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MG Midget and Sprite Technical - carbon throw out bearing
|Is this type really all that bad? I keep my foot off the clutch at stop lights. Which one,-the carbon one or the upgrade ballbearing type lasts longer ? Bob C|
|Ball bearings lasts way longer, and carbon could wear faster if the fork bushing is gone.|
|Alex G Matla|
|My first one (carbon) did 80K or so miles before replacement due to worn clutch...|
|Have run my Frog for 40 years on a carbon thrust. Keep my foot on clutch at lights. No problems.|
|either kind can fail|
there has been talk (I checked the archives) of folks with the ball bearing type that have also failed (and plenty of posts, with photos, of folks with carbon type that have also failed). According to what I read here, those were an "early type bearing with resin cage" that folks had issues with. Based on that information, presumably, the current ball bearing ones are maybe better.
I just bought a Peter May bearing for mine, but haven't fitted it yet, so I've been watching this issue closely, and so far, the split seems to be even (my old carbon one also looks to be in fine condition, after 15k miles).
Maybe this is another one of those topics that depends on other factors that are not well known, so that some cars never have a problem with the OE Carbon, and some do, and why some of the modern bearing types last and some don't.
|both have their disatvantages|
the ball bearing kind tends to be nose heavy and tilt to hit the imputshaft.
And some have locked up for reasons unknown to me.
For the carbon one everything needs to be perfect.
The fork and pivot need to be perfect otherwise the carbon can hit the imputshaft and disintergrate.
both can work fine
|Some of the modern carbon bearings are badly made. If you can find a NOS carbon bearing, buy it.|
|Dave O'Neill 2|
|Carbon bearings will last as long as the clutch if one puts the transmission in neutral whenever sitting at a light, which is safer than keeping the clutch depressed (if a car behind hits your car, it is quite possible for the foot to slip off the clutch, driving the car forward). Cheers - Dave|
|The problemaitic new carbon bearings are those made with a small roll pin to key the carbon to the housing, (rather than have sufficient interferance I presume).|
These break up within 10K miles, usually less.
Don't ever accept one. The pin is only2mm or so, in from the side.
We have had two ball race ones fail, I think it is the nodding effet. Also, I suspect they are even more susceptible to wear in the pivot bush as they don't slide as readily across the release ring on the diaphragm.
The carbon bearings usually last the life of the rest of the clutch unless maltreated.
Interstingly, about 9 years ago ballrace bearings for the B were withdrawn from sale by at least one major supplier for quite a while due to problems.
|Another problem with the carbon bearings is that they are not made to the correct dimensions.|
|Dave O'Neill 2|
|Just had mine fail on a 1972 RWA midget - No mechanical noise at all until unable to get a gear - The carbon ring has completely worn away with most of the pressed metal carrier - Fitted 5 years ago manufactured by Delphi/Borg & Beck and disappointed that it has only completed approx 12,000 miles - Fortunately had just returned from a 1,500 mile tour around Northern Spain - Picture attached
|John M Platt|
|I can't recall about the Midget, but certainly some of the MGB Delphi kits we had through had the pin in the release bearing. Something to do with an Indian connection/subsidiary at the time, can't remember the details. It was a nigtmare for us, paid out on quite a few claims - a tidy sum including labour. |
So I can't over-emphasis the need to make sure you don't have one with the pin! But when sides of the bearing casing have have disappeared or it has completely broken up it's a bit difficult to tell if there was one.
|The replacement carbon bearings seem to vary enormously in quality. Mine failed after 4000 miles; its replacement is still going (another 6000) and makes the occasional 'graunch' when changing gear. The original (good old BL) managed to last 83,000 and was replaced as a matter of course when the engine was out being overhauled...|
Have also bought a PM ball bearing type just in case, in the meantime I never sit with the clutch depressed, always put it in neutral. Photo shows the same damage as John's.
|Just wondering if the type of pressure plate affects the carbon type as people with later cars (diaphragm spring) look as though they may have more problems than the older cars with coil springs. If my memory is correct I think many manufacturers changed to ball type bearings around the time diaphragms came in and I seem to remember it being said that this was because the bearing remained in contact with the plate all the time, but may be wrong.|
|had a simulair failure but mine fused with the table and tore that off the fingers.... well most likely my fault i had to keep driving home right ;)|
fitted a new one and it is working fine after about 10k KM
never keep the clutch pressed when not needed
|1275's had diaphragm springs and carbon bearings from the word go, and no problems - they generally lasted for the life of the rest of the clutch. MGB's and MGC's ditto.|
The real problem is some crappy examples on the market. Although if the pushrod is extended when it does not need doing, it doesn't help. As the clutch plate wears and the diaphragm release ring moves back in response, the bearing and fork also get pushed back. And of course so does the pushrod, into the cylinder. If the pushrod is too long then it will cause the piston to bottom out and so the bearing is in permanent under-load contact with the release ring thereafter. Premature failure of the bearing follows soon after.
|Do all these clutch kits ultimately come from the same manufacturer and if not which make would be the best available ?|
|John M Platt|
|The original AP/Borg & Beck/Delphi unit has always been much better in my experience ... until they went with dodgy release bearings (as above). I think they are over that now though, but any that you get it would pay to check that the bearing hasn't that nasty little pin.|
|The replacement is now fitted and the car is going well - Can anyone tell from my earlier photo above if my replacement has the dreaded pin - I completed the rebuild before I became aware of these pins !|
|John M Platt|
|I had a look for that when you first posted it. Unfortunately it looks too far gone to tell.|
|those are some scary pics|
just for claeification, are you guys riding the clutch at stop lights? I doulbt you are, So why so much wear, I cant help belive that there must be some constant cantact...esp. for under 12,000 miles
Then agian, I hear the little 8 year old chinise girl that makes ALL of our condensers has a twin sister that works in the throw out bearing part of the company...LOL
This thread was discussed between 19/08/2010 and 24/08/2010
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.