TR6 Are you happy with your TR6 clutch pedal play?

[TR3driver]

My Stag uses the same slave as a TR6. The spring won't push the piston through the boot, but without the boot, it will push it out of the slave eventually. I have to force the pushrod into the slave (compressing the spring) in order to insert the clevis pin.

This was a deliberate design change; to make the clutch self-adjusting. The spring takes up any wear in the clutch plate (and pushrod/clevis), eliminating the need for the adjustment found on earlier TRs.

 

[piman]

Hello Randall,

this is strange as the Triumph 2000\2500 saloons which use basically the same units do not have that spring. I do not see what can actually push the slave piston back up the slave cylinder to allow so much free play? Once the clutch is engaged there is no pressure left on the slave cylinder so why would it keep retracting?

Alec

 

[Guest]

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[piman]

Hello Stirkle,

the more you explain, the less I understand what your problem is.
You say there is 3\4" free play, but your clutch wouldn't disengage with such play as that is greater than the push rod travel. Yet you say "It works well"
Within certain limits the length of the push rod is irrelevant, once the hydraulics have adjusted to a different length. The point at which the clutch pushrod attaches to the actuating rod arm is a fixed point, the pedal at rest is a fixed point and the pushrod travel is a constant length. So how can altering the pushrod make any difference?

Alec

 

[TR3driver]

this is strange as the Triumph 2000\2500 saloons which use basically the same units do not have that spring.

That is strange, as Rimmers show the 2500 & 2.5PI as taking the exact same slave as the Stag, and their Stag page clearly shows the spring.<div class="ubbcode-block"><div class="ubbcode-header">Quote:] I do not see what can actually push the slave piston back up the slave cylinder to allow so much free play? Once the clutch is engaged there is no pressure left on the slave cylinder so why would it keep retracting?[/QUOTE]I believe it gets sucked back by the return spring inside the MC pulling a slight vacuum on the hydraulic fluid. Remember the valve into the reservoir does not open until the piston gets back to the very beginning of the stroke, so the system is sealed for most of the pedal movement. For the spring to take up the freeplay as it should, it has to actively push the slave piston out against seal resistance (and pull fluid from the reservoir).

3/4" does sound like excessive movement though; and frankly, looking at the supplied photo, I think there is something wrong inside the bellhousing, like a broken taper pin or mismatched components. When the clutch is engaged, the lever should be at a slight angle towards the slave, but that photo looks like it is at a slight angle away from the slave. But if the longer pushrod works, I sure wouldn't pull it apart to fix it.

I drove for several years myself with a broken taper pin, by fabricating a longer pushrod.

 

[piman]

Hello Randall,

one thing about Rimmers is that they supply parts that were never originally fitted, due, I suppose to lack of original parts as they become unavailable.

For all intents, the hydraulic fluid can be likened to a flexible solid link. Press the clutch to the floor, the fluid pushes the slave to the extent of the fluid travel (Triumph 2000 again, there are two bore sizes of slave 3\4" and 1" the latter giving a longer throw to the push rod).
Release the pedal and the clutch pushes the fluid back up the line, assisted by the master cylinder retracting due to the return spring. There is not a vacuum as such and once the pedal is back to the rest position fluid can't (shouldn't) continue to flow back so the slave piston is prevented from moving any further into the cylinder. (I did say earlier that there is no pressure there, there is head pressure from the reservoir)
I wonder if that spring was more an anti rattle or such by keeping the throw out bearing lightly touching the clutch plate?

Yes, the check of the push rod\actuating arm angle is a simple check. I do not understand if the clearance is there naturally or that is generated by pushing the push rod back into the cylinder? I think my point originally is that adjustable push rods are not normally needed and not worth spending money on.

Alec

 

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[TR3driver]

There is not a vacuum as such and once the pedal is back to the rest position fluid can't (shouldn't) continue to flow back so the slave piston is prevented from moving any further into the cylinder.

Alec, I think perhaps you misunderstood me. Consider the case where (for whatever reason), the system starts with the slave piston pushed fully home in the slave; leaving considerable freeplay between the TOB & PP fingers. In that case, both the MC and slave pistons will move some distance without resistance from the PP. If you then take your foot off the pedal, the spring inside the MC is the only thing that returns the MC piston to it's extended position, it gets no help from the PP. And when it does, it will pull a small vacuum on the fluid, returning the slave piston (nearly) to it's starting point as well.

As you say, it acts like a flexible link; and the length of that link can only change when the 'foot' valve in the MC is open.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] (I did say earlier that there is no pressure there, there is head pressure from the reservoir)[/QUOTE]True, but in my experience it's not enough to reliably overcome the friction of the seal in the slave cylinder. Otherwise the slave piston would extend when the clevis pin is removed, even without the spring. A very smooth-running slave might do that, but, for example, the slave on my TR3A (which has no spring) does not.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I wonder if that spring was more an anti rattle or such by keeping the throw out bearing lightly touching the clutch plate?[/QUOTE]That is another function of the spring. Since the TOB is supposed to touch the PP all the time, it needs to have enough pressure put on it to spin the bearing. Otherwise, the rubbing of the TOB against the fingers will cause excessive wear and in many cases a shrill noise. This is a common problem with the various "heavy duty" bearings being offered, as they take more force to turn than the original TOB did. The solution is to increase the force applied constantly to the bearing, which can be done by either using a stronger spring inside the slave, or adding an external spring (like the one that comes with the Gunst kit).

(Others have altered the design to eliminate the constant contact, similar to the TR2-4 clutch setup. Also a valid solution, but eliminates the "self-adjusting" feature.)
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I think my point originally is that adjustable push rods are not normally needed and not worth spending money on.[/QUOTE]That much I agree with. Assuming of course you have one of the later Triumphs that had the "self adjusting" system; TR2-4 (eg) need the adjustment.

BTW, I finally found my Triumph 2000 SPC; it also shows the spring inside the slave. Page 19, illustration L29, P/N 513762. Furthermore, the P/N shown for the slave assembly is the same as my early Stag SPC; 211060 and my early Stag definitely has the spring. (Darn nuisance when removing the gearbox, as the piston has to be restrained to avoid dumping fluid on the floor. The old, tired boot didn't have enough grip /bcforum/images/%%GRAEMLIN_URL%%/grin.gif )

 

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