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MG MGB Technical - Clutch Release Bearings

A friend and I are both suffering from the carbon clutch release bearings on our MGB GTs that are used for historic road rallying wearing out after just 3,000 miles. We had heard that a roller bearing was available but suppliers like Moss and MGMotorsport report that thye no longer supply them as they are unreliable. We then heard that a Rover V8 bearing could be modified to fit.

Does anyone have any experience of this or have any alternative solutions to offer?
Graham Gilmore

Graham

Check out the MGA Thread: Clutch throwout bearings.

Moss does show a roller bearing but it is NA. Check the archives for sources.

HTH

Larry
Larry Hallanger

Ha! When I replaced my roadster clutch about a dozen years ago I splashed out a considerable additional amount of money for a roller bearing, only for it to start squeaking a few miles later just as it was taking up the pressure of the clutch. Then I started reading about pull-off springs to prevent excessive wear of this bearing, which is continually rotating when the clutch is released. Needless to say my supplier had never heard of such a spring, nor claimed to know of any problems with their bearings. *Then* I thought forward to the next clutch change, some 30, 40, 50 or whatever k in the future. Would I really leave that old roller bearing in there? Of course not! And do carbon bearings fail before the clutch needs replacement anyway? Not if you use the clutch properly they don't. So it ended up a complete waste of money and I would never buy another one.

However, subsequently I bought a V8, which is equipped with a roller bearing as standard, which has so far done 75k in my ownership on the original (to me) clutch. I will certainly replace *that* with the proper roller bearing when the time comes.

Whilst I can accept that competition puts a greater stain on everything I'm surprised they are failing after as little as 3k. If it were only one then I'd say it was how you are using it or some other problem, but with two doing it ...

Have you considered driving like the rally drivers of the 70s and 80s? I well remember one piece of film of a special stage where one of the flying Finns had a camera pointing at his feet the whole time, and apart from the start never used the clutch pedal, he just banged it from gear to gear. When asked why he drove that way he replied "It's not my gearbox".

Paul Hunt 2

Paul, thanks for the input.

The film is called the Flying Fins and is Timo Makinnen driving a works Cooper S - best film ever made!! Unfortunately the gear changes are not the problem. We do around 10 to 15 racing type starts for each event plus a lot of stops/start, clutch slips during a driving test on historic events. Hence the high rate of wear I think.

I hear that the latest clutch kits from Rover have a better quality bearing than the Borg & Beck ones which we have been using so far. I have spoken to Bill Price who was in the BMC Competitions department and he reports that their race MGBs used standard carbon bearings. However they were long distance races with few starts and relatively few gear changes.

What we really need to locate is some NOS BMC bearings!!
Graham Gilmore

I was under the impression that B&B *were* the better quality parts, as opposed to QH. I can imagine that 'driving tests' put a lot more strain and wear on than even stage rallying.
Paul Hunt 2

I do similar events to Graham who started this thread. I have just had a look at my roller bearing which has done 15,000 miles and it is running a bit rough and has no grease in it.

I think will fit a carbon one this time. You can get a 'standard' one or, for three times the price, a Borg and Beck one.

I am more than happy to pay the premium for a better one. Any views or experience of the best one to fit that are currently available. I think there were some suspect ones a few year ago?

Mike
Mike Dixon

Personally, I would be hunting for new old stock.

I have a habit of just buying stuff from ebay...just in case.

When I was refitting my engine & gearbox after restoring the underside of the car, I re-used the bearing and pressure plate, as they looked to have plenty of life in them. I only replaced the friction plate as the springs were rattling.
Dave O'Neill 2

Check the alignment of the release bearing to the first-motion shaft. It's been said that they are all 'off' to a certain extent and the graphite bearing is designed to cope with that, more so than the so-called 'roller' bearing (from what I can see it contain ball bearings) which is designed to run concentrically on a guide tube as per the V8 and midget 1500.

Mine was off by a mile as above and probably contributed to the failure of a graphite and a 'roller' bearing in the 60k of my ownership, with the roller frequently squeaking and wittering for most of its life. The 'roller' didn't actually fail like graphite do where you end up with no clutch but when the noises got worse and the fluid level started dropping noticeably I changed it anyway - for a graphite that came with the clutch kit. As well as the damage to the bearing it had worn half-way through the release ring on the cover plate, offset to one side.

I ground down one side of the release arm at the pivot point and fitted a washer to the other side to move the whole arm laterally to centre the bearing on the shaft. That did offset the push-rod end from the slave cylinder a bit, so I ovalled one of the holes in the slave to correct most of that, considering that replacement of the slave cylinder is a lot easier than replacement of the release bearing. Coming up to nine years now and so far so good.

There were a spate of very premature failures of graphite bearings a few years ago where the graphite ring had been pinned in the casting instead of bonded, hopefully long gone now.






paulh4

I had a Moss one fitted - roller but carbon faced. A picture of it is attached as it came out last week and an image of new one for comparison

The carbon face is fine, but the bearings were just a little rough - certainly no noise audible. In some ways I am tempted with roller - when they fail you do tend to get some warning, as Paul alludes to, allowing you to limp home? When carbon ones fail they tend to be all or nothing?

The carbon faced roller one might be a good compromise? We do give it some 'hammer' on these events, with loads of standing starts when you include stop boxes, code boards and passage controls on tests and it has not done too badly?

There is an HRCR rally event at Gaydon on Saturday, I will do some asking around, MGBs are very well represented.

I will have a look at the alignment, looking at the wear it is probably OK? It is a bit out of my comfort zone to fix if it is not....






Mike Dixon

My graphite gave me some warning for a while - with the pedal fully depressed there was some noise and vibration so I didn't push it all the way down! On a Kimber Run at Chatsworth I felt it was getting a bit worse so on the run home decided I wouldn't use the clutch unless I really had to and got all the way home to Solihull in 4th and OD 4th - nearly 70 miles through towns, villages, roundabouts, junctions and traffic lights and I didn't have to stop once. That was 30 years ago, no chance of doing that now.

Backed it into the garage without using the clutch starting it in gear and stalling it, then two full presses of the clutch pedal, there was a bang and the pedal went to the floor - casting worn enough to break.
paulh4

This thread was discussed between 19/10/2006 and 09/01/2025

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