Disc rotor damage?

[onegymrat]

Found these small burn marks on my rear rotor during my usual post-ride clean-up. Wasn't sure if it's a real concern, but I've never seen this before. Didn't think I was doing any more braking than usual. Anyone have this problem? Should I worry?

[S51]

wow. i personally haven't experienced this on my bike but i've seen it on motorcycles at the race track.

in my past experience as a race mechanic, that usually means that you're really on the brakes and/or overheating them. usually when that happens we deglaze the rotors or replace them.

[theclayster]

i think it means that you overheated your brakes...you must have been on them too much when going downhill...don't brake as much, in smaller intervals and not all the time

[G-Ride]

Rotors get pretty hot during extended braking so that's fairly normal over time. You're probably getting close to needing new ones, judging from the grooves and the glaze, but I'd say you're good for awhile.

[onegymrat]

I think I need to wean myself from overbraking, since this is a clear sign. I just didn't think this could be normal. Just wouldn't want some weird brake failure when I need it most. Will keep an eye on this after Saturday (next ride) and see how much more it glows. If it gets worse, I figure I would have to get a new rotor. Then again, if I just eased off the rear brake...

[bighit8]

Looks like you are due for new pads from the looks of it.Check for any contamination as well.Assuming you weren't on the brakes to hard, you have some other issue.Caliper hangin up???

[faded1004]

my call would be...

colors - would say from high heat... could be from a long downhill run...
uneven darkness on edges - check pads... might be uneven?

[L8 APEKS]

It's called "blueing". You basically burnt the rotors. Your pads may be glazed over too; take them out and see if they appear shiny. If they do, rub the friction material with sandpaper or something similar to expose a fresh layer.

I'd replace the rotors ASAP and avoid serious downhills until you get them replaced. They are *probably* OK, but for $15 I wouldn't take the risk.

[Winger]

If you're buying a new rotor, you might consider replacing with a larger rear rotor. It will help dissipate heat and hopefully avoid this in the future.

The added cost for a larger rotor is like $15 for the spacer....assuming your bike can accept the larger size.

[Lefty Kev]

Since something like 70-80% of your stopping power is in the front brake, I'm surprised the bluing isn't present on the front rotor as well as the rear

Are the rotors warped from the heat? If so, you might want to consider replacing them as others have suggested since warped rotors could potentially damage other componentry.

And remember: Accessive braking results in less control. As Brian Lopes states in his book Mastering Mountain bike Skills: "...Riding problems seldom arise from not braking often enough. They usually come from braking too often. In sketchy situations, you're just a twitch away from an over-the-bars calamity..."

[onegymrat]

Originally Posted by L8 APEKS

It's called "blueing". You basically burnt the rotors. Your pads may be glazed over too; take them out and see if they appear shiny. If they do, rub the friction material with sandpaper or something similar to expose a fresh layer.

I'd replace the rotors ASAP and avoid serious downhills until you get them replaced. They are *probably* OK, but for $15 I wouldn't take the risk.

Just put on a new rotor, had one laying around. I just don't like the look of those burn marks. Got some new pads on there also. The old ones are not totally worn yet, but are definitely shiny. Will sand it down as you suggested, and help even the surface, should have some life in them still. Can't put on bigger rotors, it's an '07 Specialized Epic, no room for that. As I mentioned, will just have to learn to ride! Thanks everyone for helping.

So I guess that rotor is wasted?!

[Rockinthecasbah]

looks fine if it isnt warped, all rotors get heat marks on them if you ride your bike anywhere you need to use the brakes!. As long as the grooves on those things aren't bad your cool, just my opinion but riding where we ride if you replaced rotors everytime the blue'd we woudl go broke

[faded1004]

yea, just make sure the rotor is straight and the pads are semi flat and not glossed... i think you will be fine, unless you feel something really weird in the brake feel...

[guero]

Originally Posted by Rockinthecasbah

looks fine if it isnt warped, all rotors get heat marks on them if you ride your bike anywhere you need to use the brakes!. As long as the grooves on those things aren't bad your cool, just my opinion but riding where we ride if you replaced rotors everytime the blue'd we woudl go broke

i agree. depending on where you ride, and how hard you ride, you will be on the brakes alot. my rear rotor has the bluing as well...im not sweating it though.

[onegymrat]

No, rotor is not warped at all nor were there any unusual feeling about the performance. I just found the bluing when I was about to clean it up. The pads, however, look really weird. You can see what it did to the contact surface of the rotor.

[L8 APEKS]

Originally Posted by Lefty Kev

Since something like 70-80% of your stopping power is in the front brake, I'm surprised the bluing isn't present on the front rotor as well as the rear

You know, this is what I thought too, at first...but if you're on a downhill, you are probably using the rear much more often than the front to scrub off speed, change your line, etc.

While weight is transferred forward and your front is certainly doing the bulk of the work if you squeeze both levers to STOP, I think the rear is under more stress on a downhill section because it's activated more often than the front, building up heat the whole time.

Also, on the 203mm suggestion...I have to say, I am not sure 203's were the best choice for me. I got them because I'm heavy and I had just moved from V-brakes which didn't work as well as I wanted for stopping.

But the 203mm on my Avid BB7 is almost *too* much, because there's not much modulation when you're bouncing down a trail at 30mph, and most of the time it's either "no brakes" or "fully locked up and skidding." It's hard to just slow down without locking the rear with the 203mm, and I'm wondering if a smaller rear rotor might help even that out.

[2wheel_lee]

I've had quite a few rotors discolor like that. The only problem is when you touch the rotor to the inside of your leg right after doing that. BTDT. The Hayes scar has gone away (although I thought it was kind of cool).

Other than the grooves, that rotor is fine. Rotors are capable of tolerating a great deal of heat. They're stainless steel!!!

The pads may be glazed and may need to be sanded (as posted above).

The debate between 160 vs. 180/185 vs 203 rotors will always exist - even within a given ride. I set my bikes up to have the smallest rotor I can get away with for the riding style of the bike or the ride. In other words, although I could install 203 mm rotors on all of my bikes, I don't care to carry around the weight all the time. Sometimes, though, I push the bike outside of the normal operation boundry and overheat the brakes and discolor a rotor or two (yes, you can cook the front like this as well).

If you regularly overheat the braking system - you should know when this happens because they will fade - try installing the next size larger rotor.

[wgb]

I suggest checking your pads. I just replaced my Hayes Sol with the 9s, and I noticed the same markings on my rotors. When I pulled the padds out, one of them was chipped. I am still using the same rotors, only because I took them to the LBS (Jensons) and they told me that there was no major damage. I have replacement rotors but I don't want to use'em if I don't have to.