Posted by Alan Bowes on September 28, 1997 at 12:35:53:
In Reply to: Now That's A New One! posted by Pete Kamm on September 28, 1997 at 00:14:06:
: Today I bought new wheels for my '64 W200 crew cab to replace the old split rims. I don't think the wheels had been removed in decades so they fought me all the way. The last one, front drivers side was impossible. I spent half an hour finally resorting to a 3 foot cheater bar to loosen the lug nuts. I'm not a small boy by any means, but even after a full turn on each nut, they still could take all of my weight. Who's the wise guy that made LEFT-HAND THREADS on my wheel?!!
: Does anyone know if thats common? I nearly broke or stripped the lugs before I realized it. I thought I'd seen it all!
: Pete in Golden, CO.
Actually it's kind of an old idea. It's standard on military vehicles (like my M37) and I think also on the WM300. I've also had some other cars with left-hand studs on the left side. The idea is that if you forget to tighten the lugnuts, the forward rolling action will tend to tighten the nuts rather than loosen them. The nuts are tapered where they contact the wheel. If they are loose, the circumference of the part of the nut that contacts the wheel will be slightly smaller than the circumference of the part of the hole that they are contacting. Obviously, when the nuts are tight, the circumferences of the mating surfaces are the same. Anyway, this means that if the nuts are loose and the wheel makes one full revolution forward, the nuts will have to turn slightly more to 'catch up' with it, thus TENDING to tighten them if they have right-hand threads on the right side and left-hand threads on the left side. It may not ALWAYS work, because the taper of the mating surfaces tends to want to push the nuts off of the stud, but perhaps in most cases, they would tend to tighten.
I had an old Studebaker with left-hand studs on the left side of the car, so civilian machines sometimes used this same idea.
Alan
PS: On some military vehicles, all of the hubs are the same, with the exception of the wheel studs. It is not uncommon for a right-hand hub to be installed on the left side of a vehicle, or vice-versa, so it's a good idea to always check the threads before using a wrench. Sometimes the studs are marked with an L on the end, but not always.