repeated rear wheel bearing fail..any ideas?

[clift_d]

yeah dunno whats going on ...no signs the last bearing had span

if the drum openings were say slightly egg shapped woud the bearing still force in or what ? the outer shell is fairly hefty i cant see a slightly iffy opening deforming a bearing but then what do i know lol

That's what can happen with the bearing housings on VWs when they oval. If the damage is not too bad some have been able to achieve a fix with a bearing fit compound, but if the bearing is sloppy in the housing then it tends to fail really quickly.

 

[steveo3002]

the hole in the housing /drum will quite easily deform a bearing, the drum being much larger dia will try keep its shape even if that shape is now oval, so the round outer race of the bearing will now become oval the same as the disc, the outer race then will have highs and lows ie more load on bearing where it is forced inward.
just because the bearing race is made from hard metal that doesnt mean it will stay in shape, it WILL deform, it requires the housing to be the correct shape also and then the whole assembly is equal
if the housing for instance is too small it WILL reduce the bearing diameter slightly ( and expand the housing )
My gut feeling is the drum has been out of shape for awhile now, and now it has cracked and will not hold the bearing tight.

beginning to wonder if theyve been duff all along

the common factors are
same drums
same monkey with spanners
same stub axle that never caused any bother over 10 years

is it a common thing for new ones to come deformed ? i just trust new things are right but now i dunno so much , would i have seen pinch marks out the outer shell where it was too tight ? all looks even if thats anything to go by

 

[clift_d]

You'd need to put a vernier on it to check, but given the amount of poor quality parts floating around it would hardly be a major surprise.

 

[gordon stephenson]

Is there a chance that the old bearings, Locked up at any point and spun in the hub?

 

[steveo3002]

no signs that it did

 

[daedalusminos]

If you have a binding brake, and the drum gets hot it can distort when you put the handbrake on.

 

[normspanners]

would i have seen pinch marks out the outer shell where it was too tight ? all looks even if thats anything to go by

I doubt it !! if the bearing started to enter in the hub ok and it was only a few thou oval as it progressed (that is all that it would take) as it moved into the bore the hardness of the bearing would allow it to slide in without making witness marks. What would poss show a marking, would be to remove the inner races and look for witness marks (heat) etc in the outer race in two places 180 deg apart.

 

[normspanners]

If you have a binding brake, and the drum gets hot it can distort when you put the handbrake on.

that is very unlikely I have seen drums at virtual red heat on rallies and they survive, it is common for discs to be past red getting on for white, in belgium when we bled the brakes it was common for the fluid to spontaneously ignite in your face

 

[daedalusminos]

I was talking about drums where the shoes exert uneven forces on the drum.

 

[normspanners]

If you read, my post, so was I with the old ferodo vg 95 linings they didnt start working properly until they got to about 300/400 deg and went up to about 750 degs and as stated the drums stood it no problem.
the one thing that does happen at high temp is lining deposition onto the disc or drum brake face when applied hot.
That deposition then gives you the feel that the drum or disc is warped.

 

[daedalusminos]

Ahh OK, I was talking about standard drums such as those that might be fitted to a standard Mk1 Focus

 

[Bill Edwards]

Despite being extremely hard bearings do distort as norm says.
It's quite possible to force a bearing into a hole to the point that it will barely turn (notchy). Obviously they don't last very long when this happens!


Interestingly when you force a bearing onto a shaft which is too large it cracks the inner race. Not having another bearing to hand I have used bearings with the cracked race and they can run for years without failing.

 

[Bill Edwards]

Hum and 'WE' hope he isnt a member of a welding forum with a pseudonym either----- I believe.
not forgetting this is in a public domain !!

I don't think welding holds any interest for him, but he's considered to be the village idiot by just about everyone who knows him. I don't think it should come as a great shock if someone were to tell him!

Still they would slacken so we ended up using some loctite that needed applying and then tightening so fast if on a hot shaft, we had to use a 3/4 nut gun and torque immediately otherwise the loctite would lock the nut on the thread, if we took our time running it up with a ratchet, it would lock so solidly we could end up torquing the nut up on the locktite itself, IE the nut had not gone fully home.

Interesting, which Loctite were you using and how hot was the shaft?

 

[wookie]

A classic example of having to 'over torque' a wheel bearing was the MG METRO 6R4 we could NOT get the CV hub nuts to stay tight it was a constant battle,

Was this on both sides ? If not then could it have been solved by having a left hand thread ?

 

[normspanners]

Was this on both sides ? If not then could it have been solved by having a left hand thread ?

All of them, it was the sheer power being transmitted and the shock loading of the wheels lifting and landing with 400 HP and incredible high

v6 normally aspirated engine torque, poss going to one shaft at times, with F1 size sticky slicks might of had summat to do with it

Interesting, which Loctite were you using and how hot was the shaft?

We had some special locking fluid not sure of the spec now most loctite is supposed to release with high temp this stuff did the opposite, was a bit like concrete !! coz as said earlier the discs would be glowing cherry red at times so some of that temp would pass to the shafts,all the stuff was that hot the brakefluid when released would burst into flames as the oxygen got to it. it was welding glove, time to touch most things especially in belgium or france, when they came out of a stage and straight into service, with no road section to cool down, I changed a ZF gearbox once on mk2 escort, just threw it out from under the car, when we had finished 10 Minutes later and the car had gone, and we started to pack up the gearbox had melted into the tarmac.

 

[normspanners]

Ahh OK, I was talking about standard drums such as those that might be fitted to a standard Mk1 Focus

these where std drums on group one escorts, everything had to be standard for the production championship and mk2 rs 2000 had drum rears, as was on a production car and checked at scrutineering before and after the events we could fit different spec brake linings and front pads ( for safety) to stop fade but everything else was std
we used to used DS11 pads or mintex 171's and VG 95 linings. they only started working when hot, and was a bit disconcerting on first morning braking. but as they started to warm it was like a servo kicking in.

 

[wookie]

I changed a ZF gearbox once on mk2 escort, just threw it out from under the car, when we had finished 10 Minutes later and the car had gone, and we started to pack up the gearbox had melted into the tarmac.

You know this could become a thread all of it's own, "Norm's tales from the mad days of rallying". I'm sure there would be plenty of interest. I seen a few docs on the days of group B madness but they never tell the tales from the mechanics side, mores the pity.

I used to work with a guy that was into classic rallying, some of the tales he told me of what they got up to had me in stitches.

 

[Bill Edwards]

We had some special locking fluid not sure of the spec now most loctite is supposed to release with high temp this stuff did the opposite, was a bit like concrete !! coz as said earlier the discs would be glowing cherry red at times so some of that temp would pass to the shafts,all the stuff was that hot the brakefluid when released would burst into flames as the oxygen got to it.

If you ever remember what the special locking fluid was I would be grateful, as it sounds to be very useful.