MGB & GT Forum

I see there are 2 possibilities for this, the Carbon one or a new roller bearing.

I have offered to do this job for a friend, and so I'm not sure which one to use, I have always used the B&B carbon one, but is the roller a better option? I guess it could wear the fingers quicker, is my first thought. Are any other parts need to fit the roller bearing, does it have the ears to fit in the fork?

I got the combination one from Basil Adams. It's a roller bearing with a carbon face. Check with Basil.

I have a carbon bearing in the roadster and a roller bearing in the GT. Both have performed well.

There is some disagreement on the roller bearings though. John Twist explains that for the MGB the bearing approaches the pressure plate in an arced manner, thus throwing the bearing off-center as it makes contact. The result is it is not running truly on center of the spinning pressure plate and thus will fail over time. On Triumphs, he says, the throw out bearing is coming straight in on center of the pressure plate and the roller bearing works fine.

Others will say this is hogwash and the only problem with the roller bearing style is that for a stretch of time poor quality units were being sold, and that was why there were failures.

Then on the carbon bearings there was also a stretch of time when bad units were on the market. On those the carbon was breaking apart under pressure resulting in having to open everything up again.

I haven't seen any major complaints in either case here on the forum in recent years.

BH

Hi all-

FWIW - I just installed a new "powerline" carbon TO bearing in my MGB when doing the resto. After 25 miles I suddenly had a terrible cyclical clunking sound when depressing clutch. So, engine comes out of the car, and surprise - the TO bearing has a huge chunk out of it - pieces spread all around the bell housing. Outer metal case was grinding on pressure plate, which fortunately only had minor scratches.

Yes, only 25 miles! I can only assume the carbon material was flawed/cracked and gave up almost immediately.

I had a new Moss carbon one in my supply, so I replaced it. I know there is controversy over which type is best, I hope this one hangs in there.

I just need a day to get everything back on the engine. Fingers crossed.

--Dale

Well there ya go. So much for no "complaints.......in recent years.". And that is one legitimate complaint !!!!

BH

The problem with the MGB and roller thrust bearings is that there is no sleeve over the gearbox first motion shaft, so the release bearing is able to move sideways and up and down. The movement of the arm is an arc so promotes an off centre alignment. This means it isn't concentric with the fingers on the clutch cover and so wear is inevitable. The carbon thrust can accept not being concentric as it's face is effectively lubricated by the graphite, so a little off centre alignment isn't an issue. Most other engines have a guide sleeve over the shaft keeping the bearing concentric. If you like a long read try this from Paul Hunt. He had a roller bearing grind itself to destruction and shows pictures to prove it.
http://mgb-stuff.org.uk/clutchtext.htm#roller

There is (sort of) a 3rd option.

NOS carbon bearings from the 60’s, 70’s, and 80’s still pop up on eBay fairly regularly, and are often cheaper than a new replacement of dubious quality.

The early-hour failures of reproduction carbon bearings are still happening fairly regularly in the E-type world, so I don’t know why MGBs would be immune these days.

John , I installed an uprated Borg & Beck clutch kit 2 years and about 6,000 miles ago ( 10,000 kms? ) and no problems . The photo below shows the setup and as you can see the fingers on the clutch cover ( pressure plate ) are interconnected with a flat plate . Don’t forget the pilot bushing in the crankshaft which can be difficult to remove and the new one should be soaked in motor oil for at least a day before installation.
RudyB

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I know enough to know that I don't know enough.

If the women don't find you handsome they should at least find you handy. Red Green

For those looking, I have the borg and beck pressure plate, disc and roller throw out bearing in stock. I also stocj the heavy duty Exedy disc that has 35% mote friction material (still an 8" clutch - not like the 8.5" TR7 clutch) for less than the Moss AP clutch. Basil 707.762.0974 basiladams@yahoo.com

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Basil C. Adams
1956 MGA Coupe (Show Car)
1957 MGA Roadster (Driver)
1958 MGA Coupe (Racecar)
1959 MGA Coupe (unrestored)
1960 MGA Coupe (unrestored)
1960 MGA Roadster (Driver)
MKIII Elva Courier (E1056)
1967 427 Cobra
1972 Alfa Romeo Montreal
A coupla late MGBs
1960 Austin Healy BN7
More Cars than Brains

I also had one of those carbon bearings that totally disintegrated itself.in short time.

Some 12 years ago I bought a B&B clutch system from MGOC (#1 here). At the same time I bought the roller release bearing (#4) but if you click on it they no longer sell so I can't show it - odd. So far so good - I think (as I haven't had the engine out in the past 9 years). FWIW I replaced the plate with the TR7 version that were all the rage back then. These days if I had to replace the clutch I'd be looking at Exedy's offering. IDK what I'd do for a new release bearing.

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Mk1: CKD 11/66 first registered 8/5/67; owned since 3/77. 18GB +40 balanced. Peter Burgess BVFR head. Piper 285. 123. FidanzaFW. 4synch c/r box. Lots more as I did a nut and bolt rebuild; finished 2015. Tartan Red.

GT: December '78. VW Golf guards, flush fit front and rear valances. Torana XU1 vents, frenched indicators & Mk1 rear lights. 'Worked' Rover V8 with Monsoon ECU for EFI. GM4L60E, Lokar tiptronic & Quick4 controller. Vintage Air A/C. FC IFS. CCE 4 link rear. Salisbury with Quaife. Jaguar Storm.

X2.
Let's not restart this debate once more...

Either one. However, the carbon one is original and lasting. The roller bearing one depends on the the manufacturer. If it is generic or of Chinese origin, I would go with carbon.
Carbon is available made in England or generic. Choose British.

+1

Just do a search if you want to read more opinions than you will ever need to know about MGB throw out bearings.