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MG MGB Technical - Clutch Carbon Thrust or Roller Bearing?

Which is better to use in a new clutch installation? The original carbon thrust throwout bearing or a newer style roller throwout bearing? I drive a 69 MGB

From memory there is lots of negative feedback about roller bearings, but I don't understand why.

James
James

I definitely say use the correct carbon type. Foolishly I paid a lot of extra money for a roller item when the carbon item was included in the kit thinking I was doing the right thing by my car. After a couple of thousand miles it started wittering or squealing just as it was taking up or releasing the load. Then I started reading about people finding they had to fit a pull-off spring kit to prevent the bearing being in continual contact with the cover plate and wearing excessively. I spoke to my supplier and they professed no knowledge of problems with the bearing or a pull-off kit - but then like a certain lady of the night once said "They would say that, wouldn't they?".

It is a complete waste of money because do I really think that I'm going to leave that old release bearing in there when next I have to change the clutch? Of course not. And having been a driver for about 40 years and had clutches last 60k and 75k (still going) and not a habitual 'clutch rider' I don't expect to wear out a carbon bearing before the clutch needs replacing anyway.

Having said all that, a roller bearing is *standard* in the V8. Quite why I don't know, but I *would* use another in that, just not the roadster where carbon was the original fitment.
Paul Hunt 2

James,

the carbon bearing is a fine solution, in my MG's there has not been a failing within more than 30 years. During this time i had problems with the ball bearing type on my wifes' car two times, allways making it nacessary to change the whole clutch assy although the liners were still in very aceptable condition.

I only can agree to the recomandation given by Paul!

Ralph
Ralph

No problem with carbon, as long as it is to OEM spec.

I bought a midget thrust bearing from Moss and the dimensions were all wrong...for a Midget, that is!
Dave O'Neill

I, too, recieved a roler bearing in the kit I purchased several years ago. After hearing of early failures I installed the pull off kit. Since then I have experienced no problems. However, I would not use the roller bearing again knowing what I know now. From what I've read, the roller bearings are no longer being sold by the major MGB supliers. Ray
RAY

There is not anything inherently wrong with the roller bearing style throw-out unit, but there was a type used originally which did not hold up well. Going from memory I'd say the bad one was a straight roller unit while the upgrade was a tapered roller bearing. Straight roller units are still in circulation and it's entirely likely that this type has been used in the roller bearing kits for the MG as some of them are still available for Chevrolets. If so it makes perfect sense that their life would be short. There was an external difference that could be used to identify them, I'm thinking the better units had a radiused contact surface while the old ones were flat. Normally a pull-off spring is used, but with a HTOB seal retraction is enough to remove the load and allow the bearing to stop, but this would be lessened somewhat by the leverage of a clutch fork and might not work quite as well.

The problem with the straight rollers was that being used on a radial layout the ends would skid but again that's IIRC. It could have been barrel shaped rollers or even ball bearings. Tapered rollers are made for that type of use and have no skidding, whereas the others do.

Jim
Jim Blackwood

How well does the roller bearing in the original MGB GT V8 clutch work?
James

I have a V8. owned for 8years and never have any problems with the clutch bearing, Just a thought, could part of the B problem be because the bearing pushes against the flat thrust plate designed for the carbon and therefore skids a lot thereby causing the noises mentioned above. Jim34
j soutar

My V8 release bearing has been fine since I bought the car 12 years and 70k miles ago. The one slight problem I do occasionally have is clutch drag causing grinding into reverse and baulking into 1st and sometimes 2nd if I haven't used the car for a while. This is a known issue, apparently, although I don't know what is causing it. The cure is to drive it more!
Paul Hunt 2

This thread was discussed between 09/01/2007 and 11/01/2007

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