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Mini Clutch Thrust Bearings
https://www.ausmini.com/forums/viewtopic.php?f=2&t=91516		 Page 1 of 1
Author:  OnSafari [ Mon Jan 11, 2016 1:54 pm ]
Post subject:  Mini Clutch Thrust Bearings
So what are people using and what is the best quality option for replacement?

Mine's knackered.

Thanks
Author:  drmini in aust [ Mon Jan 11, 2016 2:19 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
Well, the best were Timken or SKF, flat 3W 5-8 ones as used on coil spring clutches up to ~1965.
Both these are NLA now.
If buying the later one 7W 5-8, try and get a UK, or EU, or Japanese made one.

I run an orange dot clutch, the release bearing is a stock RHP 7W 5-8 one. Done 18,000 miles so far and still good. But, I don't ride the clutch or hold in gear at the lights. :)

[edit] when fitting, press on the centre of it, NOT the outer face. Otherwise you can brinell the bearing tracks and it'll fail soonish.
Author:  Curly [ Mon Jan 18, 2016 1:25 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
This is what I find happens to those crappy new-fangled clutch release bearings (7W 5.8 ) - Note the blued contact surface and how the outer ring has collapsed backwards and is now locked up, off centre. Admittedly this one is on a competition car with a grey dot pressure plate, but all the same, the design is all wrong :evil:
The old style SKF bearing (3W 5.8 which is no longer available) is shown at the bottom of the picture and it will replace the buggered one.
I can't understand why some bearing company hasn't started making them again. The demand is obviously not as high as it once was, but I'd be prepared to pay a premium price for a decent product and I dare say others would as well.

Image
Author:  Timbo [ Mon Jan 18, 2016 3:31 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
I agree completely. I've experienced exactly the same with those rubbish 7W 5-8s the center basically just pushes out of them.

I'm told that there's another option. Apparently a 5203RS bearing can be fitted, with some machining of the the thrust plate to enlarge the centre hole. Its a dual row angular contact bearing which apparently stands up to the pressure very well.

Tim
Author:  TheMiniMan [ Mon Jan 18, 2016 7:22 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
Ive used the Metro bearing & carrier a number of times (on the early clutch/flywheel)
simply out of curiosity & also the fact that i was out of the early carriers at that time
& so far they`re all still going well

one of the main problems with the 7w bearing isn`t so much the bearing
more the fact that most people who have experienced such premature wear with them is that
they have over-adjusted the clutch & the bearing is running on the thrust washer the whole time,,, instead of just when you use the clutch

i`m not saying that everyone over-adjusts the clutches, but it really is a common thing

also people sitting their foot ontop of the clutch while you`re not using the clutch does run the bearing on the thrust too.

so,,, simply set-up your clutch travel systems properly,
with decent amount of free-play,
adjust it correctly...
stay off the clutch
& all will be well

but in saying all that---> i really do like the older 3w bearing too
it is a far better bearing & i`d like to use one in every clutch job we do

but it really doesn`t matter what bearing is in there if you`re not setting the clutch up
properly with the correct amount (or even more) free-play
&/or if you rest your foot on the peddle all the time

carry on,,, i`m just adding my 25cents worth :-)
Author:  Curly [ Mon Jan 18, 2016 9:04 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
Thanks for your insight Matt, but the setup clearance and adjustment had no bearing (pardon the pun) on the failure of the component in this case. More likely it was the repeated and sudden acceleration of the bearing from 0 to 8000rpm whilst compressing a grey-dot pressure plate spring that had something to do with it. :roll:
Author:  TimW [ Mon Jan 18, 2016 9:39 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
They originals are hard to get. I managed to get one of the original style bearings from Heritage MG in Smithfield, Sydney, 6 months ago for $90 ea.
Author:  TimW [ Mon Jan 18, 2016 9:41 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
http://www.mgspareparts.com.au/images/s ... %20003.jpg
Author:  drmini in aust [ Tue Jan 19, 2016 10:48 am ]
Post subject:  Re: Mini Clutch Thrust Bearings
I have just bought a 5203-2RS bearing and done some measuring.
The hardened thrust plate on the diaphragm cover needs about 3mm machined or ground out of its bore to clear the inner ring of the bearing with a bit of clearance. ie. bore out from 25.5mm to 28.5mm.
[edit] Try a file on the thrust plate. If you find it is soft, toss it and get another off an old diaphragm. Some recent diaphragms were supplied with a soft thrust plate. I think that problem is fixed now.

Also, this 5203 bearing is 17.00mm bore, not 15.85mm (5/8)- so a steel or brass bush needs to be made to allow fitment onto the clutch plunger.

[edit] After looking at Curly's pic in his post below, it's obvious that the thrust plate in these modern diaphragms does not run anywhere near concentric. To use the 5203 bearing with it running like this, the thrust plate bore would need enlarging to 30mm or so.
GR puts the 7W5-8 bearing into a flat faced cup, so it doesn't gouge the plate.
Author:  Curly [ Tue Jan 19, 2016 1:05 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
drmini in aust wrote:
Try a file on the thrust plate. If you find it is soft, toss it and get another off an old diaphragm. Some recent diaphragms were supplied with a soft thrust plate.


As the good doctor says, "Check the hardness of the thrust plate".
The plate on the left was from a customer's car that came back twice within a couple of weeks to have the clutch adjusted. The problem turned out to be a soft thrust plate that was having a groove worn into it by the thrust bearing (7W 5-8) The groove was 0.075" deep and the material was so soft it could easily be marked with a centre punch (see pic).
The plate on the right is from the competition car that had the seized thrust bearing described in the thread above. It's a good old hardened unit that hasn't even marked up, but the blueish tinge is evidence of some serious heat issues, so to be on the safe side it's being replaced by another old, hardened unit from my stash of spares.

If there are any metallurgists out there, I'd be interested to know your opinion on whether the plate on the right has been weakened by the heat which created the blueish tinge. I'd rather not throw it out if it will still perform its job satisfactorily.

Image
Author:  Hobson [ Tue Jan 19, 2016 1:28 pm ]
Post subject:  Re: Mini Clutch Thrust Bearings
Might be able to con Hoopers into making some to spec. originals http://www.hooperbearings.com/
Author:  drmini in aust [ Sat Jan 30, 2016 9:20 am ]
Post subject:  Re: Mini Clutch Thrust Bearings
I have now bored the hardened thrust plate out to 29mm dia. These plates are (should be) case hardened, they are soft inside. A carbide tipped tool cut it OK.
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