I had a new front upper control arm installed last week, and when I took the car out afterwards I could tell things weren't quite right. The balance, that had been fine, felt a little off. And the braking, which was very smooth before, now had a slight vibration.
We have thin rotors. And even though I have brand-new Brembos on the front and back, they're still sensitive to overtightening of the lug nuts. What I think happened was the shop put the left front wheel back on, didn't hand-tighten the lug nuts while holding the wheel in place (to get it centered exactly), then hit it with the air wrench and over-tightened the lugs. Not by much, but I could tell when I took them off that the amount of force to break them loose was higher than normal, I'd say by 20%.
Anyway, by loosening up and retightening the lugs to spec, the problem disappeared. Moral of the story: if you are having problems with balance or vibrations during braking, particularly after a wheel has been put back on, retighten those lugs yourself, and make sure the original set of the wheel on the lugs is centered well.
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