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MG Midget and Sprite Technical - Rear hub bearing - when is it too worn?

I'm in the process of stripping down my rear hub to replace the oil seal.

With the retaining nut and lock washer removed I could detect very slight movement if I grasp the hub and wriggle it up and down. It is very slight but is perceptible. Is this a normal amount of play in the bearing or a sign of wear. Would it be wise to replace the bearing anyway while the assembly is stripped down?

If I do replace, are there any issues regarding replacements such as those problems with the front bearings?

Any advice gratefully received.
Chris Hasluck

Hello chriss
Am doing my rear axle up as the bearings grumble and the oil seals are solid ,the hub nuts are handed ,and there is a lot of discussion about the torque for the brake hub nut ,mine came apart ok

,

Kevin Stevens

Hi Kevin
There is no grumbling from my bearings and I'm only undertaking this in order to stop the axle oil contaminating the brake shoes. Still, if the play is a sign of wear I'll replace - if normal I'll keep.

Hub nut came undone easily - obviously not done up very tight.
Chris Hasluck

The rear bearing does move a little. Whilst you have it stripped out though I would renew it unless you know its age. There are no issues with the rear bearings and most of the usual suppliers will be fine. There has been a lot of discussion about the tightness of the nut. For me I just tighten it up with a 12" tommy bar. The original tool has a 12" bar so I guessed that would be enough.
Bob Beaumont

Thanks Bob
Chris Hasluck

The most likely cause of oil contamination on the brake shoes comes from the half-shaft seal. Make sure that beds down properly.
Graeme W

Chris,

I had my axle rebuilt using a Speedy Sleeve as the seat for the seal was worn / rough.

HTH
Doug Plumb

Alternatively use a sealed bearing 6207-2RS and omit the original oil seal.
Alan
Alan Anstead

An oversize O ring can help seal the joint. The cross section is bigger. Hardware stores will have them. The ones I have are .125.
J Bubela

Hi Alan
I've thought about using a sealed bearing and fitting the original oil seal as well (belt and braces) but am wondering now whether the absence of oil/grease from the axle/bearing would mean that the seal would run hot in that case. You say omit the original oil seal - is there an effective seal without.

JB I'm certain the half shaft joint is not the problem as it has been worked on several times and oil is still present. The oil seal on the right side had to be changed 2-3 thousand miles ago (about 3 years!!) so I'm sure it is the seal that is at fault.
Chris Hasluck

Chris
One of my members has been running a sealed bearing for several months now. The sealed bearing was fitted as the surface of the back axle casing was worn over time by the original oil seal. A replacement oil seal would not hold back the oil. The sealed bearing holds its own lubricant inside. Apparently sealed bearings come in several types and the one above is the one to use.
Alan
www.kentmasc.org
Alan Anstead

Chris,

Growler, South once wrote here:
And I shall start raving about fully-sealed bearings (you know, the pre-lubed type with integral oil seals)
They're lovely. Last forever and supplement the existing oil seal- no more leaks, and no more damaged bearings from differential metal flakes.
SKF part# 6207zz
NSK part# 6207vvc-mav2

The procedure to get and keep a oil tight seal between brake shoes and differential is a pain in the ass:

I sand the axis where the oil seal touches the metal with fine sanding paper. If it is not smooth there; use a speedy sleeve and a new oil seal 1(5) coated with silicon grease. Use a new O ring (14). The paper gasket (13) should not be to thin or to thick. I usually have to trim the gasket to fit! I always use hylomar blue to coat both sides of the gasket. I do compress the gasket with 4 wheel nuts (23) with bigger screws under it, immediately after letting dry the hylomar for 15 min and let it dry for 24 hours after compression. Before you take off the wheel nuts be aware that the the screw (17) that secures the wheel drum is the only device that compresses the seal. Put all the power you have on that screw. Cornering fast with the wheel nuts on less than 50 can break the seal.


Flip Brühl

6207ZZ is a shielded bearing so will not be oil tight, they're not intended to be. 62072RS is a sealed bearing. I can't find information on the NSK designation.
David Billington

Yes indeed David. Has the number changed? I use the double rubber ones for 14 years and 100.000 km now. Thy are used in washing machines as well. I picked up this photo from the internet. Is this the one?

Flip

Flip Brühl

David
I think the NSK sealed bearing is 6207/ddu/nsk.

Flip
That's the one I've just ordered.
Chris Hasluck

I used the sealed bearings for 4 years without any issues. I did put the lipseal in as well (known as Belt and braces!)

Potentially the half shaft joint becomes a problem every time you disturb it. I have found that removing the wheel nuts and taking out the counter sunk screw is enough for oil to pour out!
Graeme W

When you remove the wheel nuts, there should still be three screws holding the joint together, until you remove the brake drum.
Dave O'Neill 2

If you search earlier threads you will find discussions on how tight to tighten the rear hub nut and what to use to do this instead of the factory service special tool.

In addition to suggestions to use Stilson pipe spanner and sockets etc, you can buy thin spanners made for the job, e.g.

http://www.ebay.co.uk/itm/262103559413?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
&
http://www.spriteparts.com.au/shop/accessories.html#RearHubNutSpanner

Best wishes
Mike
M Wood

I think there is only a single screw clamping the halfshaft seal together once the pressure from the wheel/drum is removed. never seems enough to me!
Graeme W

Graeme, are you describing steel wheels or wire wheels?
David Smith

I think it was the same in both David. The manual refers to a single screw as well.
But I am going by memory (not the most reliable!)
Graeme W

On a slightly different tack, I've just replaced the halfshafts on my frogeye with later stronger shafts, and whilst doing so cleaned out and checked the rear wheel bearings.
Normally I would pack wheel bearings with grease when refitting, but it struck me that maybe I shouldn't do this, as the rear bearings must be lubricated by the hypoid oil that sits in the axle casing?
There must be oil sloshing around in the hubs as otherwise there would be no need for the paper gasket and rubber o ring?
Or have I got it wrong?
Maybe I'm worrying too much, and it doesn't matter whether you grease the bearing or not?
On the other hand I wouldn't want to unnecessarily contaminate the lovely clean (and relatively expensive) hypoid oil that will sit in the axle casing.
Were the back axle casing and wheel hubs designed as they are, precisely so that the hub bearings would be lubricated by the same oil as the diff?
I've searched for 'rear wheel bearing lubrication' in the archives to see if this has been raised before, but haven't found any reference so far.
My workshop manual doesn't say anything about packing the bearings with grease, but maybe it just assumes you would do it as a matter of course?

My apologies if this is a stupid question which has been covered before now, or elsewhere, but any thoughts please?
Many thanks
Phil
P J Dent

Phil....

What an interesting post.

My thinking goes something like this.

The bearings are lubricated by the gear oil in the diff/axle by design, but that may not be ideal. In other words I have the feeling that it was something of a compromise. Maybe sealed for life bearings were not readily available at the time, or were prohibitively expensive for the factory to use. Also factor in the thought that these cars were not intended to last more than ten or twelve years so possibly a compromise on wheel bearing life was not a significant issue.

However; nowadays properly sealed bearings are readily available and not expensive. The "2RS" part of the bearing number is the giveaway.

I would be tempted to use them in your place and let the hypoid oil look after it's primary function in the differential gear. There's nothing wrong with improving on the original spec if you think it was less than ideal.

Any thoughts on this guys and gals?
Greybeard

My rear brakes were shockingly bad, I found that paper gasket had leaked severely on the nearside and everything was well lubed as a result!! :(


John..

j b biggs

Yes, the bearing is well lubricated by the diff oil, witness how easily leaks appear if the seals at either the hub or the axle flange are defective. I have never seen any bearing relying solely on diff oil to lube it fail due to lack of lubrication.

Or indeed in the case of the hub seal, sometimes it can leak when both seal and axle housing are perfect and the car is cornered in a spirited manner (track day).

Similar to others above we have solved this by the use of sealed bearings.
Paul Walbran

I'd not used a brake adjusting spanner in years too, Luckily I still had a couple in with the tools!! :)

j b biggs

John: that also happens to the unwary who remove the drum and start to remove the half shaft without ensuring any diff oil has drained back or without having removed the shoes "just in case".
I made a "bib" out of the flexible plastic cover of an A4 folder which I can tuck under the join before I undo it to ensure the shoes are protected.
None of this will help leaks during normal use however!
Graeme W

Thanks Greybeard and Paul for your comments on my post, and my back axle is now back together without any grease in the hub bearings.......and no back axle oil leaks so far! Off for a test drive this morning.

I can't really justify new sealed bearings for the moment especially as my existing wheel bearings seem super smooth. However, I can see that fitting them is probably the best solution in the long run.

I guess rear wheel bearings have a pretty easy time of it compared to front wheel bearings as the car is relatively light at the back, so I'd be surprised if they wear out very quickly, certainly in my lifetime. Mind you, just saying that is asking for trouble!

So conclusion is.....front wheel bearings need packing with grease when assembling, but rear wheel bearings don't.

Many thanks for clearing this up.
Cheers
Phil
P J Dent

The workshop manual notes packing bearings with grease, I assume this could be a precaution, as following the initial build sufficient oil may not reach the bearings on level surfaces.

I've not seen any grease remain when stripping used bearings and again assume its been washed out by the oil.

R.
richard boobier

This thread was discussed between 18/10/2015 and 24/10/2015

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