Clutch Woes - Seeking a solution

[stephen low]

Folks I'm chasing help please!!

I bled my clutch system some time ago and found that you had to be Hercules to be able to depress the clutch.

I've used a McLeod street pro clutch ie a slightly heavier OEM version of the standard clutch and went with an external hydraulic system with a 3/4" clutch master and I believe a standard pbr slave cylinder and fork as supplied through Dellows. I can't quote bore size on the slave at this time.

Revisiting the issue recently we first thought that it was slave misalignment affecting leverage on the fork and with test packing this did only fractionally reduce pressure.

Next it was discovered that there was interference as the Dellow bell housing hadn't provided sufficient clearance to the top of the fork.

I ground away the housing to provide free clearance and this too again slightly reduced the pressure and you now only have to be Hercules's sister to press the pedal. Just ask Doug Farquhar, he was the poor bloke holding the pedal down whilst I was doing the grinding around the fork lever.

So the next step is for me to try and determine how much pedal stroke will release the clutch and let the rear wheels turn, assuming this happens.

However I am keen for any and all feedback as to how to overcome these woes as the car would essentially be un-driveable with the clutch as currently working.

I'm trying to avoid having to pull the engine and gearbox out of the car, so all suggestions and advice would be appreciated.

Cheers and many thanks in advance of some hopefully good suggestions.

A frustrated Slo

[Zedn]

How does it feel with the bleed nipple open? Ie no blockage or binding.

[stephen low]

Zedn

I assume this is just then a test of the operation of the pedal or master cylinder correct?

Binding suggests what?

I actually had a manufacturing fault in the first master installed and bought a replacement only two months ago or thereabouts.

The buggered master simply ended up locking up and not returning the pedal because of a piece of swarf that eventually scored the bore and interfered with the plunger.

There was still a lot of pressure needed to push with that master.

Slo

[renovationinnov]

slowly
had a silmlar problem with a dellows kit
I found that you could slide the throw out bearing by hand easlier by when the clutch fork was attached it would bind on the input shaft
so I found I had I had to machine the input shaft 1thou for clearance that what dellows advised & it worked
hope this helps ...ps ring dellows & see I they have had this trouble before

good luck rob

[Zedn]

Originally Posted by stephen low

Zedn

I assume this is just then a test of the operation of the pedal or master cylinder correct?

Binding suggests what?

I actually had a manufacturing fault in the first master installed and bought a replacement only two months ago or thereabouts.

The buggered master simply ended up locking up and not returning the pedal because of a piece of swarf that eventually scored the bore and interfered with the plunger.

There was still a lot of pressure needed to push with that master.

Slo

Just to isolate any restrictions in the line or master cylinder.

[sambo]

Slowy, wouldn't you want to confirm correct master/slave combo for that setup before going much further?

[stephen low]

Thanks guys for the ideas.

And yes I do need to confirm the slave sizing that will happen.

Got an email the day after I contacted McLeod in the States and they suggested the 3/4" master as a correct size but that a 7/8" or 1" slave is needed.

I'll need to suss all this out.

Cheers

Slo

[iva bigan]

Slowly
Measure your pedal ratio ,it often gets compromised on kit cars,

Iva Bigan

[Magicalab]

Hi Try contacting Mal Wood Automotive - Home I got a set up from these guys and it works really good, good luck Mark.

[stephen low]

Mr Bigone I know the pedal ratio is fine as the previous set up with a T5 gearbox using a wire clutch operation worked a dream and with pedal pressure as I would have expected.

On advice from McLeods that the master sizing I have seems appropriate it seems clearly more likely that there is something amiss either with the slave sizing or in the operation somewhere related to fork and thrust bearing.

I clearly need to confirm the slave cylinder size and make a decision from there.

But cheers for the input anyway.

Not so Slowly

Slowy

[Aussie Mike]

So you are saying the cable clutch worked fine but the new hydraulic is too heavy. How can you be sure the pedal ratio is right when you had a cable clutch before?

Have you measured the pedal ratio? i.e distance from pivot to pedal tread and distance from pivot to pushrod attachment.

Have you had the car running to determine the clutch take up point?

Cheers

[CHANMADD]

in error

[CHANMADD]

How can you do any work untill you know the diameters of the master and slave.................
The correct hydraulics can make light work of even the heaviest clutch........

[stephen low]

Mike

I had previously measured the pedal ratio I recall and am comfortable with its length ratio either side of the pivot. That it worked well on a cable set up I'd have thought would be good proof too to validate that the pedal length isn't really a cause for concern.

Chanmadd

Yes as I said earlier knowing what the slave size is critical too and I will be getting to the car to check this out as the first step.

I do now suspect the slave may be undersized, at least that is my hope, but we will see.

Thanks again guys.

Slo

[sambo]

Undersized slaves are no good Slowy, you end up doing all the work yourself

[iva bigan]

Slowly

Who was it that said ? Convince a man against his will is of the same opinion still.

In all seriousness ,why don't you measure the pedal ratio properly so that you can eliminate that first,it cost nothing to do so where as m/c and s/cylinders all cost money and may not rectify your problem if the p/ratio is inadequate .

Good luck with your projects
Iva Bigan

[stephen low]

Thanks Iva

Who did say that?? lol

I will revisit the measurements, though I'm sure that's been done before, but you are right, in that doing this eliminates one issue.

Though as can be seen in the photo below from early in my first build stages, the pivot ratio and hence leverage into the clutch master is well in my favour. I don't believe this was altered during the current rebuild but I will check for completeness.



As a top pivot clutch pedal system what's the suggested ratio between distance above and below the clutch master connection point onto the clutch pedal?

So how big is your slave Paul???

Slo

[sambo]

I don't have a slave Slowy, just a master or should I say MISTRESS.

Watching this thread I'm glad I stuck with the factory setup.

[stephen low]

Paul your secret is safe with me from SWMBO - lol

As to set ups I had to turf the T5 as it was buggered but the TKO in itself should be fine.

However I've been less than happy with the Dellows bell housing I bought given the extra work that's been needed to make things work that should have simply happened.

In hindsight an internal hydraulic release system might have been the best outcome but it's probably too late for that.

So I'll struggle onwards to find the right fix but I sincerely hope its not the same issue as Rob has explained above on his Dellows kit!

[muzzza]

Clutch set-up will always come back to bite you if not done correctly.
Pedal travel.......pedal ratio........clutch fork ratio......clutch travel + clearance......and master / slave cylinder volumes.
A bit of simple geometry and you are all done .

One small point not mentioned so far has been cylinder pus-rod alignment. If master cylinder / slave cylinder push-rods are not within a few degrees of straight, compression force when you push in the clutch, forces the cylinder piston assembly sideways within the bore and the alloy cylinder will gall very quickly. Pedal pressure will go up dramatically and you may see a black residue start to form. ( alloy and oil......even swarf ? ) Precise measurements will fix everything. Good luck. Murray