turning brake rotor or not?
 

I know most of us here do not recommend turning the brake rotor on FDs. If you can have them turned for free, would you do it?

Anyone know how much is lathed off when they turn the rotors?

I don't have any vibration or squealing with my rotors now. I am not planning on turning the rotor unless you guys think I should.

You can turn them if you want but your brakes will be back to vibrating again withing a few thousand miles. Less metal means less resistance to heat. That equates to more warping and sooner this time. I never turn brake rotors because the cars I drive and my driving style is hard on them as it is. My suggestion is do it right the first time. get a set of Cross drilled or slotted rotors and some good EBC green or Hawk HPS pads to go with em and make sure you have new fluid where your 8 year old fluid was. You will be much happier and your brakes will actually last and grab like a sports cars brakes should. Of course you could half ass it like most americans and pretty much get what you paid for. I saw a set of Brembro stock replacemtn rotors on Ebay for cheaper than a new set of stockers. ALso Tire rack carries Hawk pads for 40 bucks a pair. Good luck

no
 

Don't recommend it....use them until they are toast then upgrade..

If your brakes are not pulsating, there is no reason to turn the rotors. Rotors are turned (machined) to correct the warpage from heat. If they're not warped, there is no reason to turn them.

(The only truly accurate way to find out if a rotor is warped is to run a dial indicator on it.)

If you're putting new brake pads in your calipers, you may want to resurface your rotors. That's basically roughing them up with a 3M pad. Any competent brake shop can put such a non-directional finish on them for you.


BTW, I just read about a recently published study of rotor warpage. It was commonly thought that almost any kind of extreme brake heat could warp rotors, but this study pinned it down much more precisely. It said, in road cars, most warpage is caused by stop lights and stop signs.

When you brake hard from high speed, a very hot plasma gas builds up between the brake pad and the surface of the rotors.
(The function of drilled or slotted rotors is to help dissipate this gas.) When you come to a stop, the brake pad holds in the heat on one spot on the rotor while the rest of the disc cools. The metal on the rest of the disc contracts, while the hot spot stays expanded, and the result is warpage.

If I had to, I woudl turn rear rotors but never the front becasue of reasons mentioned previously. However, since I can't turn rotors myself, putting new ones on is almost as expensive.

I had my rotors turned by a TRUSTED machine shop and have had absolutely no problem with them. It got rid of the pulsation I was having. I think if you are racing the new high performance rotors and pads might be called for, but for general use there is not a reason in the world you can't have them turned and save major $$$. Just make sure you break the new pads in gently for the first 50 miles or so. Rubbing some graphite dust on the newly machined rotor surface also helps the break in process. Don't forget to repack your wheel bearings while you are at it, and new fluid is always a good idea every few years. The stock FD brake system is phenomenal, and you would be hard pressed to do better unless you are willing to spend thousands of dollars on upgrades. (the new M2 system is awesome, I'm sure....)

Miller's post reminded me of a few other things.

Every manufacturer sets specs for the minimum thickness of rotors
beyond which the rotors cannot be machined. (I don't know the FD spec off the top of my head.) That means the manufacturer says it's ok to grind the rotors, so long as the machining doesn't take them below the minimum spec.

The other point regards breaking the pads in. New pads are treated with a chemical to bind the pad material. This chemical has to be bled out gradually. If you get new pads too hot right away you will end up glazing your rotors, and then they will have to be resurfaced.

Moderate braking for the first 50 or so applications should do the trick and seat your pads in properly. Naturally, make a panic stop if you have to. But going out and jamming on the brakes, and doing several full on stops to see how good your new brakes work will end up glazing your rotors and hurting your braking capabillity.