This might seem like a stupid question, but when do you turn the rotors. Is it every time you change the pads? I'm changing my pads right now and my rotors seem VERY smooth and was wondering if I still need to? Thanks in advance.
If the rotor is NOT warped, then the LAST thing you wanna do is REMOVE rotor material! Instead, just put a non-directional surface on the rotor (I use a drill with a small circular sanding pad on it) and then bed in your brakes properly.
If the rotors ARE warped, replace them. Turning them just removes material and makes them MORE likely to warp/crack in the future (meaning you'd not only spend the money to have them turned, but ALSO have to spend the money to replace them shortly after....like you should have done in the first place). Our rotors are cheap enough that I'd consider them throwaway items if they are damaged in any way.
Also be sure that all other brake hardware (lines, bleed screws, slide pins, etc) is serviced properly and in good shape while you're in there. And a re-bleed of the brakes (especially if the fluid is more than a year or so old) is highly recommended as well.
If you're rotors have less than 1/16" grooves, there's definitely no need to turn them. Although I respect Ed's opinion, I have a little different view on turning them. I hate to throw away something that still has some life left in it. (Partly because that's just the way I am, and partly because I'm always broke! )There is a minimum service thickness every rotor has. Even after turning them, they may still have much more meat on them than the min required. I've always been able to turn them at least once, but if they're going to be anywhere near the min I'll buy new ones. JMO.
Even if they had deep grooves, I still would never turn them. I would either run them as is or replace them depending on the depth of the groove and how much thickness is left in the rotor. You just loose too much material trying to get rid of the groove.
I know someone who periodically removes the pad and knocks out the raised portion of the pad to even the rotor out over time. I don't know if that's worth the trouble, but he says that it works for him.
I was told the same about cutting rotors. If they don't need, don't do it. My 12 yr old pickup with 180k miles has never had the front rotors cut....just pads replaced every 25-35k miles. No vibrations or pulsing yet.
Lots of the on forum vendors stock the "powerslot" rotors for our cars, I recommend them over drilled, drilled is bad, it can make the rotor very prone to cracking. I don't like turning the rotors, but if you only need to remove a VERY small amount of material then turning them isn't too bad.
With a lighter car, I see turning the rotors as a better oprion, however, our cars are VERY heavy. All the kinetic energy of the car moving is turned into heat energy by the brakes, thats how we stop. When you turn the rotors, they have a lot less metal to them. What this means is they still have to convert the same amount of energy, but there is less metal to hold the heat energy in. As a result, it gets more concentrated in a smaller space and makes the metal hotter and more prone to warping quickly.
Last time I had a pair of tires mounted, an older gentleman came into the shop I was at and complained, he said "that has to be the worst brake job ever, I got 100 yards down the street and the brake pedal is vibrating like crazy". The man behind the counter explained that they turned the rotors and they were within spec, but they must have been too close to out of spec and they couldn't handle the heat of stopping from 30-35 mph once or twice without warping badly. The shop replaced the rotors for free because they should have known not to take them that close to out of spec, but it just goes to show you. That wasn't in a B-Body, but brakes work the same in all cars...they convert to heat energy, and they do their best to shed that heat from the rotor...when they hold more heat than they can shed to the air properly, they begin to warp. It is a bigger issue with heavier cars, and our cars are some of the heaviest out there.
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