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Locknut - rear wire wheel - torque spec?

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SteveHall64Healey

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Can anyone shed light on the locknuts which hold the rear hub extensions in place (for wire wheels) ?There are 5 on each side, and they are made of a metal that is softer than steel (maybe to bridge dissimilar metals without corrosion?) and have what appears to be slits cut radially into the shanks. Moss part number 031-294.

They look like they might crush when installed. Is there anything special about installing them and does anyone know the correct torque for these nuts?

thanks
steve
 
They're called 'prevailing torque nuts.' Nothing special for install, except make sure the threads are clean so you get an accurate torque reading. Tighten in a star pattern, like you would lug nuts. I believe the spec is usually given dry, decrease a little if you oil the threads. Nominal for 7/16" studs is 75lb-ft, I've always cranked them to 100 (barely perceptible movement from 75). I've also reused them many times with a little blue threadlocker, which IMO is at least as effective as mechanical means. 140K miles or so with no issues.
 
IMO Bob is correct about using the blue threadlocker (loctite). IMO using anti-sieze on them is not a good idea as you want them to stay in place. The anti-sieze is working against what you want to do.
 
steveg said:
IMO Bob is correct about using the blue threadlocker (loctite). IMO using anti-sieze on them is not a good idea as you want them to stay in place. The anti-sieze is working against what you want to do.
Click to expand...

I'm actually schizophrenic about this; I used anti-seize for years with no issues, using a little less torque as Randy suggested. If I reuse a torque nut I usually use threadlocker--clean the anti-seize off first--with more torque, as threadlocker has less lubricity. The idea is the strength of a fastener is from the stretch, and clamping power, of the bolt, not the friction, or lack of, of the threads. But, threadlocker has worked well for me in other places, like front shock bolts, and I use it and lockwashers on things like driveshaft yoke bolts. FWIW, I've never had a failure using any of these methods.
 
For more information, go to trojansf.co.uk. In their products section select "all metal prevailing torque nuts" and scroll down to the photos. You will see the nuts used on the Healey.
 
No anti seize, no thread locker, a good tighten as per an ordinary wheel nut is all I give them and I have not had any issues over the years.

:cheers:

Bob
 
My 100 has a spiral bevel axle with four stud hubs but I have modified the hubs and fitted hypoid axle press-in studs. Being a bit paranoid about thes studs myself, but finding no specified torque figure I tightened mine to 60 lbs/ft. I figured an even tension was as important as the actual torque.
 
Recommended torque values are all over the place, but here's a credible source (for bolts; I'm presuming studs would be the same):

https://www.engineershandbook.com/Tables/torque.htm

I have pamphlets that came with my torque wrenches--I have three, for different ranges--and IIRC they pretty much agree with this, but have different values for dry or lubed. My tire shop always torques my Mustangs lug nuts to 100lb-ft, but they might be 1/2". 100lb-ft is on the high side, but I've never snapped one in over 200K miles on my BJ8. Of course, even distribution is critical, as are clean threads and surfaces, but it seems anywhere from 60lb-ft to 90 or better works.
 
That table is a great resource - thanks.

I went with 75 ft-lbs, dry with blue thread locker on these bolts. So far, so good.

steve
 
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The nuts are self-locking and should not be re-used too many times. I did that and had all five nuts on the left rear loosen during a trip. Before I realized what was happening, the movement of the hub on the studs necked down the threads. When I replaced the studs, I had the old ones tested at the materials laboratory at work and learned that they are Rockwell C32 - C33 hardness (equivalent to Grade 8). The max torque specified in standard torque tables for a Grade 8 7/16-20 bolt is 78 lb-ft. I torqued my new nuts to 70 lb-ft and marked them with "witness marks" to indicate if the nuts were moving and losing torque. None of them ever did. Loc-Tite is not necessary, nor antiseize.
 
This is really helpful Steve. I’ve been cautious about re-using the nuts too many times as well. The current set (not cheap!) have only been torqued into place twice now. The previous set were rounding off at anything approaching 70 ft-lbs, so were replaced. The quantum of contact area between nut and socket in situ is low, making round-off relatively easy.
 
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