Are you supposed to torque locking lug nut to the same spec as other lug nuts?

[Michael]

My truck (Silverado 2008 LT1500) has 22mm lug nuts that supposed to be torqued to 140 ft*lb. Each wheel also has a locking lug nut and it doesn’t look very robust… I am afraid applying 140ftlb will strip it. Also, locking lug nut key takes smaller size sockets… Yes, it has two surfaces that fit 19mm and 21mm sockets (I think). Applying same torque to differently sized nut should produce different force, isn’t it?

I expect that applying 140ftlb to 19mm nut is equivalent of applying 140 * 22 / 19 = 162.10 ftlbs to 22m nut. Following this logic I am supposed to apply ~120ftlb to my locking lug nut, but even then I am still worried about stripping it…

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[Bill]

If they are the correct wheel locks for your truck you should be able to torque them to the same torque as the other nuts.

[Michael]

Yes, I’ve realized mistake in my logic — required torque is a function of bolt/stud diameter, not size of it’s head. I.e. it doesn’t matter which size your lug nut is — you still have to apply 140ft*lb of torque.

The difference is that this torque will generate:
– ~1940lb of force applied at one side of 22mm nut or ~323lb for each side (I assume it gets evenly divided between all 6 sides)
– ~2245lb for 19mm bolt (~374 per side, assuming 6 sides)

this force will translate into force applied by lug nut on the stud and (since ratio will be different) — we will end up with the same force applied to the threads. My bad, didn’t think it through…

Surface profile where key meets the locking stud looks too delicate, too shallow and has quite small diameter (around 16mm maybe). This got me worried… I’ll report if I run into a trouble.

Edit: I think, forces above need to be doubled — gotta use nut radius, not diameter (i.e. for 22mm nut shoulder ratio is 11mm:1ft, or 1:27.71. I.e. 140lb of force at 1′ is equivalent to 3879.4lb at 11mm, 646.6lb per side).

[Michael]

Huh… I couldn’t tighten my locking lug nuts to 140 ftlb. Unlike other lug nuts (which click after 1-2 crank on a handle) these were cranking and cranking and cranking… wrench never clicked. I wasn’t comfortable to keep pushing it — it felt like smth is getting stripped somewhere. Grooves look a bit stripped — looks like someone had problems with them before (they also weren’t really tight when I was loosening them). I’ll probably simply replace them with normal lug nuts.

Attached pic just in case.

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