Do I need to "turn" the rotors...

[Illumiloti]

When putting on new pads?

[MattG]

I think you'll find a lot of different opinions out there, but in my opinion, NO, do NOT turn them. However, be careful when the pads are new as it will take some time for them to wear away enough to perfectly match the subtle grooves in your rotors and provide the maximum stopping power.

[tesprit]

Generally, you don't need to resurface your rotors unless they have deep scoring or wear. If you decide not to turn them, it doesn't hurt to uniformly scuff up the friction surfaces so the new brake pads can bed in faster and more smoothly.

[Illumiloti]

will it hurt to turn them. At my last track day I went through the pads of the front left completely, metal to metal. Allen (formerly of Lotus Bev Hills) was there and though chewed up, he didn't think the rotor was ruined. We put on a used pad that Brent gave me to get me home to LA from Vegas. It makes a hell of a racket but I'm hoping it's just because of the used pad against my slightly chewed rotor. I'd like to turn at least that rotor to clean it up. Can I turn just one rotor?

[TimMullen]

Originally Posted by Pestodude

I'd like to turn at least that rotor to clean it up. Can I turn just one rotor?

It doesn't hurt to turn a rotor, but it reduces the thickness and will "wear them out" quicker (and there is a minimum thickness that you can reach fairly quickly). The disadvantage of not turning a rotor is that it will take a bit longer to bed in the brakes. I'll trade life of a relatively expensive part for a bit of careful braking for a bit.

As for turning only one, no. You should always match brakes from side to side so that things are balanced. Change pads one one side, do it for both. Turn or replace one rotor, do it for both.

If you only turn one side, the rotor on that side will be slightly thinner than the other side. That will change it's heating and cooling capabilities (and therefore the braking) from that side to the other.

[Illumiloti]

Great advise, thanks.

[Randy Chase]

No...not because you put on new pads.

Unless you chewed up the rotors.

Oh wait... you did.

So maybe. Depends on how bad the scoring is.

[Slipstreamer]

Only on deep scouring should you have it resurfaced...or you could buy a new pair of rotors....

[xtn]

And...

#1. Check all of your pads prior to every track day.
#2. Don't begin a track day if any pad is less than 50% remaining thickness at it's thinnest point.

xtn

[Illumiloti]

Yeah, my bad. I had checked them but it was a two day event (Lotus Challenge Series) with some very long straights and a lot of track time. I didn't check the pads the second day and I should have.

[Composites]

On race cars, this never works. Every time we turned a rotor from a race car, the rotor quickly returned to being warped, (like two laps). It's as if the rotor develops a memory from the heat generated and machining it fixes the problem until extreme heat is reintroduced. Good for mild street use, bad for race conditions.

Rotors are not that expensive to replace, are they?

[lwein]

I remember being told not to turn rotors,but to have them ground,like a flywheel. Costs more,but take off less than a typical brake machine turning proceedure at a local tire and brake shop.
And as far as I am concerned,the rotors(discs) are that expensive to replace. I am hoping that the S240 discs can be replaced without having to buy the new units,(ie) only replacing the disc,not the hat. Possible with a generic part from Brembo? And a great torque wrench.

[Bleu Omdurman]

It is probably common sense, but...

I change my pads out at about 50% or the end of the track day that gets them there. Then I have fresh pads on the car that I can bed in at the next event. I put the old pads, that are at about 50% in box that the new ones came in and put them back in my track kit. That way I always have a free set of pads laying around in case I or someone else needs them.

It seems kinda odd to have three sets of pads (one on the car, one 50% in the box, and a brand new set in the wrapping), but I have found it is very helpful.

[cruzin2]

Each manufacturer will list what is the minimum thickness of the rotor either before or after turning them. This thresshold should not be breached even for road use, let alone track stuff. My recommendation is... when you have deep groves in the rotors, consider changing them out. You should be able to get a few sets of pads on a single set of rotors depending on usage conditions. More at a track then on the road. On the road, pads tend to wear more closely to rotor wear. Track seems to burn up pads quicker. If you find yourself using pads too quickly on the track, consider a more aggressive pad. You may be putting more heat (higher temp) in them then they were designed for which can remove pad material quickly. (When I went from a larger track with spaced out high speed stop zones to a smaller track where you were on the brakes constantly, we had to change pads or see significant wear. )