Do Brake Rotors Warp

shotgunslade · #1 08-26-2006, 09:16 AM

The Answer is: Yes. Just got an opportunity to take my wheels off and look at the brakes since my track day. Brakes have been making grinding noises and vibration since I got back from the track. Thought I might have ground the pads down.

But.... Plenty of pad left. Smear around the front rotor at mid span is rust, not melted pad stuff. Essentially, the rotor has warped such that there is a depression running around the rotor midway between the hat and the edge of the rotor. That region is not being wiped by the pad, so rust is left.

These are Bien's drilled and slotted and have never given me any problem before. Pads are Axxis Ultimate.

Where to go from here? Have a track day at Watkins Glen September 18, so time is of the essence. Clearly, I'm at the point of putting way too much stress on the brakes for even drilled and slotted to avoid warpage. Have reviewed previous posts, especially from Paisan, who used to be an SVX track-day person, now 94 Turbo LGT, and who was my instructor at a recent SCCA event. He recommends slotted strongly, but advises against drilled. Have an e-mail in to Frozen Rotors, looking for cryo-treated slotted brake rotors. Think maybe cryo treatment is a strategy to avoid warping.

If any of my fellow SVX-net members have their secret big brake solutions ready for beta testing in the next 2 weeks, sign me up. Need to get something by Friday, September 15, so can insall that weekend. Will keep all posted, Welcome any suggestions.

Suby Fan · #2 08-26-2006, 09:18 AM

get them turned

Manarius · #3 08-26-2006, 09:38 AM

Cross Drilled have more tendency to warp. The holes weaken the overall structure of the disk. Larger vented ones (and/or slotted) would be far less likely to warp.

shotgunslade · #4 08-26-2006, 10:15 AM

Shop refused to turn drilled and slotted rotors. Am getting new slotted only.

ensteele · #5 08-26-2006, 12:15 PM

Be sure to torque them to the proper ft lbs. That will help and is a factor on the stock ones when they warp.

Suby Fan · #6 08-26-2006, 01:15 PM

Quote:

Originally Posted by shotgunslade

Shop refused to turn drilled and slotted rotors. Am getting new slotted only.

there is a risk of getting the bit caught in the holes but you should be able to find a shop that will do it... i do it... you just cant cut more then .02" off at a time

shotgunslade · #7 08-26-2006, 01:31 PM

Earl:

Was reading some previous posts about warped rotors, and saw the issue of lug torquing several times. Went out to check my lugs and they were on way too tight. For whatever reason, I forgot to check them the last time I went to the track, and I guess the shop that did my last pre-event tech inspection put them back on with an air-wrench. Came back in and saw your post mentioning this issue. Will definitely remember always to check the tightness of the lug-nuts after I take it to the shop, no matter what the reason.

SVXRide · #8 08-26-2006, 09:04 PM

Dan,
I never use an air gun to tighten the lugs on my race or street rims. I use a torque wrench at take them to 40 ft-lbs, then up to 85 ft lbs. I'm using the AXXIS pads with Raceconcepts' dimple drilled and slotted rotors and SS lines -- no issues with warping after a couple of seasons' of autoX use. Given your "track" use, I think going the cryo-treated route is a good one. Have you talked to "old Tom" yet about his "big brake" set up?
-Bill

shotgunslade · #9 08-26-2006, 10:13 PM

Bill:
I feel really stupid about the lug tightness. I don't use pneumatic tools to tighten the lugs, either. I got my tech inspection on Thursday, before I went to the track on Friday, and had been travelling earlier in the week, so re-tightening the lugs to the correct torque setting was an agenda item that sort of fell off the table.

I have talked to Tom about his big front brake mod, and I plan to install it when he makes the adapter plate available. In the mean-time, I have asked for quotes from ART and Frozen Rotors. I really like the look of the S P Performance diamnond slotted rotors, though, I have asked ART if they would cryo-treat those rotors.

I need a fix for this by September 18, when I am going to Watkins Glen.

oab_au · #10 08-27-2006, 01:37 AM

Quote:

Originally Posted by shotgunslade

But.... Plenty of pad left. Smear around the front rotor at mid span is rust, not melted pad stuff. Essentially, the rotor has warped such that there is a depression running around the rotor midway between the hat and the edge of the rotor. That region is not being wiped by the pad, so rust is left.

Welcome any suggestions.

Dan this mark around the disk, is it;

On both, of the front disks?
Is the mark the same, on the other side of the disk. Or the opposite, with the edges rusty and the center shinny?

A photo shot would be great.

Harvey.

shotgunslade · #11 08-27-2006, 09:45 AM

Harvey:

The patterns are the same. By the way, for those who are buying zinc plated rotors, these are about 2 years old, and, as you can see, the hat is rusted, as are the drill holes and the rotor edges. Not pretty.

oab_au · #12 08-27-2006, 06:09 PM

I'd like to see the pads and how the drilled holes line up with the cast vents, But it certainly looks like it is caused by the drilling of holes through the disc.

Vented discs should not be drilled, as it interferes with the way the air flows through the vents, to cool the disc. The air should enter the vents in the center of the disc, to flow through the vents, to exit at the outer edge, due to the centrifugal force generated.
When holes are drilled through these vents, the centrifugal force will cause the air to enter the drilled holes, and flow out the edge, to short circuit the vents flow. This will cause the disc to cool at the outer edge, but overheat in the center, as the air is not flowing through this area.

Harvey.

shotgunslade · #13 08-27-2006, 06:21 PM

Harvey:

Probably so, but these are the same RaceConcepts rotors that many people on SVX-net have. My next set of rotors will slotted but not drilled, maybe dimpled. In any event, I'm going to make a decision tomorrow, whether or not to get new front rotors, right away. I'll probably go out and try the home rotor turn on the expressway first. I know that sometime in the future, I will have new big front rotors courtesy of another SVX-net member, but don't know when that will be. If that is the case, I'll probably go inexpensive for the new rotors. On the other hand, I'm waiting for a quote from Frozen Rotors to see what their cryo-treated rotors cost, and to see if they have slotted and dimpled. Might be able to use them for a while, then sell them to another net member.

Just want to make sure the diagnosis is correct. Definitely warped. Probably because of too tight lugs and an overly active track day.

SVXRide · #14 08-27-2006, 07:49 PM

Dan,
I've got two sets of the RaceConcepts dimple drilled and slotted rotors - purchased before Wood sold the company. I didn't know they even sold drilled versions like the ones on your car.
-Bill

immortal_suby · #15 08-27-2006, 07:52 PM

Quote:

Originally Posted by shotgunslade

Harvey:

The patterns are the same. By the way, for those who are buying zinc plated rotors, these are about 2 years old, and, as you can see, the hat is rusted, as are the drill holes and the rotor edges. Not pretty.

wow those look like ****.
my ebay cryo treated slotted bradis still look good after about 4 years but I guess part of it is due to no salt down here.