel required at the MASTER cylinder will be increased in proportion to the square of the slave diameter divided by the square of the master diameter, and the force required will be reduced by the reciprocal of this.

 

Having had it in use for 20 years, I can recommend the TR6, diaphragm clutch as a method of reducing the loading of one's old left leg!

 

Ian Cornish