What could be the cause of damaged wheel nut surfaces on aluminum rim?

Question

I recently managed to damage the rear right door area of my car, including minor cosmetic damage to my rear right rim, and got a new rear rim paid by insurance.

Today was the time for seasonal wheel change (from summer to winter wheels). During the trip to wheel change, I noticed a feeling similar to low tire pressure. I suspected the cause could be either freezing temperature dropping pressure on all 4 tires, or the replaced rim having a slow leak.

When replacing the wheel with the new rim, I noticed that only one nut required a cheater bar and Gorilla-like force. The rest of the four actually had a reasonable torque. Usually my experience has been that if a wheel has been installed by a shop, all five nuts require lots of swearing to untighten -- this time, only one did.

Also, I noticed one of the nuts (not the overtightened nut) didn't spin completely freely for the first few revolutions, something was "braking" it, but after few revolutions of using a wrench, it started to spin freely.

I checked the nut and the corresponding bolt permanently fixed to the wheel hub, and neither had any damage. Then I checked the rim, and was shocked to find this:

That wasn't the only damage. There was also another damaged surface, that however didn't act as a "brake" for a spinning nut so it was far less severe:

My question isn't about whether I should get them replaced (I already sent an inquiry to the dealer from which I got the new rim). My question also isn't about the safety of these rims (the fact that I suspected tire pressure loss and later found every single tire to have exactly the same good pressure already demonstrates the rim may be unsafe, and if tire health questions are off-topic then perhaps rim health question should be, right?).

The question is: what could cause such damage? I have done seasonal wheel changes using aluminum rims for the last 11 years. Not a single time have I managed to install a wheel in such a manner to cause damage like this. Is the rim material defective (too soft aluminum)? Or incorrectly installed by the dealer? If incorrectly installed, how on Earth could they manage to install it in such a manner to cause the massive damage on nut surfaces?

Not a single one of the nuts was loose -- although the torque wrench I had works only one one direction so this was just a general untightening feeling rather than a scientifically accurately measured torque: 4 torqued just fine and 1 torqued probably with an impact wrench to several times the torque spec. Could it be caused by uneven torque -- 4 about right, 1 massively overtorqued?

Answer 1

Ok, now I have a replacement rim for free. The shop assessed that the damage isn't a hazard to traffic safety, the rim can still be used, but since this might affect the resale value of the car, I opted to have a new rim for free.

The shop also suspected that the rim wasn't perfectly seated and therefore only one nut was perfectly tight. Probably the remaining four had inadequate torque (the rim could have moved slightly after installation when driving the car, so the remaining four had reduced torque after this movement), but my hand is not a precision torque wrench so this is very hard to assess.

Also from this point on, I will always post-tighten all lug nuts after 50-100 kilometers of driving. Not sure if this is what caused the damage, but better to check than to not check.

It's slightly annoying that nearly all shops use impact wrenches. My opinion is that it would be much better to use an ordinary cordless drill with low torque setting, and then add the rest of the torque using a torque wrench.

Answer 2

Tire pressure: Air change the pressure by the temperature. If the tires were inflated on for example 60F days, at 40 PSI, they could be easy at 34 or less on a 30F or less temperatures.

Even if the day was cold when you inflated them , sometimes tire shops have their compressor running all day and the air in it is warm/hot. and get to the tires hot and the pressure is different when you go out and use the car and the air gets cold. That's way some shops offer nitrogen filled tires. Nitrogen is not affected as much as air by the temperature. Same happens with air suspensions, like the jeep, the internal system is filled with nitrogen, so it wont change the pressure at different temperatures.

About the nut. Its very important that you tighten all nuts by hand all the way down, before start the tightening by tool. Is provable that the wheel wasn't sit completely flat over the hub or the bolt/nut wasnt centered and bite the side of the wheel, and you tighten that bolt/nut first. so the other bolts/nuts did the pressure and corrected the wheel but giving that first bolt/nut way more pressure.

Also bolts/nuts must be adjusted in cross pattern.

That mark on your rim wont affect the bolt/nut but if you care a lot about your wheels you can get nuts/bolts where the concave part is a separate moving piece (like a washer), so that will sit on your rim and the nut/bolt will rotate over that, not the rim. so you avoid marking them and that helps to center the nut/bolt too.

Somehow, this nuts/bolts are pretty common in the rest of the world but not much here in the us.