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  1. #1
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    Brake rub on pedal stroke only?!

    My setup is a 2008 Trek Fuel EX 8, XT brakes, Mavic 819 wheels, XT hubs, 160mm shimano rear rotor. I am not a small rider at 6' 235 lbs.

    I upgraded brakes from avid juicy's to XTs and I haven't been able to get my rear brake adjusted right. I have gone to the LBS to have them adjusted with rotor true'd without success. Bike leaves bike shop with no rubbing and no sounds coming from rear brake. I get on my bike and pedal hard, my rear brake starts rubbing. If I coast, there is no rubbing. Is the frame flexing? my wheel flexing? Are the clearances on the shimano brakes really that tight?

    Any help is appreciated.

  2. #2
    Commit or eat sh!t
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    Most likely your frame is flexing as you pedal, especially given your weight.

  3. #3
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    I dunno, I never had this problem with the avid juicy's....I read that it could be play in the hub or the skewer isn't tightened enough. Might take it to LBS to get hub looked at.

  4. #4
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    Could also be that the brakes were overfilled during the bleed reducing clearance between pad and rotor.

    Rotate the brake lever so that it is horizontal, pop the cap and diaphragm on the master cylinder reservoir, reset the pistons so that they are flush with the body of the caliper, replace the diaphragm and cap, then wipe up the drips with isopropyl.

  5. #5
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    Thanks for the response. Is there any way of knowing it is overfilled without opening it up? Anything I can see from the caliper operation that would indicate this?

  6. #6
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    You've mentioned that you heard that it could be that the rear skewer may need to be tightened which is what I suggested. So, did you crank it down?

  7. #7
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    Quote Originally Posted by Cable0guy View Post
    Most likely your frame is flexing as you pedal, especially given your weight.
    This and potential flex on your wheels too.
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  8. #8
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    Yes, I cranked down this morning and tried riding again before going to work...still rubbing when I ride it. Worse when I pedal.

  9. #9
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    Quote Originally Posted by drm31078 View Post
    Yes, I cranked down this morning and tried riding again before going to work...still rubbing when I ride it. Worse when I pedal.
    I'm just guessing, but could it be you have gained some weight since you changed the brakes? That could account for some flex in the wheel/ frame, right? I had a bike that used to creak a lot, but when I lost weight, the problem lessened.
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  10. #10
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    Zarr, what are you implying!? Haha...although I could probably lose a few (or many) pounds, I gotta think a bike should be designed to accommodate me. I called the shop and I am going to bring it in tomorrow...

    Reading more and more, the XT hubs seem to have some reliability problems with the cones loosening. Perhaps there is some play in the hub under load. With what seems to be a tight tolerance between the caliper/rotor, it probably doesn't take much play to get them to rub. I will let you all know.

  11. #11
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    OK, then perhaps worn rear suspension bushings/bearings/pivots?

    Loose spokes on the rims?

    Worn rear hub bearings?

    Loose rotor?

    Loose cailper mounting?

    Have you taken your bike on a normal long ride to see if the new brake sysem wears in?

  12. #12
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    Quote Originally Posted by drm31078 View Post
    Zarr, what are you implying!? Haha...although I could probably lose a few (or many) pounds, I gotta think a bike should be designed to accommodate me. I called the shop and I am going to bring it in tomorrow...

    Reading more and more, the XT hubs seem to have some reliability problems with the cones loosening. Perhaps there is some play in the hub under load. With what seems to be a tight tolerance between the caliper/rotor, it probably doesn't take much play to get them to rub. I will let you all know.
    Nah partner, I'm not trying to imply anything. I weigh more than you do (260),so far be it from me to imply you are too heavy. But when you are dealing with close tolerances like we do with our bikes, weight can definately be a CONTRIBUTING factor in misalignment issues, could it not? So far all the replies you have got sound good to me. Let's cover all the bases to get you on your way. I am currently building more than one bikes myself right now, so I want to thank you for your thread. You are on the right website to learn, I know that much. Hang in there. Continue to post up & help out when you can. And pay no mind to hecklers and trolls. thanks again.---zarr
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  13. #13
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    Sometimes for me if the rotors get grungy they will start doing what you describe. Most often when I clean the rotors it will stop doing it. Good luck!
    I'm not a vegetarian because I love animals, I just hate vegetables.

  14. #14
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    Might not help, but I bled my brakes in the cold and when the temps went up they would get a little tight and rubbed easy. Got the rubbing when mashing hard, rebled them while hot and problem went away.

  15. #15
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    Quote Originally Posted by drm31078 View Post
    Thanks for the response. Is there any way of knowing it is overfilled without opening it up? Anything I can see from the caliper operation that would indicate this?
    Symptoms would be:

    -Reduced clearance between pad and rotor (duh, I know)

    -Weeping oil from somewhere in the brake system: around the pistons, around the MC reservoir, or the lever plunger (all of these are very unhappy things requiring replacement of parts)

    -Difficulty in resetting pistons "all the way." If it is, DON'T try and force them back in with the reservoir cap on as it strains the seals. Shimano makes their seals out of tissue paper, in my experience.

    -"Tight" brake levers. Rear brakes will often feel less tight than the front, because the fluid travels through more line (which may expand under pressure). That is the normal condition. If it is the case that your rear lever feels tighter than the front, it is a sign of overfill.

  16. #16
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    You might get some answers by posting up some threads in the Clydesdale/Tall Riders forum which is dedicated to heavier and tall riders. someone there might even have the same bike/ problem you have. You will get less responses there though, because the forum is mainly meant for those riders.but it is very helpful for heavy/tall riders.
    ---Z
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  17. #17
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    Well, I took it to my LBS, which is a Trek store. They spent a better part of the day doing the following:

    Check caliper alignment
    True slight wobble in rotor
    Serviced hub (tightened slightly)
    Checked spoke tension
    Checked brake fluid
    Checked rear triangle for cracks
    Checked sprocket tightness

    Result = they said that it doesn't sound as bad, but the rub is still there on a hard pedal.

    Basically, they could not figure it out and are attributing it to frame flex. Keep in mind these are not big guys riding the bike. They also said if this was a new bike, that amount of frame flex would not be acceptable. However, since it's an older bike, Trek will not warranty the frame for some noise from the brakes.

    WTF. Try another bike shop?

  18. #18
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    Quote Originally Posted by drm31078 View Post
    Well, I took it to my LBS, which is a Trek store. They spent a better part of the day doing the following:

    Check caliper alignment
    True slight wobble in rotor
    Serviced hub (tightened slightly)
    Checked spoke tension
    Checked brake fluid
    Checked rear triangle for cracks
    Checked sprocket tightness

    Result = they said that it doesn't sound as bad, but the rub is still there on a hard pedal.

    Basically, they could not figure it out and are attributing it to frame flex. Keep in mind these are not big guys riding the bike. They also said if this was a new bike, that amount of frame flex would not be acceptable. However, since it's an older bike, Trek will not warranty the frame for some noise from the brakes.

    WTF. Try another bike shop?
    Either that or take one less bite off that hamburger.
    hahahaha
    Hey, i'm sorry man. I just couldn't resist the moment.
    I'm sorry.
    Nah, but seriously, if you did all that, maybe you can get a brakeset that permits more pad adjustment. I am beginning a couple of builds using avd BB7 mechanicals, which have ability to adjust both the inner & outer pads independently. Not sure how they work yet though.Come to think of it, maybe there's ways to shim or file down some part of the mounting process to allow enough space between the pads to keep them from rubbing.Take a good look at the way everything lines up. Twweking might help.
    Either that or Slim-Slow.
    Ask around in the Clydesdale furum. Might help.
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  19. #19
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    Find out which way the calipar moves when pushing hard and adjust the gap accordingly.
    lean forward

  20. #20
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    Quote Originally Posted by drm31078 View Post
    Well, I took it to my LBS, which is a Trek store. They spent a better part of the day doing the following:

    Check caliper alignment
    True slight wobble in rotor
    Serviced hub (tightened slightly)
    Checked spoke tension
    Checked brake fluid
    Checked rear triangle for cracks
    Checked sprocket tightness

    Result = they said that it doesn't sound as bad, but the rub is still there on a hard pedal.

    Basically, they could not figure it out and are attributing it to frame flex. Keep in mind these are not big guys riding the bike. They also said if this was a new bike, that amount of frame flex would not be acceptable. However, since it's an older bike, Trek will not warranty the frame for some noise from the brakes.

    WTF. Try another bike shop?
    I hate bike shops almost as bad as I hate car shops.all they are is pocket Drano. But if it wasn't for them, I never would have got so interested in building bikes.it's because of their shyster rip-off actions a lot of folks learn about bikes I guess. one thing I know...if you keep trying you WILL solve your problem and any other bike problem.. without them. Just keep posting up... the guys on this site won't let you down.
    Hang in there.
    roccowt.
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  21. #21
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    As I mentioned earlier, go for a long, hard ride and work the Hell out of the brakes. They may self adjust or wear in.

    If not, then it looks like it's time for a brand new, late model frame.

  22. #22
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    Quote Originally Posted by ambassadorhawg View Post
    As I mentioned earlier, go for a long, hard ride and work the Hell out of the brakes. They may self adjust or wear in.
    That may definitely be the problem and I would not be surprised if it solved your issue.
    2012 Intense M9
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  23. #23
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    Let me show you how wack the Local Bike Shop is...and how a good nap helps me (a old dude ).Well, not that old. to think.
    Why didn't the LBS have the sense enough to put a different wheel/tire on your bike so you could test ride and find out if your frame is flexing? Boy, they're a big help, aren't they? that's why I try to learn as much as I can from other sources. I get sick just looking at the bike shops where I live.Every single one of them has tried to rip me off...exept one and he went out of business. he was a nice guy too.(Sad).Try to get e hold of a different wheel at least long enough to try to find out what the problem might be.
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  24. #24
    ouch....
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    What kind of quick release do you have??

    Good ol shimano xt hold things very well.
    Riding.....

  25. #25
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    I really think you should try letting some fluid out of the system. Make sure the pistons are flush with the caliper body before you put the res cap back on. Microliters of fluid can be pretty significant in pad clearance issues.

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