Some info on turning rotors:

[phenryiv1]

I searched Google for info on turning rotors (I was unfamiliar with the concept), and this is what I found:

http://www.team3s.com/FAQrotors.htm

From http://www.davefancella.com/in...Drums :Quote »Turning MetalTurning rotors and drums is just the act of shaving the outer layer of metal on the actual friction surface. This requires an expensive brake lathe and is usually beyond the scope of a home mechanics resources. Luckily, most auto parts stores will gladly turn your rotors and drums.

But should you get them turned?

The Great Debate on Rotor TurningFirst, let's examine why we turn rotors. A good brake technician will tell you that we turn rotors so they'll be perfectly vertical against the brake pads. This same good brake technician will also tell you that if the rotor is warped (noticed through a pulsating brake pedal) then it is bad and *must* be replaced. So if my rotor's not warped, then it's already perfectly vertical against the brake pads, right? Then why should I turn the rotor? The good brake technician can't answer that question.

The great brake technician can. He'll tell you that cutting the rotor makes a raw surface available for the new pads, will cause the new pads to generate a bit more heat and will help them to seat properly against the rotor. In the long run this will actually increase the total miles you get out of the brake job. He'll also generally refer to 'turning' the rotor instead as 'resurfacing'. It's important to remember that turning the rotor is actually 'resurfacing the rotor'. You're putting a new surface on the rotor, that's what you're doing.

So should I turn my rotors when I change the pads?

I say 'not usually'. I also say 'sometimes turning the rotor causes more problems than it's trying to solve'. Consider that each time you turn the rotor it gets thinner. Thinner rotors warp easier than thicker rotors, and most people actually drive their cars a little wrong with regard to their brakes, so you want as much metal as possible on your rotor. If you want a more abrasive surface for your pads to seat against, using a heavy grit sandpaper on the surface of the rotor will provide that. Just sand it 'till it's shiny and go with it. Keeping in mind always that resurfacing the rotor is the *best* thing you can do. In fact, if you have the money to do it, go ahead and take your rotors down and get them turned. It's really the 'right way' to do it. I don't, though, because I have a great deal of experience to back up my decision here. Unless you have similar experience to back up that decision for yourself, I really do think you should get them turned instead of taking any chances. The quality of your brake job is going to directly affect the safety of your vehicle, so don't cut corners.[/quote]I posted this as a resource. If anyone has any more information, please feel free to post it here.

[Grant@tirerack]

This is sort of like my wife asking if a pair of slacks makes her look fat. There is no 'correct answer' ,as is obvious from the author's response. Turning the rotor will reduce mass and make it more prone to overheating and warping. The main thing to worry about is the transfer film on the rotor surface. If the rotors are smooth (no lines like an old LP record) and you are using the same pad compound on the new pads, just switch them out. The only time you need to resurface is if:

1) you have excessive wear on the rotor surface

2) you are switching pad compounds

If you are switching pad compounds, you should only need to use some fine grit sand paper or a 'scotchbrite' type abrasive pad to remove the transfer film from the last set of pads. This give you a nice clean surface to build up a new transfer film when you bed in the new pads. If any of the remaining film is left from the old pads, it will hinder the break in of the new pads. When you bed in pads it lays down a thin film of compound on the surface of the rotor. This helps the pad bite and grip as you apply pressure when braking. If the pads are not broken in correctly the film will not evenly cover the rotor surface. When this happens, you will feel a vibration in the steering wheel as the pad grips on the areas of the rotor that have the film and slips on the areas without adequate film. If you feel a pulse through the pedal, you likely have a warped rotor that is pushing against the caliper piston and you'll feel it as you press down. Always follow the pad maker's bed in procedure provided with the pads. It will vary depending on the pad compound.

[phenryiv1]

I have a slight warping, so I was looking into resurfacing. I think that I will just replace them, btu I posted what I found just for a reference. Your additions certainly enhance the utility of the info that I posted.

[Q45tech]

Trueing rotors is half the problem, most hubs on which they mount are warped so you put a good new or trued rotor on a warped hub the rotor soon follows the warp.

Why most dealers have gone to on the car latheing which mis cuts the rotor to follow the hub.

Most don't want to pay for extra services so they end up with half warped rotors leaving the brake job.

OEM has specifications for warps usually less than 0.0028"

[Def]

FYI, brake rotors don't "warp" per say since they are a brittle material. There can be some runout due to the hub, but most of the pulsating people feel when braking is actually pad material transfer to the rotors. This builds up unevenly, and is very prominent to the driver.

If you "warp" a set of rotors, look at your pads before you look at replacing your rotors. EBC Greenstuff pads are notorious for this at moderate street driving, and lots of street pads will do this when overheated on the track.