Inadequate clutch throw

[Jules TR6]

12 hours ago, BlueTR3A-5EKT said:

Yes you need free movement at the master cylinder 1 mm will do. So long as there is no force on the cylinder piston by the push rod/pedal.  If there is, the piston in the cylinder will not clear the internal ports, holding fluid pressure in the hydraulic circuit.   
The spring in the slave cylinder (if fitted) keeps the slave push rod extended    It has no action on the master cylinder if the piston clearance of the master cylinder is maintained    

Looking at the hole at the top of the clutch pedal (that attaches via the clevis pin to the pushrod), it is oval. Initially thought this must be due to wear, but on closer inspection it looks to have been machined oval from the factory… though not 100% sure. 

If all linkages and fluid are optimal, could this oval hole be the required gap triumph built in to ensure there is no constant pressure on the system? A given gap that can’t be adjusted away by the mechanic (unless they unwisely bush it).

[RogerH]

Your ova hole theory is cunning - I think far too cunning for TRiumph.

There is always significant warniong about getting the gap correct so I would suggest the hole should be round.

I have a 4A so not exactly expert on the TR6 - somebody will come up with the goods.

 

Roger

[Z320]

Hi,

I adjusted all play on the master OUT

- with a REAL pedals stop (not the mushroom headed push rod pulling on the master)

- and the play of the pushrod not only andjusted down to zero but with a preload on the piston

With this all worries about play of pins in holes are gone and that works very well on my TRAA.

Yes, the system needs "play", but IMO only one time on the slave (4 cylinders)

or the selfadjustment on the 6 cylinders is enough.

Ciao, Marco 

Edited August 15, 2025 by Z320

[stuart]

4 hours ago, Z320 said:

Hi,

I adjusted all play on the master OUT

- with a REAL pedals stop (not the mushroom headed push rod pulling on the master)

- and the play of the pushrod not only andjusted down to zero but with a preload on the piston

With this all worries about play of pins in holes are gone and that works very well on my TRAA.

Yes, the system needs "play", but IMO only one time on the slave (4 cylinders)

or the selfadjustment on the 6 cylinders is enough.

Ciao, Marco 

Only one possible problem would be if the clearance or lack of it in your case Marco was affected by heat, Ive known brake problems when all the play was removed at that point on the brake master.

Stuart.

[Z320]

Sorry Stuart,

I am talking about the clutch, not the brake.

 

Edited August 15, 2025 by Z320

[stuart]

23 minutes ago, Z320 said:

Sorry Stuart,

I am talking about the clutch, not the brake.

 

Yes I know but the cylinders work on the same principle. Inadequate clearance on the brake master means the fluid wont return sufficiently and with the heat build up can lock the brakes on. Probably wont matter too much on the clutch but may load the bearing a bit more. Obviously on your concentric actuation setup that may not matter.

Stuart. 

[Chilliman]

8 hours ago, Jules TR6 said:

Looking at the hole at the top of the clutch pedal (that attaches via the clevis pin to the pushrod), it is oval. Initially thought this must be due to wear, but on closer inspection it looks to have been machined oval from the factory… though not 100% sure. 

If all linkages and fluid are optimal, could this oval hole be the required gap triumph built in to ensure there is no constant pressure on the system? A given gap that can’t be adjusted away by the mechanic (unless they unwisely bush it).

I have had the pedals with everything from nice round holes to to completely exagerated slots. Anything which isn't round gets welded up solid & re-fdrilled.

[Z320]

5 hours ago, stuart said:

Yes I know but the cylinders work on the same principle. Inadequate clearance on the brake master means the fluid wont return sufficiently and with the heat build up can lock the brakes on. Probably wont matter too much on the clutch but may load the bearing a bit more. Obviously on your concentric actuation setup that may not matter.

Stuart. 

Stuart,

thank you for your worry, but it is really needless.

The play given by the locking valve is about 1.5 mm.

Give the adjustable 5/16 UNF push rod a 1/4 to max 1/2 turn preload, this is about 0.25 - 0.50 mm less play.

The locking valve will remain opened this way.

And for the unlikely case it is locked, this will slightly reduce the play on the slave cylinder and not effect the clutch at all.

Different than you guess a remaining locked valve will effect any concentric unit  direct and much MORE, because they works WITHOUT ANY play.

Please don’t turn physics upside down.

Guess how TR mates smile when they step on my clutch pedal.

Ciao, Marco

 

Edited August 15, 2025 by Z320
any concentric unit, ot only my concentric unit

[Jules TR6]

I quote how the car should be, 1969 'Motor' magazine road test of a new car tuned by Triumph for a good review...

'The gear changes on this car were notchy and obstructive, particularly into first and second when the oil was cold; several attempts were sometimes needed to engage first at rest. With firm deliberate movements, though, changes could be made quite smoothly, especially as the throttle movement seemed less floppy than on other Triumphs. The clutch gripped smoothly and well but was very heavy to push, 52 lb. being quite demanding in traffic.'

Part of the joy of the TR6 is the gearbox action and clutch feel. Gearbox needing positive movement, clutch needing a meant foot... this chimes in with the rest of the vehicle. Ok we might all want a super smooth gearbox and light clutch pedal in an ideal modern car, but the TR6 was never this, and I don't know if it's an upgrade to something that upsets the balance of what is a rudimentary direct raw drive - that we all miss today and why we enjoy the TR6. I actually do want quite a heavy clutch feel in this vehicle, and with all the bumps in country roads felt, this pressure is more controllable and smooth when re-engaging the clutch.

0.75" bore for me, and I shift through gears getting to that 0-60mph in 8.5secs, very pleasurable indeed - when I'm not doing the super gentle chauffeur drive - perfectly possible as well.

Edited August 15, 2025 by Jules TR6

[BlueTR3A-5EKT]

I agree with the statement ‘quite demanding in traffic’

Having just completed the 10 mile 4 lane car park in West London  AKA M25 at 4 pm today, from the A30 to the M40 in a TR with a lighter clutch than standard I am so pleased I have gone to a smaller master cylinder bore size for the clutch.  The clutch operation is so much more acceptable   Previously it was just uncomfortable after just 10 mins of stop start driving.   

[Jules TR6]

10 hours ago, BlueTR3A-5EKT said:

I agree with the statement ‘quite demanding in traffic’

Having just completed the 10 mile 4 lane car park in West London  AKA M25 at 4 pm today, from the A30 to the M40 in a TR with a lighter clutch than standard I am so pleased I have gone to a smaller master cylinder bore size for the clutch.  The clutch operation is so much more acceptable   Previously it was just uncomfortable after just 10 mins of stop start driving.   

I'll stick with the TR6, top down, bird calls passing, on country roads, full clutch felt, full power, exhaust note over little bridges.

Soft BMW for the M25 and then the harsh bits up to the M6 and M8, and beyond, easy.

That said, I might try a smaller bore next time, though will probably still stick to the back roads. 

Edited August 16, 2025 by Jules TR6

[Z320]

The hole clutch release mechanism of our TRs, also compared with other cars of this decades, is such a unbelievable poor construction!

IMO to glorify it must be a sadysm-, „real man“- or CDR-issue.

Looking on all this rubbish, the people „improve“ on TRs, the clutch is one of the most reasonable.

It is not only an issue of convenience, its also more safety and allows us to drive our loved cars longer.

Edited August 16, 2025 by Z320

[stuart]

2 hours ago, Z320 said:

The hole clutch release mechanism of our TRs, also compared with other cars of this decades, is such a unbelievable poor construction!

IMO to glorify it must be a sadysm-, „real man“- or CDR-issue.

Looking on all this rubbish, the people „improve“ on TRs, the clutch is one of the most reasonable.

It is not only an issue of convenience, its also more safety and allows us to drive our loved cars longer.

Its mainly a TR5/6 problem Marco, you`ll notice very few if any complaints from earlier TR owners.

Stuart.

[Z320]

Yes I know,

based on a not good construction / hydraulics

the Triumph guys developed it worse and worse with each next model.

“Best“ on the 6 cylinders LHD with B&B clutch cover „new design“

 

Edited August 16, 2025 by Z320

[harrytr5]

I have driven my TR5 many years and fitted a Tilton annular clutch mechanism when completely rebuilding it in 2003 and on the road 2004. I chose this system after a lot of research and bought the kit from Neil (Revington TR) Leycock new old stock cover and clutch plate. The tilton was a bit tricky to set up but has worked well over the years with a light feel. On Marco,s excellent advice I then changed my clutch master cylinder to a 5/8" bore to make it even lighter.

The modern *Cambridge Motorsports annular clutch kit is a delight to fit as the kit is designed for TR5/6 and all measurements are preset (I still measure though)

*We have around five running around with this kit and all are very happy.

I hate heavy clutches and no need for it.

My left leg is not as strong as it was and these kits are a blessing.

Regards Harry

[Magz]

I have now tried various combinations of 0.75" and 0.70" masters and standard and "long throw" slaves, and the winning combination for me was the 0.70" master with the long throw slave. Engages and disengages smoothly each time, no issues getting first from a cold start, runs through the gears are smooth. 

Long Throw Slave:

https://www.sportscarpartsltd.com/Clutch-Slave-Cyl-Long-Throw-TR6_p_655.html

[Z320]

Hi Mr. ?,

great to hear you are pleased with the smaller 0.7" master.

It has a smaller surface, this produces more pressure BUT pumps less fluid.

This makes the slave pistion travel 12,9% less = (1 - 0.7²/0.75²) x 100

Why ever a "long throw" slave makes sence on your TR6,

a smaller master cylinder does not need it.

Ciao, Marco

[Magz]

1 hour ago, Z320 said:

Hi Mr. ?,

great to hear you are pleased with the smaller 0.7" master.

It has a smaller surface, this produces more pressure BUT pumps less fluid.

This makes the slave pistion travel 12,9% less = (1 - 0.7²/0.75²) x 100

Why ever a "long throw" slave makes sence on your TR6,

a smaller master cylinder does not need it.

Ciao, Marco

My new-to-me TR6 came with a .70" master and a standard slave, but they leaked from sitting for a long period of time with the previous owner, so actuation suffered as air was entrained through the seals. A new .70" master with a new standard throw slave did not totally disengage the clutch, despite multiple attempts at bleeding including a pressure bleeder. A new .75" master with the standard slave also failed to completely disengage, but was slightly better than the previous combination. The new .70" master with a new long throw slave achieved perfect clutch actuation with a single pressure bleed.

Thus, my experience recommends this combination.

[Z320]

you repaired somthing different by accident without realising this,

btw the "warning" in the "description" of the master makes no sence 

[Magz]

2 hours ago, Z320 said:

Why ever a "long throw" slave makes sence on your TR6,

a smaller master cylinder does not need it.

Ciao, Marco

Going to the .75" master gave me 13% more piston travel than the .70" master, with the standard slave. That was an improvement but was still not enough to completely fix the disengagement issue. The long throw slave is advertised as having 30% more throw than standard, so going back to the .70" master and adding that long throw slave gave me 30% more throw than the .70"/standard slave combo, and 17% more throw than the .75" master/standard slave combo, and that solved the problem.

There's nothing more persuasive than success!

[Z320]

Interesting issues:

what is the piston diameter / bore of the „long throw“ slave, please?

what is your name, please?

Ciao, Marco

Edited November 20, 2025 by Z320

[Magz]

8 hours ago, Z320 said:

Interesting issues:

what is the piston diameter / bore of the „long throw“ slave, please?

what is your name, please?

Ciao, Marco

I do not know any specs on the long throw other than what is stated in the link I posted. I also don't intend to disassemble it to measure them. 😉

My name is Robert.

[Drewmotty]

I believe that the long throw cylinder is 7/8” bore. 

[Z320]

Hi Robert,

thank you to answer again, sleeping a night over it I‘m with Drewmotty (thank you, D.).

Original is 1“, only with a smaller piston more way of travel is possible,

sadly with a massive reduction of force.

If wanted I can show the calculation later,

apart from anybody else wants to show (I‘m not the only one with a pocket calculator).

Ciao, Marco

Edited November 21, 2025 by Z320

[BlueTR3A-5EKT]

On 11/20/2025 at 2:50 AM, Magz said:

I have now tried various combinations of 0.75" and 0.70" masters and standard and "long throw" slaves, and the winning combination for me was the 0.70" master with the long throw slave. Engages and disengages smoothly each time, no issues getting first from a cold start, runs through the gears are smooth. 

Long Throw Slave:

https://www.sportscarpartsltd.com/Clutch-Slave-Cyl-Long-Throw-TR6_p_655.html

?   Have you also renewed the clutch pedal shaft bearings, welded up and re drilled the clevis pin holes in the pedal, fitted new clevis pins, welded up and re drilled the master cylinder fork ends.  All to match the new clevis pins.   .?

 

Next test.   Under the car, disconnect the slave cylinder push rod from the lever.   Push by hand the lever as far rearwards as you can.   Now move the lever towards the engine gently and slowly.   When resistance is felt take note. Now push the lever a bit further and more firmly towards the engine.   Did you get a bit more movement of the lever?   Your clutch cross shaft pin has sheered.   
Fitting  longer throws and bore size changes will makes the slave push rod go further to enable clutch disengagement, but it comes at a price.   Heavier pedal pressure.is required and the cross shaft pin inside the bell housing remains broken.

Lots on here of how to double pin that fork to cross shaft, but the gearbox must be removed to do it.

Edited November 21, 2025 by BlueTR3A-5EKT