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  1. #1
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    Rotor Discoloration

    Is this normal? It is not dirt. And I dont think it is rust, because it wasnt there before I rode. Avid BB5 160mm.




  2. #2
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    That's discoloration from excessive heat... You're ridin them brakes too much boy!!
    No but really, you could be overusing them.
    Height/weight?
    Do you use your front brake to help slow down as well?
    Try pulsing your brake on/off during long descents so everything can have a second or two to cool down.
    I wouldn't worry about the slight color change on the rotor, but overheating can:
    glaze your pads = $$ have to resurface them or get new pads
    slightly boil your fluid = $$$ have to bleed them, possibly a complete oil change
    REALLY boil your fluid = $$$$$ screw up all kinds of internal stuff that will degrade from the heat i.e. seals, bushings, etc.

  3. #3
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    Quote Originally Posted by CheeseSoda
    That's discoloration from excessive heat... You're ridin them brakes too much boy!!
    No but really, you could be overusing them.
    Height/weight?
    Do you use your front brake to help slow down as well?
    Try pulsing your brake on/off during long descents so everything can have a second or two to cool down.
    I wouldn't worry about the slight color change on the rotor, but overheating can:
    glaze your pads = $$ have to resurface them or get new pads
    slightly boil your fluid = $$$ have to bleed them, possibly a complete oil change
    REALLY boil your fluid = $$$$$ screw up all kinds of internal stuff that will degrade from the heat i.e. seals, bushings, etc.
    thanks for the quick reply.
    Last edited by aybdude42; 01-03-2009 at 06:39 PM.

  4. #4
    sweet!
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    Looks like your brake rotor got HOT, don't worry however, mine look exactly the same.
    I'm running Avid Juicy 5 with Alligator Windcutter 203mm front, 180mm rear. Even though I use my front brake far more then my rear brake, my rear brake rotor is more discolored then my front one, that tells me that the 23mm difference in rotor size makes a big difference in their ability to dissipate heat. Maybe you should go to a larger rotor, if the discoloration makes you nervous. I'll just keep my rotors and think of the discoloration as a badge of honor.
    cheers
    "It's a Sledgehamer" "Dang! You got shocks, pegs...lucky! " Napoleon Dynamite & Pedro Sanchez

  5. #5
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    That's a huge debate, actually. A search on these forums will turn back PAGES of mindless arguing about rotor size vs force vs friction leverage e=mc^2 blah blah... But as far as my $0.02 go, I would say that for somebody your size, 7" discs would probably do better than the 6" you've got there (I assume you have 6" front and rear). If your fork can take it, perhaps even an 8" front. Me + gear + sled = about 225# and I've never had heat issues with 6" rotors. That discoloration you have in the picture is actually pretty mild compared to what some people get. That considered, if that hill was about as gnarly as you go down, 7" should probably be enough.

  6. #6
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    Quote Originally Posted by CheeseSoda
    That's a huge debate, actually. A search on these forums will turn back PAGES of mindless arguing about rotor size vs force vs friction leverage e=mc^2 blah blah... But as far as my $0.02 go, I would say that for somebody your size, 7" discs would probably do better than the 6" you've got there (I assume you have 6" front and rear). If your fork can take it, perhaps even an 8" front. Me + gear + sled = about 225# and I've never had heat issues with 6" rotors. That discoloration you have in the picture is actually pretty mild compared to what some people get. That considered, if that hill was about as gnarly as you go down, 7" should probably be enough.
    Well I have the Dart 3 fork and it says max rotor size 160mm, what can go wrong if i put 203mm rotors on there?

  7. #7
    sweet!
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    Last year Rock Shox had a misprint in the specs. for the Dart 3, it said max rotor size 203mm, so I went out and bought a 203mm front rotor. This was a big mistake, the poor fork would flex so bad under hard braking, if I didn't have a good grip on the bars the entire bike would pull left off the trail and into a tree! (I didn't notice the pull with 160mm rotors)
    I had to upgrade my forks, because I wasn't going to downgrade my brakes. I now have a Rock Shox Recon that is 3x stiffer then my Dart 3, and what a difference they made.
    "It's a Sledgehamer" "Dang! You got shocks, pegs...lucky! " Napoleon Dynamite & Pedro Sanchez

  8. #8
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    it rips the mounts off of your fork.

  9. #9
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    If you put too large of a rotor on, it COULD break the mounts/lowers etc, but it's much much much more likely that the front tire would lock before that happens. The only way it would break the mounts, as best I can imagine (I've taken a few physics classes hehe) is if you JAMMED the breaks on HARD and the force all made it into the mounts before the tire managed to break free... But I've never seen it happen.

    Diamondhead's story is much more the case. Your fork will try to flex into the braking forces, and you'll have to really fight it to keep going straight. I don't know the actual specs on your fork, but pushing 300#, you might consider a beefier fork anyways, and that would probably mean one that allows for larger rotors anyways. 2 birds one stone type of a deal.

  10. #10
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    Quote Originally Posted by CheeseSoda
    If you put too large of a rotor on, it COULD break the mounts/lowers etc, but it's much much much more likely that the front tire would lock before that happens. The only way it would break the mounts, as best I can imagine (I've taken a few physics classes hehe) is if you JAMMED the breaks on HARD and the force all made it into the mounts before the tire managed to break free... But I've never seen it happen.

    Diamondhead's story is much more the case. Your fork will try to flex into the braking forces, and you'll have to really fight it to keep going straight. I don't know the actual specs on your fork, but pushing 300#, you might consider a beefier fork anyways, and that would probably mean one that allows for larger rotors anyways. 2 birds one stone type of a deal.
    yeah, that sounds right.

    seems like all the good 29er forks other than the reba are above $400... (but i believe that is a discussion for the 29er forum)

  11. #11
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    http://www.jensonusa.com/store/produ...solute+08.aspx
    I would say at your size, 8" front and 7" rear. I run that combo and am about your size.
    That link to that 29er fork is a pretty damn good deal. There are others to be had if you search hard enough.
    You'd prolly be much happier with a different fork as well as larger rotors.
    BTW, did you upgrade the springs in your dart to XtraStiff?
    Look, whatever happens, don't fight the mountain.

  12. #12
    sweet!
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    Quote Originally Posted by savagemann
    http://www.jensonusa.com/store/produ...solute+08.aspx
    I would say at your size, 8" front and 7" rear. I run that combo and am about your size.
    That link to that 29er fork is a pretty damn good deal. There are others to be had if you search hard enough.
    You'd prolly be much happier with a different fork as well as larger rotors.
    BTW, did you upgrade the springs in your dart to XtraStiff?
    L@@KS like a sweet deal on some sweet forks, however those forks are only available in 20mm hex axle, so this can get real expensive real fast.
    shopping list:
    1. two new eight inch rotors (since you are rolling on a 29r go 8" front and rear)
    2. one sweet Manitou Minute 29 Absolute fork w/ 20mm hex axle
    3. one front wheel assy., or relace a new hub that will accept the 20mm axle
    4. caliper mounts and addapters to fit the larger rotors

    Don't get me wrong these changes will transform your ride from a "flexible flyer" to the "Rock of Gibraltar", especially someone of your size riding a 29" bike.
    Good Luck and Cheers
    "It's a Sledgehamer" "Dang! You got shocks, pegs...lucky! " Napoleon Dynamite & Pedro Sanchez

  13. #13
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    Quote Originally Posted by Diamondhead
    L@@KS like a sweet deal on some sweet forks, however those forks are only available in 20mm hex axle, so this can get real expensive real fast.
    shopping list:
    1. two new eight inch rotors (since you are rolling on a 29r go 8" front and rear)
    2. one sweet Manitou Minute 29 Absolute fork w/ 20mm hex axle
    3. one front wheel assy., or relace a new hub that will accept the 20mm axle
    4. caliper mounts and addapters to fit the larger rotors

    Don't get me wrong these changes will transform your ride from a "flexible flyer" to the "Rock of Gibraltar", especially someone of your size riding a 29" bike.
    Good Luck and Cheers
    thanks for the advice guys...looks like its time to start saving

    also, the spring is "firm" and seems to be ok, but my preload is stuck at max :\

    btw, what do you think the total cost of this upgrade would be?

  14. #14
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    http://www.jensonusa.com/store/produ...+Wheelset.aspx
    Pretty good deal on a 29er wheelset above. I'm sure there are better deals to be had. But lets figure $200 minimum for a closeout wheelset. Prolly could find just a front wheel for around $100 for a good one on closeout.
    Adapters for the rotors will run you between 20-30 for both. Depending on which rotors you want to get, they can be found between 15-30 each. Like this alligator here..........
    http://www.pricepoint.com/detail/162...rake-Rotor.htm

    So lets say
    $270 fork
    $25 adapters
    $40 rotors
    $100 wheel (minimum)
    about $450 after shipping.
    Look, whatever happens, don't fight the mountain.

  15. #15
    I Tried Them ALL... Moderator
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    Quote Originally Posted by aybdude42
    thanks for the quick reply.

    i'm 6'6" 300+.
    i was using the front and rear brake about equally, and "pulsing" occaisonally, but it was a huge steep hill.
    they are mechanical brakes too.
    do you think that bigger rotors would be good if i upgrade or these break?
    Jumbo Clydes like you need a minimum 185mm rotor/front, to improve stopping efficiency. I would go 185mm x 2 for the best results. Feathering your brakes, prevents heat glazing. It's amazing how a few milliseconds of cool time can make your rotors appear!
    "The mind will quit....well before the body does"

  16. #16
    sweet!
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    I've done some searching around also and this is what I have been able to find.
    we already know the fork will cost $270

    Rotors 203mm front and rear $32.00 http://www.pricepoint.com/detail/157...Wavy-Rotor.htm

    Wheelset 29" all mountain 20mm thru axle $230.00 http://www.bicyclewheelwarehouse.com...d&productId=85

    Caliper mounts $18.00 http://www.pricepoint.com/detail/167...-Included).htm http://www.pricepoint.com/detail/167...-Included).htm

    BTW if you plan on keeping your Avid bb5 mech. brakes that's fine, however do not buy the Alligator serration rotors (as recommended by savageman), I recommend buying the wavy rotors, the bb5 pads are too small for the large serrations in the those rotors, they will vibrate like crazy, trust me I know first hand. I now run my serrated rotors with Avid Juicy 5.

    Start save'n and Cheers
    "It's a Sledgehamer" "Dang! You got shocks, pegs...lucky! " Napoleon Dynamite & Pedro Sanchez

  17. #17
    I think we should go back
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    you guys lock up your front brakes? Wow I flip over the handle bars or get my back tire in the air before they lock up. Even when i lean back. I guess if I am on sand I can lock up the front tire and skid. I weigh 90 pounds and do you think decending about 3000 feet in 2 minutes would discolor the rotor if I was consistently using the rear or front brake the whole time? Also which one gets hotter, the front or rear?

  18. #18
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    Quote Originally Posted by drain bamage
    ...decending about 3000 feet in 2 minutes would discolor the rotor if I was consistently using the rear or front brake the whole time...
    3000' in 2mins. wont discolor your rotors because you wouldn't be using your brakes
    Honestly... ahh I give up

  19. #19
    I think we should go back
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    Or sorry I mean in 20-30 mins LOL didnt put the zero. And it is going down the Utah snowbird mountain. I am going to take the tram up and ride down

  20. #20
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    at 90#, you could have 160mm rotors and burn them all the way down the sheer side of half dome and not have any issues haha

  21. #21
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    I musta been really tired this morning when I linked to that wheelset, I don't even think it's 20mm ta.
    The set diamondhead posted looks to be a good deal.
    Look, whatever happens, don't fight the mountain.

  22. #22
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    Is this the same?
    It seems the opposite: darker on the pad contact area.

    It is a Tektro rotor (used with a Tektro Auriga Comp hydraulic system).

    What I noticed is that during big descents, the sound of the brake changes, it gets much louder (but not squeaking). And may be the lever feels stiffer. But I haven't noticed less braking power, just different (and louder) sound.

    Does it mean anything, or is it all normal?
    Attached Images Attached Images

  23. #23
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    Quote Originally Posted by aybdude42
    thanks for the quick reply.

    i'm 6'6" 300+.
    i was using the front and rear brake about equally, and "pulsing" occaisonally, but it was a huge steep hill.
    they are mechanical brakes too.
    do you think that bigger rotors would be good if i upgrade or these break?
    One thing, I notice that Avid rotors tend to get hot fast. I put one one my magura martas on the the rear and it got hot faster than the Magura SL drilled rotor I had on there. It was way louder too. The Magura SL drilled rotors are going for $20 at pricepoint.
    Lead by my Lefty............... right down the trail, no brakes.

  24. #24
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    Quote Originally Posted by leoh
    Is this the same?
    It seems the opposite: darker on the pad contact area.

    It is a Tektro rotor (used with a Tektro Auriga Comp hydraulic system).

    What I noticed is that during big descents, the sound of the brake changes, it gets much louder (but not squeaking). And may be the lever feels stiffer. But I haven't noticed less braking power, just different (and louder) sound.

    Does it mean anything, or is it all normal?
    It's normal for organic pads. If you are running cindered (sp?) pad, that maybe burned on oil from pad contamination. But from the pic, yours dont even look that dark, your fine.
    Lead by my Lefty............... right down the trail, no brakes.

  25. #25
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    Im riding a 29er with 203mm BB7s on it with a Reba SL and really notice the upgrade over the Dart 3 that came with the bike. Im only about 140 fully decked out to ride so i would def upgrade fork and rotor size with your dimensions.

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