Fitting new front hub bearings

[Mr Don]

I am being given conflicting advice and need clarification.
I am about to fit new bearings to a stub axle on my moggy.

Which way round do they go?
Thick sides both towards the king pin.
Inside bearing thick towards the king pin, smaller outside bearing thick side to the nut.

Your advice would be appreciated

[bmcecosse]

The thrust faces must oppose - I dunno about 'thick' faces. But probably that is the thrust face.

[Mr Don]

Makes sense. Thanks Once again
Apparently the thrust face is usually the side engraved with the part number.
One book states the thrust, engraved sides, should face the spacer tube.
I will contact the company who supplied the parts to see what they say.

When I dismantled the stub to change the trunions for MOT, the bearings were a sod to get off and broke apart. If what I read is right the ones on the car were both the wrong way round.

Me thinks I will pull the other side to check it out.

Regards Don

[bmcecosse]

As long as they oppose - it doesn't really matter which way round they go - as long as they oppose.

[IslipMinor]

As long as they oppose - it doesn't really matter which way round they go - as long as they oppose

I disagree - it matters a lot which way round the bearings are fitted. That is why the instruction is that the 'THRUST' sides must face each other - they are angular contact bearings and are designed to work one way round only. The problem is that the thrust side is not clearly labelled as it used to be - the diagram below helps to identify the correct way round to fit them:
[frame][/frame]

Mr Don, This is basically the same as your 'Inside bearing thick towards the king pin, smaller outside bearing thick side to the nut' - but it is the inner race that the 'thick' refers to. The 'thick' part of the outer race should face each other once fitted into the hub.

Would be very nice if the shims that are suggested were actually available.

the bearings were a sod to get off and broke apart

If you needed to use a puller to get the hub off and the inner part of the inner bearing was left behind, this is quite normal and shows that the inner bearing at least was fitted the right way round!

If the bearings are in perfect condition, they can be cleaned and reassembled. Thoroughly clean all parts of the bearing and balls, put all the balls back into the cage using grease to hold them in place, put the outer (larger diameter) race with its 'thick' side down on to a flat surface, push the cage and balls over the inner race using more grease to hold it together, place the inner race and balls/cage into the open end of the outer race and make sure that everything is level, then using a copper faced hammer, hit the inner race sharply and it should 'pop' back into the outer race! Sounds a bit brutal, but it is the only way to do it unless you have a small press, or a large vice.

Once reassembled, clean everything again and re-grease prior to fitting back into the hub.

[katy]

Would be very nice if the shims that are suggested were actually available.

Not hard to make shims, the trick is to figure out what thickness is required to get it right.
Once assembled the bearings should not have any play and be lightly snug but not tight.

[bmcecosse]

I maintain as long as the bearings oppose - they will each react to thrust just fine. Why would they not? And any front hub I have removed has just pulled off the shaft - either by hand, or with the slightest assistance from two tyre levers - acting on the wheel cylinders. Never had the bearings disintegrate - and never had to renew any front bearings!

[Mr Don]

Thanks guys and gals.
I contacted the supplier and followed the instructions from the the bearing supplier.
I feel the one that broke up on the car was fitted the wrong way around. But my mechanic mate does not think so.

Are the internal matting surfaces tapered, or parallel.

I feel a set of pullers coming for Christmas, not going through that malarky ever again.

[bmcecosse]

As above -a couple of tyre levers are all I ever used - but another solution is to refit the wheel - and wiggle the hub off that way. Pullers should definitely NOT be required.

[IslipMinor]

I maintain as long as the bearings oppose - they will each react to thrust just fine

Roy,

No they will not. They are asymmetrical bearings and must be fitted with the 'THRUST' side facing each other - why would the design and fitting instructions make this point very clearly if it didn't matter? You would not suggest fitting taper roller bearings the wrong way round, so why angular contact?

Fitting them the wrong way round will make the bearing try to pull itself apart, with potentially very dangerous results – there is virtually nothing to prevent the outer races coming out of the hub, other than the ‘fit’ in the hub (which may have become minimal after a number of bearing replacements) and the lip on the outer race (which, as many people have found, offers little resistance to the bearing being pulled apart), and the whole hub collapsing.

You may have been lucky enough not to have had to use a puller to get a front hub off, but I would expect that most of us at some time have had the joy of the inner bearing coming apart and then having to get the inner race off separately. If it does happen, it is worthwhile, with some fine wet 'n' dry, very carefully easing the stub axle journal where the inner race fits - this needs to be done VERY carefully, using a bearing to check when it will just slide on, but with some resistance. If is it slack, it can only get worse in use.

[katy]

Ditto

[bmcecosse]

I can't see the bearings coming apart - they are fully supported on both sides, after all thrust is thrust - it comes from both directions - so as long as one bearing is able to take the load - it's fine. Taper rollers can be and sometimes are fitted back to back - same rules apply. I believe if the bearings are not a 'slide' fit - it's because of previous damage to the shaft - or someone has handily fitted them using Loctite!

[IslipMinor]

They are NOT 'fully supported on both sides', that is why they 'fall apart' if the inner race is very tight on the stub axle. They are designed to take axial thrust in one direction only - hence they are used in back-to-back pairs. In a completly different application they can be fitted the opposite way round, but the clamping is then on the outer races. In the Minor and other A-Series engined applications (Sprite, Midget, A30/35 etc.) it is the inner races that are clamped and the outers are a press fit, but otherwise unrestrained.

If they are reversed in the A-Series hub configuration, the axial load (thrust) is resisted only by the combination of the interference fit of the outer race in the hub by one bearing and by the lip in the outer race in the other. Reverse the direction of axial load, and the same situation applies, just to the opposite bearings. There is NOTHING to properly resist the axial load, the outer race of one bearing will move in the hub and the ball race will move in the outer race in the other, and ultimately 'pop out'.

Whichever way you look at it, it is extremely dangerous to reverse the Minor front hub bearings.

[bmcecosse]

We'll just have to agree to differ on that one Richard!

[IslipMinor]

No Roy, I cannot agree to differ on something that is outright dangerous to do.

Anyone else have a view on fitting Minor front hub bearings the wrong way round?

[mike.perry]

I think that I will go out and take my front hubs apart!
I am using prepacked sealed bearings on the front hubs of my Series MM which have been converted to fit M1000 swivel pins.

[RobThomas]

Islip is correct.

[IslipMinor]

Thanks Rob - it was getting a bit lonely out there!

I have frigged the diagram posted earlier to show the bearings fitted the wrong way round, which should help to demonstrate that there is no proper axial location and that the hub will move under load either inwards (a little, as the limit is that the drum will grind on the backplate, or the hub on the upright) or outwards (the wheel will fall off, which is the really dangerous bit) .[frame][/frame]

[Declan_Burns]

Excellent diagrams Richard!
Regards
Declan

[Rasputin]

As the original workshop manual says;On car no 228267 and subsequently,the front hubs are fitted with angular contact bearings and solid bearing spacers.When replacing these it is important to place the thrust side of each bearing towards the spacer.The thrust side is that side which carries the bearing part number.