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MG Midget and Sprite Technical - Torque for bolts that connect disk to hub?

I have a 73 midget with wire wheels.
I am changing my front disks. I bought new Moss Motors disks (cheap ones from China I think). I could not find the torque for the 4 bolts in the workshop manual but I did find two places in my Haynes manual where it said it was 43 ft/lbs. So that is the number that I used.

However, on the first disk one of the holes stripped out. This number really seems to high for this size bolt. Also, since this bolt will get mostly shearing force it does not even seem that it needs to be very tight. It seems to me that 30-35 ft/lbs would be fine.

What do people recommend?

Also, I have read conflicting numbers for the castle nut torque (and it seems to make a difference if it is wire wheel or not). What torque should it be?

Thanks,
Rebecca
R Harvey

never used a torquewrench for those
just make sure it is tight and does not strip the thread.
Onno Könemann

the BL workshop manual says 40 to 45 lb ft for the disc-to-hub nuts; for the main hub castle nut it says 45 lb ft and then tighten to the next split pin hole.
David Smith

I torqued it to 43 and stripped one of the holes so clearly either that does not apply to cheap junk from China, it was defective, or it is just wrong. Moss did say that they would take the disk back.

I think that I will just hand tighten it as suggested by Onno.

I prefer to use a torque wrench but I don't want to repeat the same mistake. It seems to me that for this type of part where the force is going to be a shearing force that it just needs to be tight enough to not come loose.

Thanks for your suggestions.
Rebecca
R Harvey

I should add that since I am talking about wire wheel disks it is not nuts. I am torquing the hex head bolts.
Rebecca
R Harvey

I agree that using a torque wrench is best, just to be consistent really.

If there is no torque value in the book, then use the industry standard for that size of bolt. If at that torque it stripped, then it was a bad rotor, and I wouldn't trust them. Have Moss refund you for them, and then get some good ones somewhere else (if the one part was defective, why would any of the other ones be any good / trustworthy (warp, crack, other), even if they don't strip during assembly?).


Norm
Norm Kerr

The disc to hub bolts are high tensile and 45 lbf. ft. is the correct torque for them. The disc is clamped to the hub by the bolts and it is the friction generated by the clamping force between the disc and the hub that prevents movement, not the bolts resisting movement in shear. They do need to be taken into their 'elastic' range, but not beyond, to work as designed.

Richard
Richard Wale

This thread was discussed between 21/05/2010 and 23/05/2010

MG Midget and Sprite Technical index

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