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  1. #1
    GoCyco
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    complete rotor destruction!

    I searched and didn't find any results on rotor cracks or rotor failures. This happened to me 2 days ago and it is an absolute mystery what exactly could have caused this amount of damage.

    I just started to descend, did not hit anything, did not crash, and all of a sudden there's this incredibly loud noise and I think my rear wheel locked up at this point. When I stopped I thought maybe I picked up a stick that was lodged in the wheel or something like that. But then I see the rotor all mangled. Very weird. No idea about what could have happened. Did the rotor crack and part of it hit the caliber as it spun around and then with the force of the bike descending and the wheel spinning it just went into complete pretzel mode?
    Attached Thumbnails Attached Thumbnails complete rotor destruction!-img_1292.jpg  


  2. #2
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    Did it hurt the wheels? Are those formula discs?

  3. #3
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    FUBAR for sure!

    I would take it apart, photo every mm of it looking for signs of previous cracking, then send it to the factory for them to look at. And check your front brake too!!
    What brand rotor?
    Last edited by LWright; 11-19-2012 at 01:40 AM. Reason: not much surface on that rotor

  4. #4
    GoCyco
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    Wheel seems OK

    Quote Originally Posted by mazspeed View Post
    Did it hurt the wheels? Are those formula discs?
    Formula brakes and rotor. Front rotor was replaced with a larger Avid one as the stopping power was good enough with the stock rotor.

  5. #5
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    Just as well that wasn't the front disc, or that could have caused some pain for you! I don't think I've ever even heard of anyone breaking an actual rotor before.
    Maybe a rock of something did get caught up in the rotor, causing it to jam/break, and consequently end up looking like that. I'd make sure the the rear wheel is still good to go and hasn't sustained any damage either.
    I don't crash, I just have slightly uncontrolled dismounts!

  6. #6
    GoCyco
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    Front failure would have been a lot of pain! As it was, I still had a good 275m of steep descending and the front wheel was difficult to keep from locking up and skidding. I almost went of the bars a couple times.

    I think you may be right about the cause. I will take a picture of the brake pads later and add it here. I remember seeing a deep scratch on one of them. Something must have went inbetween and jammed the rotor. Funny, looking at the rotor again, the outer ring is not broken, just folded on itself.

  7. #7
    Trail Tire TV on blogger
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    just a guess... but from the look of the one bolt missing and the torn threads only on the very outer most "enter/start" section, and it looks like the inner threads are fine...? I'm guessing you had at least one loose or damaged bolt...

    if the bolt WAS completely torn from the hub... the hub is toast.. DO NOT try and use it by re-threading and using a diff bolt... Aluminum massively weakens under high stress and this could easily happen again if the material has been stretched/stressed...
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  8. #8
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    You can see by the look of the rotor you have got something caught in it for sure.
    Theres no other explination i can think of to create that sort of carnage, ive never seen anything like it.
    Id say a stick started it then your bike might have done the rest of the damage getting a bit of the rotor caught on it
    Tine for a new hub n rotor
    Dont ever let the truth get in the way of a funny story....

  9. #9
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    just to add to that theres no way its from a rock getting stuck between the rotor and pads, theres only 1mm at most on each side of the pads, its just impossible for that to cause the destruction there, and if something did get caught in there theres no way that it would have the strength at 1mm or less to do that damage, just not possible.
    youve got something caught in the rotor, to shred your rotor and dethread a bolt like that it would take some massive force to do that
    Dont ever let the truth get in the way of a funny story....

  10. #10
    Trail Tire TV on blogger
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    Quote Originally Posted by Tone's View Post
    just to add to that theres no way its from a rock getting stuck between the rotor and pads, theres only 1mm at most on each side of the pads, its just impossible for that to cause the destruction there, and if something did get caught in there theres no way that it would have the strength at 1mm or less to do that damage, just not possible.
    youve got something caught in the rotor, to shred your rotor and dethread a bolt like that it would take some massive force to do that
    actually there is.. the vent holes on those are large enough that something "could" get caught in there and hit the outer part of the caliper... but there would be noticeable damage to the entrance of the caliper,... and I agree it's very, very unlikely...

    also the bolt/hub interface is about the strongest part of the whole thing, to actually tear the bolt out of the hub is not likely with the failure being out by the caliper.. the arms of the rotor would snap first (like all the rest did) most likely something happened to/with that bolt...
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  11. #11
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    Looks to me like someone was only using 3 mounting bolts, is it true? You can also see the fancy red spokes are scratched, therefore the wheel IS damaged. Spokes are part of a wheel, correct?

  12. #12
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    Quote Originally Posted by thomllama View Post
    actually there is.. the vent holes on those are large enough that something "could" get caught in there and hit the outer part of the caliper... but there would be noticeable damage to the entrance of the caliper,... and I agree it's very, very unlikely...

    also the bolt/hub interface is about the strongest part of the whole thing, to actually tear the bolt out of the hub is not likely with the failure being out by the caliper.. the arms of the rotor would snap first (like all the rest did) most likely something happened to/with that bolt...
    LOL, C'mon thomllama, what are the chances of that, youd have better chance of winning the lotto than that happening
    Dont ever let the truth get in the way of a funny story....

  13. #13
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    Have the rotors seen extreme thermal stress at any point? Like getting hot down a run and then quenched in a puddle?
    I can barely get my mouth around it.

  14. #14
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    Pedalphile,......really........are you takin the piss? lol
    I know what your gettin at, but there is no chance that the above pic has any link to thermal stress,
    Dont ever let the truth get in the way of a funny story....

  15. #15
    Trail Tire TV on blogger
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    Quote Originally Posted by Tone's View Post
    LOL, C'mon thomllama, what are the chances of that, youd have better chance of winning the lotto than that happening
    ya,... but it's Possible... LOLOL
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  16. #16
    Give it a crank
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    Take a very close look at each of the arms connecting the bolts to the disc contact area. If one of the arms deviated far enough to catch on the caliper, there should be an obvious dent on both the arm and the caliper where they made the initial contact. If that's what happened, then it's on to see what caused it, that missing bolt looks too suspicious.

  17. #17
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    Quote Originally Posted by Tone's View Post
    just to add to that theres no way its from a rock getting stuck between the rotor and pads,
    That is BS
    theres only 1mm at most on each side of the pads, its just impossible for that to cause the destruction there, and if something did get caught in there theres no way that it would have the strength at 1mm or less to do that damage, just not possible.
    youve got something caught in the rotor, to shred your rotor and dethread a bolt like that it would take some massive force to do that
    I had a rock jump up and get stuck in my front rotor fortunately it only dinged up one arm ...

    The rotor did not collapse..

    But then it is a good old shimano rotor.

  18. #18
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    Quote Originally Posted by Tone's View Post
    Pedalphile,......really........are you takin the piss? lol
    I know what your gettin at, but there is no chance that the above pic has any link to thermal stress,
    If the metal had a defect, extreme thermal stress could allow the defect to become a crack. If that crack then turned into a broken arm, chaos might ensue.

    Meterial defects in stainless parts combined with corrosion and stress have brought down airliners, and one could assume there is quite a bit more quality control in aircraft parts than mtb parts (I believe it was a 747 that dropped an engine which ripped out the second engine on that wing, causing a disaster...I can probably look this up if needed - it's covered in a Modern Marvels/Engineering Disasters episode).

    I don't think anything short of expensive failure analysis via a metalurgy lab could pinpoint what went wrong here, so speculation is all we've got unless there is other evidence available.

    -Pete
    I can barely get my mouth around it.

  19. #19
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    ^^ fair enough Pete, good point, i was gonna say that thermal stress could only result in cracking the rotor, i suppose it might have cracked n made it easier for the break, but you can see the massive bending of the rotor, im not sure its cause of that, but you have a valid point mate, cheers
    Dont ever let the truth get in the way of a funny story....

  20. #20
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    Aloha Aizu1,

    I keep looking at the picture and that one rotor mounting hole looks clean. The bolt did not get pulled out so it must have been loose and eventually fell out. I'm guess with this but thinking the rotor eventually twisted enough till it bent around and broke. I've never seen anything like this so you'll probably be OK just replacing the rotor and new bolts. Definitely use lock-tite on the bolts. I was lucky a while back in that I used Ti bolts but didn't use lock-tite. The bolts were all getting loose, I heard some weird rattling. Caught it in time to get the bolts re-done with the lock-tite. Haven't had any issues with loose rotor bolts since then.

  21. #21
    007
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    I'd love to see a pic of this thing when its been removed from the bike/hub . . . .

    The first thing that came to mind is that the rotor was mounted backwards.
    Alcohol may lead nowhere, but it sure is the scenic route!

  22. #22
    GoCyco
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    Rotor was not mounted backwards.
    I have had issue with bolts loosening in the past. Usually I check them from time to time. However, I've been doing a lot skiing and hardly any biking lately. In this case I just topped off the air in the tires and took off.

    Regardíng the bolt hole, it's fine as this bolt was missing. So it was not "ripped" out of the hub as someone suggested.

    Appreciate all the theories!

  23. #23
    Spanish rider
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    Quote Originally Posted by aizu1 View Post
    Rotor was not mounted backwards.
    I have had issue with bolts loosening in the past. Usually I check them from time to time. However, I've been doing a lot skiing and hardly any biking lately. In this case I just topped off the air in the tires and took off.

    Regardíng the bolt hole, it's fine as this bolt was missing. So it was not "ripped" out of the hub as someone suggested.

    Appreciate all the theories!
    Make sure you use thread-locker next time, it's the only way to guarantee that they'll not unscrew by themselves.
    A pessimist is an experienced optimist

  24. #24
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    Quote Originally Posted by aizu1 View Post
    Rotor was not mounted backwards.
    I have had issue with bolts loosening in the past. Usually I check them from time to time. However, I've been doing a lot skiing and hardly any biking lately. In this case I just topped off the air in the tires and took off.

    Regardíng the bolt hole, it's fine as this bolt was missing. So it was not "ripped" out of the hub as someone suggested.

    Appreciate all the theories!
    Bolt missing as in 'it wasn't there on purpose' or 'wasn't there by accident'?

  25. #25
    GoCyco
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    Culprit?

    Could this be the issue? Looks like part of the spring went inbetween the pads. Enough to totally jam the system?
    Attached Thumbnails Attached Thumbnails complete rotor destruction!-pad.jpg  


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