Turning down slotted rotors??

I pushed it a bit too far on my Endless SSS pads at my last track day of the season and ran them into the backing plate on my DBA 4000 slotted rotors. The rotors are scored, although not horribly, (they stop just fine with my Carbotech Bobcat street pads on). I had planned to get them turned down a little to true them back up but after thinking about the fact that they are slotted, maybe you can't turn them down? After calling the Firestone that does my brake/alignment work they confirmed this. They told me that while some shops might offer the service, that is a dodgy process at best, it tears up the heads used to turn the rotor down and never really cut consistently due to the slotted design. Makes sense to me, has anyone ever turned down their slotted rotors? If this is the case, I think from now on I'll run non slotted in the future, these are too damn expensive to just chuck in the garbage...

You can have them turned.

Yup. I messed up slotted rotors in exactly same circumstances.

 

I was told by teh manufacturer that all excuses given by shops are BS. I had them turned at a local NAPA (they charged me double ). They came out fine, except they took way too much material. While still in spec, not much life is left in them.

Gotcha. I emailed Eric at Brakeswap.com today, (he's a frequent post provider on this site), and asked him about my situation. Thankfully he got right back to me within the day and allayed my fears a bit. Along with a picture that he included showing both "acceptable cracks" and "cracks requiring replacement" he told me this:

 

"The little cracks in the following picture are "normal" and are caused be repetitive heating/cooling deltas. When one of those cracks extends to an edge like the middle top of the picture, then people throw em away."

 

Comparing my situation to his picture, I feel really confident that I'm ok to run these some more. I have no cracks nearly as large as what I saw in the picture and none of them extend out to the edge of the rotor, (which definitely means it should be replaced). In fact, the "cracks" are so hairline, so minutely fine that I think I'm good to go some more miles.

I know, back from the dead. But I did a search before I made a new thread.

 

In another thread I mentioned I had my slotted rotors turned. A couple of members questioned how that can be done. They were told they can be turned.

 

Today I finally had time to ask my buddy who owns the machine shop how he does it. He said he uses the flywheel grinder. They were finding that some of the cheaper rotors would not turn true. So he started useing the flywheel grinder. So he began using it more and more. It also gives the rotors a nice surface for the bits to bite into.

 

If you think about the brake rotor turner, all it dose is put threads into the rotor surface. The grinder doesn't do that.

You can surface them on a mill pretty easily as well, and they'll be true to the hat. You can also do it on a lathe if you know what you are doing.