Hydralic Clutch Ratios - Whats Corrrect?

[ChimpOnGas]

Can someone conclusively confirm the correct hydraulic clutch ratio for the TVR Chimaera please?

I currently run a 1" slave cylinder paired with an 0.70" master cylinder.

I know some have a different setup but my understanding is this may have been forced on them by their TVR repair/parts specialist due to the availability of parts (or more accurately lack of availability).

It's my belief I have the correct paired combination but I stand to be corrected.

Please confirm your current setup and what you understand to be the correct master & slave cylinder bore size combination.

I'm aware a smaller master cylinder bore paired with a larger slave cylinder will give a lighter pedal, but in such a setup the pedal will need to travel further to disengage the clutch which will likely make the system unusable.

I'm not trying to reinvent the wheel here as I'm very confident TVR did all the hydraulic ratio and stroke calculations a long time ago to ensure the perfect system.

All I'm trying to establish is what TVR settled on as that perfect slave to master cylinder relationship.

Its fair to say all our cars are getting on a bit, so it's very common for master cylinders and slave cylinders get replaced over time (often more than once), and sometimes with non standard parts.

This makes understanding the exact TVR chosen pairing harder to pin down, if anyone can conclusively confirm the real answer we would all be grateful if you can share your knowledge.

Thanks, Dave.

[ChimpOnGas]

So nobody knows the true answer then?

Or perhaps it's a secret?

[ChimpOnGas]

Ozstyle said:

Hi,
I have a late 94 Griffith 500 with about 40k on the clock, 1 inch slave and 0.7 inch master bores and by the condition have no reason to think they are not original items.
All my research indicated these are also the correct size. Master was weeping and replaced seals with a repair kit, slave was ok but removed to clean and check. I used to have difficulty engaging 1st gear at times when hot, found the slave to be a bit gunked up, since the clean and bleed no more issues.

Master cylinder - Girling 0.70 cast markings, 7/16 inch union thread. Pipe 1/4 inch diameter. The 7/16 union is larger than the standard Girling union size (TVR specific?)
Slave cylinder - AP Lockheed 99366 Q437 cast markings, union 12mm thread, bleed nipple 10mm thread.

I have been unable to find a Land Rover slave with 1 inch bore and 12mm union thread.

Oz

Excellent Oz, a quality answer and confirms my own belief the master cylinder is a 0.70" bore and the slave is 1".

It seems I have the correct combination on my car too, both are relatively new units, the master cylinder was changed some 4 years ago and the slave is only two years old.

I was interested to hear you where having gear engagement issues when hot as I also suffer the same. It's my belief the fluid is getting excessively hot after a sustained period of driving, I find the problem only raises it's head after two to three hours of driving when everything under the bonnet can become heat soaked.

Doe's anyone else have the same issue of poor gear engagement when hot?

[ChimpOnGas]

Sardonicus said:

our right it dont unless you displace all the old knackered fluid by 1st pushing the push-rod back into the slave with the bleed nipple open

I noticed this too, I even made up a very very slightly longer clutch slave push rod which I've had success with before on other Brit stuff.

This made bleeding the system so much easier, all air was eliminated in just three strokes of the pedal

But then I left it in and went for a drive, worked great for 10 minutes then the clutch felt all wrong

Result?

One very bent push rod

Not a mod I'd recommend

So what is really going on with the fluid or cylinders when everything gets heat soaked to cause the poor gear engagement

Is it a fluid overheating thing, a tiny amount of air still in the system or something else at play like cylinder bore expansion

The fact is it the very very slight clutch drag when properly hot sure as hell happens on my car and causes a slightly stiff engagement of gears (especially the lower ones).

Like I say it only happens after everything is properly heat soaked, for the first hour or so from cold the box slices through the gears respectably. But drive for two hours or more and then get stuck in stop start traffic and you really notice it as you have to try a lot harder to push the lever into first and second.

I'm all to aware the TVR linkage is a contributor to some degree but I also feel there's more going on, I'm pretty sure I'm suffering very slight clutch drag and it's definitely on happening when things are getting proper hot.

To put it into perspective it's nowhere near the undrivable end of things you understand, its just a small annoyance really

But I sure as hell would love to eliminate it once and for all

Edited by ChimpOnGas on Thursday 15th October 14:46

[ChimpOnGas]

Sardonicus said:

More than likely clutch drag Dave when the clutch assy expands especially the drive plate what little clearance you had when disengaged all but disappears .... result drag or what we in the trade term laying up easily identified on conventional cars because reverse gear cruntches when you select but seeing the T5 does this anyway unless you stall the spinning dragging input shaft by selecting a forward gear before hand not so easy to diagnose, I also think the solid bronze input shaft pilot bush does nothing to help this situation of drag

Edited by Sardonicus on Thursday 15th October 14:58

Right so you agree I've got clutch drag then Simon, that's a good start.

And you think the driven plate might be expanding, must admit I hadn't considered that.

The Helix isn't really my friend TBH, the bite point is'nt where I want it either, not on the floor as such but a bit too near it.

My leg is a fraction to straight at bite point so my knee joint is at the wrong point of articulation to give full power on clutch take up. This makes clutch control trickier than it should be, and it's then that the additional weight of the Helix really tries it's best to work against you.

Can you tell I hate my Helix yet

Anyway as we know my lovely Helix is getting it's marching orders very soon and I'm confident some of the less desirable traits I've suffered with it will be a lot lot better with the Lloyd clutch.

But what of the infuriating heat soaked clutch drag syndrome?

Will I lose that, or will it remain to bug me for ever

I know I'm making a mountain out of a mole hill here, none of what I'm describing is anywhere near as bad as I'm making it sound as the car remains perfectly derivable even in the very worst cases of heat soaked clutch components.

I do know I'm being fussy!

But the bottom like is I want a perfect gear shift like I know a T5 can give, and want that matched to a lovely light progressive clutch with none of this slightly annoying heat soak drag and the sticky 1st & 2nd engagement issues.

If there are any more ideas to banish this condition once and for all, please dont hold back in sharing them