OK, so I've been waiting for my brother to post a question up here to figure out a problem he's got with his Clubbie.. but he's going to lose a wheel before he gets around to it, so here goes.

A few weeks ago he replaced the front (tapered) wheel bearings on his 7.5" disc front end, and ever since the left hand side has been breaking split pins, with the hub nut threatening to part company with the car, taking the drive flange and disc with it.

When the bearing were replaced, he torqued the hub nut all the way, then backed it off a touch to fit the split pin (he said something about the new bearings needing to be backed off as well so they don't seize, makes sense).

Now, AFAIK there should be no torque whatsoever on the hub nut -- it's job is to hold the drive flange in place, while the shaft splines transfer the torque from the shaft to the flange. Thing is, he's regularly shearing the split pins and only finding out about it when the car starts to wobble or the brakes disappear.

Any suggestions?

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Simon

The adventures of an owner builder in the Tallarook Ranges

If you are talking about the Driveshaft nut, it should have 150 ft/lb of torque on it.

Shearing split pins shows that there is too much movement in the hub....he has probably done permanent damage....please get it fixed before your Brother loses a wheel and has a major accident.

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Sounds to me that you need to take it to a Mini mechanic/specialist. Incorrect torque on the hub nut is a good way of floggin out the splines in the hub.

Regards

Daniel

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Also remember that it is 150ft/lb then keep tighting till the next hole is lined up. Never back it off to fit the pin or you will just do what is already happening.
Cheers Pete

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By that I mean no DRIVE torque is applied via the drive shaft nut, not that no torque should be applied to it during assembly..

The other thing is that these were new tapered roller bearings for the disc front end. Is there a breaking-in period with these? Should they be torqued less during this time to allow them to bed in without seizing?

<Still waiting for Smegger to chime in here and explain this first hand, it's his car, after all >

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Simon

The adventures of an owner builder in the Tallarook Ranges

My first question is why did he change the bearing in the first place - was it noisy or was there just play (loosness) in the hub?

If it was because of play, then that have been because the old bearing had been spinning on the shaft and worn it down. Changing the bearing won't fix this because the problem is that the shaft is now undersized where the bearing sits.

The symptoms seem to be that the pin is breaking, allowing the nut to come loose resulting in play around the bearing. What actually happens is the reverse. When you tightent the nut the bearing catches on the edge of the worn part of the shaft - everything seems OK when you use your hands to apply a little preasure to check for movement in the wheel. BUT, when you drive it, the bearing re-settles back into the worn area of the shaft, the wheel becomes loose on the shaft and it's movement and the preasures it receives from all angles during steering, braking and acceleration forces the nut to turn and shears the pin.

Time for a new CV.

When all else fails read the instructions!!!!!
Better get yourself a manual, a proper BMC/Leyland one, not an aftermarket one.
Tighten the nut to 150lbft and continue tightening until the split pin holes line up. DO NOT BACK OFF THE NUT to fit the split pin!
The bearing arrangement is designed to have a preload which is achieved by the thickness of the spacer between the bearings and tightening the nut to the specified torque.
The spacer is sized to fit each bearing KIT. Unless you know what you are doing and have a decent workshop with a surface grinder you can't buy the bearings individually and use an old spacer and expect them to fit with the correct preload. The preload is around 0.001"/0.002". Other cars may have no preload on the wheel bearings but not the Mini. The same applies at the rear.
There is no break in period for the bearings.
Since its all come loose you will have to pull it apart to check for damage and start again. The bearings will still probably be OK but the other bits may not be.
The hardest part of the job is trying to find a way to stop the drive shaft turning while you tighten the nut. I use a bit of angle about 3 ft long with 2 holes that fits on the wheel studs and hits the ground to stop the shaft from rotating while you loosen and tighten the nut.

Hope this helps.
RonR

I have had this happen to me before and i did not figure it out for a while but it was the drive flange the part that screws to the disc itself.
the back face where the bearings run will be worn out and have lip on it.
replace this about 100 bucks and tourqe up the nut to 150flbs.

Grant

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I guess I should throw my two cents in

Firstly, the bearings were replaced thanks to a mainstream mechanic telling me they were (both) worn. Foolishly I listened without actually checking (or realising there were no symptoms of wear) and bought two replacements.

They're tapered roller bearings, not the enclosed type, since I have a disc front. I can't remember why, but at the time I was positive they needed to be tightened (can't remember the torque), then backed off .25 of a turn, and the pin fitted. From memory it was on the instruction leaflet that came with the bearings.

It's worth mentioning that I've only lost the split pin on the one side (front left), but both corners were fitted the same.

The logic behind backing them off was to prevent excess pressure on the taper, which would cause excess heat.

I'll pull the wheel & hub off this afternoon and check the damage.. assuming all is well, I'll torque it up to 150 & fit the pin.. hopefully I don't snap my driveshaft as a result

As far as reading enclosed instructions - the ones that come with these bearings contain instructions for about 4 (or 5?) different hub designs. These instructions completely conflict each other so yes will be completely wrong if you do not follow the instructions for your hub type (pre-load required). I've only ever dealt with ye-oldie cars so was really surprised to hear that some/most modern hub designs run with no load...they just wiggle about in there quite happily. Apparently RAV4's commonly fail WoF's because the hubs feel loose, but they're like that by design.

Right, looks like I'm tightening the sucker right up then

OK, the plot thickens

After tightening as required (which took alot of work.. it was *tight*), and driving liberally for a few weeks, I've just walked out and found the split pin missing again. When I fitted the last pin, there was absolutely no lateral movement in the shaft assembly, and I did not slacken off the nut to fit the pin.

Before I make the trek to a mini mechanic, can anyone think of another reason this could be happening? To recap, after replacing the taper bearings on both front corners, my front-left repeatably loses the driveshaft-nut splitpin, allowing the nut to loosen and the potential for a nasty surprise. Thanks!

Hey, I missed this reply before.. I'll have it all off the car later this afternoon, so will take a look. Can you tell me the logic behind the back face wear causing the problem?

Anything else I should be looking for whilst I'm in there?

here's what happened to my disk rotor at Wakefield Park after the split pin came out and the hub nut undid itself and was hanging on by 3/4 of a turn... you can see the ridge worn on the drive flange face on the inside.

It is always the left one that undoes because the direction of rotation of the wheel makes it come undone, whereas the right hand rotates and does the nut up. Left rear hub nuts are left hand threaded, I guess it was too much hassle to make left hand thread CV's...

anyway, here's the rotor.... - until it broke, the brake caliper was holding the wheel on, eventually it all got too much for it and it fell to pieces, I still have the broken bits

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