[s-cars] Rotor hats and rings

[Eric Phillips]

On 4/15/06, Eric_R_Kissell at whirlpool.com <Eric_R_Kissell at whirlpool.com> wrote:
>
> What does warping have to do with thermal mass?  And would we expect a high
> or a low thermal mass to warp more?

The more thermal stress you put on a metal part, the less likely it is
to return to its original dimensions.  Since the rotor is not just a
flat disk, but a sort of ring on a cylinder, the heat does different
things to different parts.  The ring can expand faster than the
cylinder, leading to "coning."

Thus, a low thermal mass would probably tend to warp more.  Also,
rotors with less-than-ideal metallurgical properties.

> For that matter, what does warping have to do with turning rotors?

A small wave can be taken out by milling both surfaces parallel.  Yes,
less mass will then make warping more likely.

> The best way I have found to correct warped rotors has been to undertake an
> "Itallian tune up" by  achieving a high rate of speed and then braking
> aggressively to near stop several times in a row to get the brake rotors
> very hot and then driving to allow the brakes to cool before stopping
> again.

That might cure issues relating to pad material adhering to the disk,
but if the rotor is truly warped, heating up to "way hot" is not going
to fix it.

>  Thus, I would expect running on a track to be a good way to reduce
> warping unless one ends a track session without cooling down the brakes and
> then they might warp due to uneven cooling off the track.

Track sessions are a good way to overheat and warp stock rotors.

> I am curious regarding the science of warping.  What have people
> experienced?

There are numerous details of the science of brakes and braking on the
web.  Start with StopTech's website, then try bira.org.

Happy braking,
--
Eric

1995 UrS6 "Silber Geist"