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MG MGB Technical - Latest on clutch roller throw out bearing?

This is just for my education and whenever I will pull the lump in the future.

What I undertand is the carbon bearing works due to the fact it engages in an arc. Whereas the roller bearing prefers a direct horizontal engagement.

Owning the car for quite a while and having to pull the lump due to the carbon bearing wearing down before the clutch/engine does I always had high hopes for a roller bearinge execution.

Since all the parts sites now offer rollers does anyone here have experience with them? Or know if the characteristic of the MGB clutch throw has been resolved so these work correctly,

And no, I never leave my foot on the clutch pedal. However I do get stuck in a lot of traffic. So the throwout gets a good workout.

Yes, I alway replace the fork bearing and make sure its functioning properly.

This has just been a long fascination so your experience is welcomed.
Max71

"the carbon bearing works due to the fact it engages in an arc."

Not 'due to', but it copes with the changes in concentric alignment with the first-motion shaft as the clutch is operated and released better than a retro-fitted roller bearing can. OEM roller bearings as in the 1500 midget and V8 are kept concentric with the shaft by sliding on a tube fixed to the gearbox front-cover, that the shaft projects through (http://www.mgb-stuff.org.uk/v8rb.htm#4). However even a graphite bearing has its limits. Mine failed soon after getting the car 27 years ago, and I thought I was doing the right thing by fitting a roller. However that has been nothing but trouble making various noises on and off virtually the whole time since then, until last year when it became evident that it was on its last legs. I changed the clutch (very annoying as the friction plate was barely half-worn) and used a standard graphite graphite, but examination of what can only be called 'the remains' of the old one and the positioning of the arm showed that the arm was very badly off-centre side-ways from the first-motion shaft, as well as the inevitable change in in-line centering as it operates - http://www.mgb-stuff.org.uk/clutchr3.htm#5.

I spent some time correcting the sideways misalignment ... only subsequently realising that if I had done nothing except bang a new one in I'd probably be over 90 years old when it next needed replacing ...
paulh4

I mispoke - that is what I meant.

and YEOW. What a nightmare. I had no idea and now I'm trying to remember if my TO bearing fork was centered. I was very careful last time to make sure there wasn't any wobble however you did a superb job.

The reason I was hopeful the new versions would work better was due to the carbon failing way too soon with traffic usage many times. This photo is a carbon that has maybe 20K on it. The clutch plate was barely worn and the flywheel looked perfect. Since we all have to pull the entire engine and trans its a lot of commitment just for a throwout bearing.

For passing interest do you see any new design to the new TO bearings. Knowing the fork must be centered although your story and shot have pretty much scared me off.




Max71

That's well worn. In theory if it is correctly aligned it should last longer than that as the boss on the cover plate is usually slightly smaller than the bearing casting. However any misalignment would prevent that, and if the casting is rubbing on the cover plate that's when you get noise, vibration, and a more noticeable drop in idle revs as you put the clutch pedal down.

The attached is an 8k bearing, where the graphite ring was secured in the casting with a roll-pin instead of bonding. There were no bits of graphite in the bell-housing, just masses of black dust. Fortunately this design was relatively short-lived (in both senses) and they have gone back to bonding. Watch out for old stock though.


paulh4

This thread was discussed between 22/01/2017 and 23/01/2017

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