CDF Discussion, post Team Update 14

[GeeTwo]

Originally Posted by Retired Starman

When I first read your post, what came to mind was, "Wonder if this is on a four-wheel drive vehicle"?

No, it was a rear wheel drive 1991 Cherokee.

I did a bit of online research, and it appears that the more likely problem for the wheel was loose nuts. Left side nuts tend to loosen farther and spin off, where right side nuts just don't provide enough contact force and put lots of shock force on the studs. While I don't have those studs anymore (though I did find one after I pulled off the road), they had the "beach" look on the sheared face.

As to aluminum, I did find several claims that aluminum wheels were more likely to have this issue than steel, but they were anecdotal or otherwise suspect. Admittedly anecdotal, but I noticed that a few of the aluminum wheels which were thrown happened in snow or had plants without foliage in the background. As aluminum has a higher coefficient of thermal expansion than steel, it seems reasonable that a lug nut tightened on a steel stud against an aluminum wheel in warm weather (or a warm garage) would loosen in cold weather.

I also found quite a few recommendations to re-torque lug nuts after a dozen to a hundred miles after they're removed/replaced. If the nut was tightened a bit off-center, jostling can loosen them. This is essentially the same reason I often stop about two miles down the road and check cargo straps.