Rotor warp question

A colleague and I were discussing brakes and rotors the other day and
he said that he keeps two sets of rotors, so that when he replaces his
pads, he can have the second set turned. Then, he swaps the ones that
were recently turned with the ones on the car.

While we were talking, he mentioned that the techs at the auto place
he patrons recommend to not get the rotors turned until they will be
put on the car, otherwise they will warp.

If that is true...what would cause a rotor to warp in a box? Or, why
don't they warp in the auto store awaiting to be purchased?

Just curious.
TIA.

" wrote:
>
> A colleague and I were discussing brakes and rotors the other day and
> he said that he keeps two sets of rotors, so that when he replaces his
> pads, he can have the second set turned. Then, he swaps the ones that
> were recently turned with the ones on the car.
>
> While we were talking, he mentioned that the techs at the auto place
> he patrons recommend to not get the rotors turned until they will be
> put on the car, otherwise they will warp.
>
> If that is true...what would cause a rotor to warp in a box? Or, why
> don't they warp in the auto store awaiting to be purchased?

Maybe it was just a misunderstanding of what was actually said. Consider
this - If you have the rotors turned and wait a couple of years before
installing them, at that point if it turns out a poor job was done
turning the rotors true you are going to have a tough time taking them
back with the complaint 2 years after the work was done.

-jim

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On Jun 2, 6:32 pm, jim > wrote:
If you have the rotors turned and wait a couple of years before
> installing them, at that point if it turns out a poor job was done
> turning the rotors true you are going to have a tough time taking them
> back with the complaint 2 years after the work was done.
>
> -jim

Good point. Thank you.

wrote:
> A colleague and I were discussing brakes and rotors the other day and
> he said that he keeps two sets of rotors, so that when he replaces his
> pads, he can have the second set turned. Then, he swaps the ones that
> were recently turned with the ones on the car.
>
> While we were talking, he mentioned that the techs at the auto place
> he patrons recommend to not get the rotors turned until they will be
> put on the car, otherwise they will warp.
>
> If that is true...what would cause a rotor to warp in a box? Or, why
> don't they warp in the auto store awaiting to be purchased?
>
> Just curious.
> TIA.
>
read this article.
http://www.bendixbrakes.com/download...ury-Rotors.pdf


a)improper storage can lead to warped rotors.

b) A lot of vehicles now require machining the rotors on the car, so
turning them off the car and storing them is pointless because they'll
still have to be machined on the car.

Ray

The problem is not the rotor themselves being warped, but rather the
mating surface is not true. You should always have the rotors turned
while installed on the vehicle, this way you eliminate the
imperfections of the vehicle.


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"ray" > wrote in message
news:GWs8i.260557$6m4.50447@pd7urf1no...

>
> a)improper storage can lead to warped rotors.
>
> b) A lot of vehicles now require machining the rotors on the car, so
> turning them off the car and storing them is pointless because they'll
> still have to be machined on the car.

There probably isn't an on-car lathe in this little town. While on-car
machining may be the quickest way to a true disc, it is not necessarily
the only way.

Most mechanics, I would suspect, never clean the mating surfaces of the
disc to hub, nor do they check the thickness and runout. It takes time,
but more than that, I would guess that many dont recognize the need for
nor importance of doing it.

Old techniques are slow to die out.

wrote:
> "ray" > wrote in message
> news:GWs8i.260557$6m4.50447@pd7urf1no...
>
>> a)improper storage can lead to warped rotors.
>>
>> b) A lot of vehicles now require machining the rotors on the car, so
>> turning them off the car and storing them is pointless because they'll
>> still have to be machined on the car.
>
> There probably isn't an on-car lathe in this little town. While on-car
> machining may be the quickest way to a true disc, it is not necessarily
> the only way.
>
> Most mechanics, I would suspect, never clean the mating surfaces of the
> disc to hub, nor do they check the thickness and runout. It takes time,
> but more than that, I would guess that many dont recognize the need for
> nor importance of doing it.
>
> Old techniques are slow to die out.
>
>

I was thinking about this, and is it because the tolerances for warped
rotors have gone down or ???

My big old american rustbucket beaters never had warped rotors. My
wife's Beretta warps them just sitting in the driveway.

I do sometimes question if new and improved really is new and improved,
and in this case, the "old way" of brake jobs seemed to have resulted in
a lot less problems with warped rotors.

Sometimes "old school" isn't so bad - it's hard to mess up something
that doesn't require precision. I liken it to the difference between
the drawing board (CAD screen) and the real world. On the computer
screen, your "dog-lick" engineering solution looks really sexy, but in
the real world, it fails miserably.

That said, I don't miss carbs. To me, FI is actually simpler to
understand and repair.

Ray

It all has to do with the elimination or asbestos pads. For years, we
as consumers were taught if we heard brake noise we have a problem.
That rule no longer applies with semi-metallic pads. In order to
combat the noise issue, manufactures are making the rotors out of
softer metal. Which in turn makes them more prone to warping. Just
compare rotors from a 04 f150 to a 71 f150.


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