On Fri, 19 Jul 2002, James Wetzel wrote:

> To all the experts out there:
>
> Does over-torquing lug nuts lead to premature rotor warp?  I have seen this
> debate rage among brake experts.  One the one side, some say that only
> excessive heat, i.e., braking hard for quick stops over time leads to rotor
> warp.  Others say it is the air-gun jockey with no torque sticks that lead
> to it.  I think it is a combination of both.

There's a *lot* of discussion of this on rec.autos.makers.honda.  Modern
cars have been shipping with thinner and thinner brake rotors, as a way of
saving weight and improving EPA fuel economy numbers.

I've also heard a theory that it's caused by sitting with your foot on
the brake after heavy braking.  (The theory being that the rotor cools
differently where it's clamped by the caliper.)  Personally, the only
warped rotor I've had was done in by a draggy caliper, so heating was
definately the culprit there.

It seems logical to me that it'd be a combination -- maybe the
over-torquing (actually, I'd expect uneven torquing to be more of a
culprit) sets up uneven stresses in the rotor, then the heating/cooling
cycles allow it to permanently deform in response to those stresses.

             _ _
  __ _ _   _| | |  | David M. Brodbeck (N8SRE)              Ypsilanti, MI
 / _` | | | | | |  +-----------------------------------------------------
| (_| | |_| | | | @ cyberspace.org
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