clutch biting point
Turbo Mini Forums

I'd agree with that, shoe choice can be critical, gayboy loafers are definatly out.... I did find my knee would ache after a stinty in traffic, but that may be more down to my knees...

Mine was a bit touch and go release wise for the first day or two, but it seemed to bed in and the bite point come up the pedal a bit, afeter a while i put on the metro longer arm, which moved the bite down again. maybe i wouldnt have got away with that from the outset.
I assume the settling is mostly from the 2 springs bedding in against each other

The key, as TD says, is the MASTER cylinder pushrod.
There is a lot of spare travel (before the porting stops working) in the master cylinder that can be used to increase the travel of the slave cylinder which also has plenty of spare provided its pushrod is set so that the piston starts from almost fully retracted.
I did all the measurements two years ago on a spare pedalbox and master/slave combination and you can get about 25% more provided you are happy with the clutch pedal being higher off the floor than the brake - which it is on many modern cars anyway.
The standard (master) pushrods do vary, I found the one of a green tag brake cylinder was the longest, but still not long enough.
However, these,
https://www.competitionsupplies.com/braking...linder-pushrods
are. The Tilton end is the same as Lockheed so a perfect fit.
You can't use them with their own adjustable end fork as it is physically longer (taller) so fouls the bottom of the master cylinder bore before full travel but I just cut one to length and welded it to a normal Mini fork end.
My reasoning was to actually be able to maintain the standard Verto release bearing travel but with an extended operating arm. If you just extend the arm (or use the Metro one) you fundamentally lose release bearing travel for getting the lighter pedal - increasing the pedal travel gets it back again.
Mines still not in the car yet (waiting till the engine's next out to replace the pre-verto grey with the RTS) but Graham T did the same mod (we bought the parts at the same time) and I've felt his clutch since and it's lighter than a grey.

EDIT - typo

Edited by Rod S on 18th Jun, 2018.

Schrödinger's cat - so which one am I ???

Edited by TurboDave16V on 18th Jun, 2018.

Thanks for the pointers guys.

I'll change the slave, arm and pins anyway but will have a look at lengthening the master cylinder pushrod as well.

It's odd about the twin springs causing these issues. Trying to get a handle on the reasoning. My guess is that although the two cones act as one in compression, the diaphragm fingers don't work together and flex a lot under compression.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

"work" is work if you measure it in Joules to change the spring(s) from their least loaded case (clutch engaged) to their highest loaded state (clutch dis-engaged by your foot) but it's still force X distance for the load and it's the force on your left foot we want to reduce.
Graham has the longer operating arm (as well as the master cylinder rod) and 25% increase there (5/4) equals 4/5 pressure on the pedal.
Re. the springs, IIRC yes, people have said they are all different, esp. the Valeo attempts which were mostly poor.
The finger part of the springs undoubtedly won't work well together as they have to minutely slide over each other.
That's why my - yet to be tested - setup has a 0.5mm sheet of PTFE between them, as I mentioned in a previous thread.
It is yet to be seen whether it,
(1) works the magic I'm hoping for,
(2) turns into a gooey molten mess and stops everything working, or,
(3) turns into PTFE dust which coats itself on the driven plate and makes it slip even more than from the usual primary gear oil seal leak....

Schrödinger's cat - so which one am I ???

When will you get it in Rod?

Here's a thought.

Are there different clutch pedals, just like there are different brake pedals? One used on the early pre verto and another used on Verto? It sounds like it only needs to be very subtle?........

Again, I cannot compare tho these issues, as my RTS with 2x 998 springs and standard MPi flywheel, using the original pedal that 1995 car came with, its great in every respect. There does seem to be a wide spectrum with the RTS clutches.

I just measured my plunger travel: 7.48mm
Clearly 1mm more than Sprox quoted on previous page, but it was (is) clearly needed.
Again, we’re seeing lots of variation!

Here is the information I gather back when I extended my master cylinder push rod.


Before I extended the Master cylinder push rod and release arm, I measured a movement of 4.85mm for the release bearing shaft.
Also:
Pedal height fully up, top face, centre of pedal to floor 130mm
Pedal height from floor, fully depressed 50mm
Pedal travel 80mm
Slave cylinder travel 12mm


This was with the RTS clutch in and operable. The only reason I was looking to change it was because the clutch was very heavy and “she who must be obeyed” could not actually push the peddle down at all.


From Rod’s earlier link we bought the 74-400, (74 series) which is 4” long.

From all my notes, it looks like I managed to get ~28mm of movement for the Master cylinder before the bottom of the clevis pin fork was touching the bottom of the bulkhead box.
Linear travel ratio from 0.750” bore master cylinder to 0.875” bore Slave cylinder = 1.3611:1

So I ended up with this

Pedal at rest (fully up) 160mm
Pedal Pushed down 44mm
Pedal travel 116mm
Master Cylinder movement 27.9mm
Slave Cylinder Movement 20.5mm

I had to remove the carpet underlay to get the clutch peddle closer to the floor, and I still have a limitation of the steering rack u-bolt stopping it from pushing further down, plus of course the thickness of the carpet.

The slave cylinder to release bearing arms I have, I measured as:

Verto type

upper length 58mm centres
Lower Length 28mm centre to ball centre
Ratio 2.071428571:1


Metro cable type
upper length 84.5mm centres
Lower Length 28mm centre to ball centre
Ratio 3.017857:1


Using a safe margin of 5.75mm max required travel for the release bearing shaft, giving me a large margin of error from my measured 4.85mm of travel. That gave me a ratio of 3.5:1 for extending the upper part of the slave cylinder to release bearing arm.
So giving me 98mm length for the upper arm, leaving the low arm section at 28mm

I had to mess around with the slave cylinder mounting a little, but ultimately it’s been working fine since I did it in March 2016, and the Missus can actually depress the peddle fully now…

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675

Wow, so I needed 7.48mm plunger travel to your 4.85mm.
That’s a huge 54% increase.
This variation is crazy.

Schrödinger's cat - so which one am I ???

I'm getting close on 8mm plunger travel. I can't get it in gear with the engine running but I can spin the engine with the starter whilst in gear and clutch depressed, so it's nearly there.

The parts I used:


Probably knackered springs :(

Edited by Paul S on 19th Jun, 2018.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

OK, let's throw another one into the mix....

How wavy are your wavy spring bits in between the two friction surfaces ???

I'm sure we've discussed this before but they all vary and I think I even posted photos of mine some time back.

The 190mm performance plate (un-available back in 2016 for quite some time) doesn't need much to clamp it up. Some standard plates I've seen need a lot more, hence a lot more plunger travel to release.

Graham and I both have the same 190mm plate because we bought the last few available at the time.

EDIT - and let's throw a few more variables in......

How many people drill out the rivets and tap M8 compared to using bolts/Allen screws/nuts, I've seen so many variations on the main steel plate. How many alter the rivets on the drive straps to either bolts or to add extra drive straps, how many alter the recesses where the outer bolts go, and so the list goes on.
The pair of springs may be the main difference in terms of release force but it's certainly not the only difference on how people have built these things since Robert's initial idea.

Edited by Rod S on 19th Jun, 2018.

Schrödinger's cat - so which one am I ???

Edited by TurboDave16V on 19th Jun, 2018.

Here's the first one I built for the 1293 with 2 No. 1275 springs:


The spring is pretty flat on that one.

That just worked straight off without issue.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Yep, that is flat for sure! It’s also the Valeo clutch.

I can’t find the message thread I made on the data from my twin spring and single spring clutch, but I was chasing max clamp force and set my clutch up initially to be flat with the AP friction disc. And it wouldn’t release. I’ve now sacrificed peak clamp by .75mm, and it will release.

Maybe if I’d have put twice as many shims in there I’d not have even had the pedal issue?

Way way way too many variables in all this confusion. If we were getting paid to do this, we’d just do a DOE and figure it out, but I’m not doing that crap on my time LOL

I think that the major variables are the springs thickness, initial compression and overall condition and the thickness of the driven plate.

I've only bought 2 clutch plates in the last 10 years and they are both the AP Racing Road Rally Plate - 180mm - C-AHT596, so I must be using one of them in my case.

EDIT: The 1293 twin spring Valeo was fitted with a sintered paddle plate, not the AP.

Edited by Paul S on 20th Jun, 2018.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I think what we really need is a replacement single spring to transplant into the verto, or preferably coming prebuild into a nice pressure plate assy ...

from memory guys the longer plunger and new clevis pins ( pedal box and wok) sorted it out for me

Yes i moved to the darkside

Instagram @jdm_brett

A year on and I've finally found time to try and fix this clutch.

Looks like I made a few mistakes on the build, firstly I used a pre-vert slave that I had floating about and secondly did not check the condition of the plunger arm which was well worn. So got myself a new slave and arm.


Also about 20mm of carpet and sound deadening under the pedal was not helping.

Took the master out and took some measurements. Looks like I can add up to 6mm to the length of the spindle which will raise the pedal from 120mm off the carper to around 140mm.


Bought an extended rod for a Tilton master. Thanks Rod S for the link above. Cut and welded the clevis end on to the new rod.


I now have about 8.5mm of plunger travel so hopeful of success. Just need to charge the battery and get some fuel to test it out

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Schrödinger's cat - so which one am I ???

Bugger, still no gears :(

However, I have managed to identify the problem.

Because I've cut of the starter nose from the Wok for the intercooler pipework, i can actually see what is happening at the clutch. Pity I did not check out what was happening when the problem first happened.

So, I can see the springs backing of the pressure plate by 3-4mm but the pressure plate is barely moving away from the driven plate.

Looks like the shouldered screws used to fit the clutch are just a tad too long to allow the pressure plate to back off enough to disengage.

I remember checking this out as something similar happened on the 1293. FOOK.

Now I've got to remove turbo, intercooler and manifolds to get the wok off. Updated coming in 2020 :(

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Sorted.

Just my incompetence in building clutches in the end.

Plenty of disengagement with normal 1/4" plunger travel. Add that to the puzzle :)

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Schrödinger's cat - so which one am I ???