Clutch Adjustment

[Chris Hubball]

Learned Gentlemen

I have converted my TR4 from a spring to a Lockheed Diaphragm clutch. My questions are do I delete the return spring on the slave cylinder if so why ? should I also retain the threaded adjusting rod and as per the manual set the clearance at .010 free play or fit a plain unthreaded rod if so from what or what length.

Cheers Chris

 

 

 

[peejay4A]

Your choice but when I did the same I set the clearance as per the book then did away with the return spring which renders the mechanism self adjusting (the clearance closes up on first operation) as in the 6 cylinder cars. 

You’ll get the opposing view which will cite wear on the release bearing as a reason for retaining the return spring. It works for me (and all the 5s and 6s out there).

[stuart]

I always stick with the adjustable rod and spring for all 4 cylinder cars.

Stuart.

[tim hunt]

To muddy the waters further Chris see the attached Leyland Triumph Bulletin of December 1966 advising an increase in clearance for the diaphragm type clutch from 0.100" (NOT 0.010) to 0.300" to "prevent overloading the thrust mechanism".

Tim

[Lebro]

1 hour ago, stuart said:

I always stick with the adjustable rod and spring for all 4 cylinder cars.

Stuart.

+1

[silverfox4]

does anyone have more background on the above bulletin as posted by Tim. I am having trouble wrapping my head around the -300" clearance = would it not make for a sloppy clutch?

Cheers,

Alf

[Geko]

3 hours ago, silverfox4 said:

does anyone have more background on the above bulletin as posted by Tim. I am having trouble wrapping my head around the -300" clearance = would it not make for a sloppy clutch?

Cheers,

Alf

I think the bulletin is a bit elliptic - the clearance increase is probably meant to compensate the fact that the spring has been deleted on the 4A. 

[Geko]

1 hour ago, Geko said:

I think the bulletin is a bit elliptic - the clearance increase is probably meant to compensate the fact that the spring has been deleted on the 4A. 

read "elliptical"....

[tim hunt]

I run the 0.300" clearance without return spring and don't find the action at all sloppy.

Tim

[ianc]

0.300" is nearly a third of an inch and strikes me as an enormous clearance, which would make disengagement of the clutch quite difficult.

On my TR4, I have a diaphragm clutch and spring, and, with the spring disconnected, I set the clearance to about 10 or 20 thousandths of an inch (0.010" to 0.020") just by feeling movement (years of experience).

I have also installed an adjustable operating rod between pedal and clutch master cylinder, so as to eliminate the lost motion at that that end - this means that the piston starts to move in the master cylinder almost as soon as I move the pedal.

Ian Cornish

[peejay4A]

My belief is this. It doesn’t matter what you set the clearance to (within reason) if you delete the return spring. The clearance will disappear on first operation of the clutch and the only clearance that will remain is that caused by the release bearing run out and retraction due to the rubber seals in the slave cylinder.  That’s how the mechanism is self adjusting without the return spring. I’ve run mine this way for 15k miles.  Here’s a question. If you leave the spring in place how often do you need to crawl underneath to check and/or adjust?

[stuart]

Just now, peejay4A said:

My belief is this. It doesn’t matter what you set the clearance to (within reason) if you delete the return spring. The clearance will disappear on first operation of the clutch and the only clearance that will remain is that caused by the release bearing run out and retraction due to the rubber seals in the slave cylinder.  That’s how the mechanism is self adjusting without the return spring. I’ve run mine this way for 15k miles.  Here’s a question. If you leave the spring in place how often do you need to crawl underneath to check and/or adjust?

Not so far in 25K but Im very sparing on my clutch.

Stuart.

[ChrisR-4A]

19 hours ago, stuart said:

I always stick with the adjustable rod and spring for all 4 cylinder cars.

Stuart.

+1, I’ve run mine like that for 22 years with no problems, what is also usefull is to have the adjustable pushrod on the master cylinder.

Chris

[Lebro]

Pete is spot on in the description of how it works.

Me, I have the spring, & have not had to adjust any thing in 5 years = approx 14000 miles

 

Bob.

[peejay4A]

Here’s a thought and my logic might be wrong but I’m pretty sure I’m not. As a diaphragm clutch driven plate wears the effect is to move the spring leaves towards the rear of the car thus closing up some of the clearance you set in an adjustable rod with the spring in place.  After a while the release bearing is in permanent spinning contact with the diaphragm spring but you won’t notice it because the clutch feel will be fine - unless you adjust the clearance to account for wear. How fast does it wear and how often should you check the clearance to avoid wearing the release bearing out?  

[silverfox4]

+1 on retaining the spring on the 4A, to avoid the TOB rotating continuously. On this basis I am not yet convinced that .300" does not provide for excess slop 

Alf

[peejay4A]

So why do the six cylinder cars have no return spring?  It’s the same clutch (assuming you’ve gone for a diaphragm conversion) to all intents and purposes. 

[silverfox4]

good point Pete, but I have no answer to the TR6 configuration. It's just Intuitively, the continuous rotation of the TOB seems wrong, and the spring helps against that..

Cheers,

Alf

[Waldi]

9 hours ago, peejay4A said:

Here’s a thought and my logic might be wrong but I’m pretty sure I’m not. As a diaphragm clutch driven plate wears the effect is to move the spring leaves towards the rear of the car thus closing up some of the clearance you set in an adjustable rod with the spring in place.  After a while the release bearing is in permanent spinning contact with the diaphragm spring but you won’t notice it because the clutch feel will be fine - unless you adjust the clearance to account for wear. How fast does it wear and how often should you check the clearance to avoid wearing the release bearing out?  

Hi Pete,

On my 6 there is a return spring in the slave cilinder and that should be there.

if the driven plate wears, the fingers on the diaphragm will move to the rear (good observation!) The piston in the slave will simply move a bit inward to compensate for this and the spring in the slave cil. will maintain the pre-load (which isn’t much by the way).

I’m not familiar with the earlier designs.

Regards,

Waldi

[peejay4A]

Thanks Waldi, that’s how I see it. Also anything to avoid crawling under the car,  to check that a clearance might have closed up, even though from others’ experience it doesn’t seem to. 

I think the clearance will close on the older design of clutch too. 

Edited October 17, 2018 by peejay4A

[stuart]

I suspect the change is also to do with the bean counters, fixed rod is cheaper..

Stuart.

[tim hunt]

Don't shoot the messenger. I am only drawing attention  to a Leyland Triumph advisory. Frankly I am no wiser on this return spring or no return spring business than I was 44 years ago although I do find the absence of this provision on the six cylinder cars illuminating. Ho Hum.

Tim

[Waldi]

Hi Tim,

I hope I was not shooting:)

the adjustable rod does make sence to me if you want to compensate for exessive accumulated wear in all pivot points. The adjustable rod can compensate for that, so your piston is back in tge slave cilinder where it should be.

 

For my understanding: Which return spring has been deleted on the tr6?

regards,

Waldi

[peejay4A]

It’s the big external spring that runs from the clutch operating lever to the slave cylinder mounting plate. 

Maybe they opened the clearance to 0.3 to extend the period between adjustments being required. For what reason is s mystery. Maybe driven plates were wearing too quickly. 

[Waldi]

Thanks Pete, 

now I understand, looked at the Moss site.

interestingly the old design (TR4A) was pulling the clutch “free”, while the later TR5/6 design is gently pushing the piston towards the clutch lever.

Waldi