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MG MGB Technical - carbon thrust thickness

Do any of you chaps have a new carbon thrust in your workshops, I am interested to know how thick they are when new (Borg &Beck) I renewed my clutch about 20,000 miles ago, and I now have the car completely stripped to go for a paint job, I took the box off to renew the front cover seal, while the engine is out, and I am thinking about putting a new thrust in.
Andy Tilney

I do have a new one - or maybe two - in the garage, but I'm away until Wednesday, so I can't check.
Dave O'Neill 2

Thank you Dave for your reply the body is going away next week for a re spray, and will be away for a week, so there's no rush, I am not going to start putting it back for a couple of weeks,
Andy Tilney

An AP I have had a long time is 17mm overall, 5mm proud of the casting.

How long did the old clutch last you? Mileage can be irrelevant, it's all about how you use the clutch as to longevity. Given the cost, the size of the job to replace it, and the 20k I'd put a new one in. I'd also be assessing the friction plate.

I had the release bearing casting wear through over 20 years ago so fitted a roller-bearing, but always had problems with it with periodic noises. Also a low-ish biting point that wasn't bleeding and that I couldn't get any higher despite mods to the pedal and push-rod. That broke up a couple of years ago, when the friction plate was barely half worn. It was then I discovered the release arm was holding the bearing way out of concentricity with the first motion shaft, which is apparently very common. I spent some time on the release arm getting it concentric, and then found the biting point was much higher than expected, so reversed my mods to pedal and push-rod. I reckon the offset bearing wasn't pushing the pressure plate in squarely, causing both the low biting point and the failure of the bearings.

If your release arm and bearing is concentric with the shaft, then you could try a roller-bearing. But then, when you next replace the clutch, would you leave that bearing in? So if your use of the clutch isn't causing excessive wear to graphite bearings, and they last the life of the friction plate, roller-bearings are a waste of money.
paulh4

Thanks Paul, my last clutch was the original from 1969, I only changed it after being stuck in a very long and slow moving traffic jam for over 2 hours,and I didn't want it failing later, I have already tried a roller release bearing once before and was not very impressed, it was so noisy on start up, I had to take it out again, which meant two clutches in one day,
Andy Tilney

Paul I have just measured my carbon thrust and its exactly 5mm, Thanks
Andy Tilney

This thread was discussed between 24/11/2017 and 25/11/2017

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