Because the nuts/spinners are handed they *won't* go back on the wrong side
of the car - unless you really really try. I'm assuming you didn't get the
hubs off, this *would* allow the nuts to go back on the wrong sides. The
right-hand side of the car should have left-hand threads and vice-versa, so
the normal forward rotation of the wheel (both sides) tends to tighten the
nut if held stationary. Most are also marked in some way to indicate either
which side they should be fitted or the direction of forward rotation.
Centre-lock wheels are self-tightening (in the forwards direction) so if the
threads are correct for the sides the only way a wheel should be loose after
a very short distance is perhaps if it hadn't been fitted correctly and
fully tightened to begin with. They *will* come loose if driven or towed in
reverse for a significant distance.
----- Original Message -----
> Well, I didn't realize this. I pulled off all 4 wheels, cleaned and
> them, mounted new tires, and put them back on. No way for me to know
> wheel and which nut came off of which side of the car.