Surflex Clutch Plate – Is there a problem?

This topic contains 6 replies, has 5 voices, and was last updated by james lucas 1 week, 5 days ago.

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November 15, 2019 at 10:06 pm #9383

james lucas
Participant

Sorry chaps – second attempt. Following the replacement of a new clutch on my T150v this year the operation has been, to say the least ,”heavy” to the extent that it has pulled the nipple off the cable. I went to Beezump this year and sampled enough clutch levers to realise that mine was definitely not right.

Following the article in the TE 242 page 59 by Clive Blake this prompted me to examine the clutch assembly. I took the clutch to Richard Darby who had kindly offered to examine it. Using the paper finger test the pressure was up to 40 thou with little sign of release of the fingers. The clutch was examined and it was found that the rivets on the Surflex clutch plate had been in touch with the fingers on the pressure plate. See photographs.

Richard examined other pressure plates in his possession and found that the fingers on the pressure plate has been machined to allow a recess. see photo. Was this a problem identified by Triumph?

Any comments or observations on why i have had this problem on my clutch would be appreciated. Thanks James
November 18, 2019 at 11:50 am #9417

Angus McLeod
Moderator

I don’t think Triumph would ever have fitted a clutch like that, but I could be wrong. I’ve only ever used the original type and never had a problem. I had one relined after 90,000 miles. I also sprinted a class winning bike with a standard plate without issue. It did have a stronger spring though.
November 18, 2019 at 8:58 pm #9428

Clive Blake
Participant

If you want to discuss, give me a call tomorrow evening on 07802965092.

Clive.
November 20, 2019 at 2:33 am #9432

David Patterson
Participant

Good information, thanks for posting.
I just put a Surflex plate in my clutch. It passed the paper test on the bench but I haven’t ridden the bike yet. I’ll report back if there’s any trouble.
November 20, 2019 at 5:55 pm #9437

nigel wheatley
Participant

The ‘problem’ is that it seems as if triples were fitted with 2 variations of the clutch pressure plate, although as far as i know the part number (57-3715) never changed. Clutch assemblies came already built up by AP in leamington who also made the very similar BMC Mini clutches so it’s possible that BSA/Triumph were unaware of the variation.

You can see the variation in the 2nd and 3rd photos that James has posted above. In the 3rd picture you can see a flat is machined in the each of the 4 webs that support the plate, the flat is about 11/16 or 18mm wide. In the 2nd picture the pressure plate has no machined flats. Both examples are original un-modified/standard clutch pressure plates

The ‘problem’ arises because the Surflex replacement clutch driven plate comes with rivets that stick out/proud when compared with the AP original. If you have a clutch pressure plate that is without the machined flats, then the rivets on the Surflex plate can catch and drag on the supporting webs of the pressure plate and that will create a clutch drag as it will impossible to seperate the two components cleanly. If you have the pressure plate with machined flats then there is no problem as the flats give enough clearance for the rivets on the Surflex plate

We must assume that when Surflex began making replacements, they were using a pressure plate that had machined flats and weren’t aware of any without the flats. The original and unavailable AP clutch plates came with rivets that were/are flatter/flush with the plate and which will clear the un-machined pressure plate in James’s 2nd picture.

So why did AP start supplying clutch pressure plates with flats machined in them? Who knows? but could it be linked to the developments in BMC Mini and the aftermarket in car parts if Mini clutches were being reconditioned with new friction material then there would presumably need to be more clearance for new rivets?
November 20, 2019 at 6:44 pm #9438

Clive Blake
Participant

I have in my workshop 5 late (Small Heath) T150V T160 clutches, although the pressure plates don’t have machined flats on them they all clear the rivets on a standard Surflex clutch plate, I do as a matter of course now machine 0.050″ from the rivets as they could contact the pressure plate webs when worn.
November 24, 2019 at 7:22 pm #9456

james lucas
Participant

This is an update on the problem solving the Surflex clutch plate . In my initial post you will note from photo 1 and photo 2 there is evidence of the rivets on the friction plate coming into contact with the webs on the pressure plate. thus preventing a separation between the two. I have had the webs machined to provide additional clearance and this overcame the problem between the rivets and the pressure plate. Equally I could ,as Clive Blake suggests, machined the rivets to provide the clearance which i may still do to ensure sufficient clearance at the friction surface wares down.

Having reassembled the complete clutch using the paper finger test i can now release the paper fingers at 23″ which must make an improvement to the clutch operation . It is worthy of mention that the placement of the pressure spring has to be placed in numerous locations to get the best clearance, it took me six attempts to find the best location but i feel it was worth it. Hopefully my patience will provide a lighter and a non dragging clutch. Thanks to those who have contributed to this post. James
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