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MG Midget and Sprite Technical - Rear hub nut torque

I'm about to replace the LH rear axel oil seal, I know the hub nut is a LH thread but what should I torque it up to? None of my manuals has a figure for this and I've seen everything from just tight to 140 ft/lbs. I seem to have a distant memory of trying to tighten one to 140 lbs only to strip the thread in the nut. I'd welcome others thoughts on this. Thanks Bob
R.A Davis

My bmc workshop manual just says tight. I have done it that way for many years without any problems. I also put some loctite on the threads as sometimes the nut becomes loose as the lockwasher is crushed.
Bob Beaumont

There is no figure as Bob B says, just tight. The 140lbsft figure comes from the rear axle pinion nut which some mistake for the rear axle hub nut.

I've seen a figure for the maximum torque this nut will take given it's diameter, thread pitch and nut thickness and that was 200+lbsft. I can't remember where I saw that figure but it stuck in my mind.
Rob
MG Moneypit

Rob beat me to it.

I was going to say that the torque figure could be calculated using those criteria.

The BMC manual for the early MGB (banjo) axle gives a figure of 180lb/ft, although the thread is a slightly larger diameter than the midget.





Dave O'Neill 2

This is another can of worms I think - I seem to remember a longish discussion from the archives. I think I got close to the 140 lbs but that is pretty tight. The tab retains the nut so maybe just "tight" is OK.
Bill Bretherton

My view rightly or wrongly is that if BMC have never quoted a torque, even for the later Midgets, it can't be a critical figure. A far as I know there are no figures quoted for the Minor or A30/35 or Riley/Wolseley 1.5 which use the same rear hub. The booklet 'Tuning BMC sports cars' which has comments from Mike Garton, also says 'tight'!!
Bob Beaumont

The ‘works’ spanner, as shown in the WSM, has two handles / arms that may suggest that the nut needs to very tight rather than just tight.
Albeit MGA the excellent MGA Guru website does discuss the similar set up on the MGA.
Alan Anstead

Good point, Alan.

The ‘works’ spanner is double ended. One end for Spridgets, the other for MGA/MGB, although I’m not sure how you’re supposed to measure the torque - as per MGB manual.
Dave O'Neill 2

We use 100+ lb-ft, and grease the nut where it slides over the locktab. Without grease the tab can get dragged by the nut and shear off (or fracture) the tang which engages with the axle.

The nut is quite critical, if it undoes then the whole wheel and halfshaft can work their way out. Happened to our K Midget once, on the track - goodbye wheel. Tang had sheared. So don't rely on the locktab.
Paul Walbran

Thanks to everyone that offered advice, when I undid the nut it was pretty tight so I decided to take Paul W's advice and lubricated the nut and lock washer and did it up to 100 lb-ft.
The old bearing appeared to be in reasonable condition and tapped out quite easily, the outer edge of the bearing had a polished look to it as if it may have been turning a little in the housing. I considered using bearing lock on the new bearing but decided against it as it seemed reasonably snug when tapped back in.
Now to put some miles on it before rechecking.
R.A Davis

This thread was discussed between 11/11/2024 and 16/11/2024

MG Midget and Sprite Technical index

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