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Thread: Damn Avid Mechs

  1. #1
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    Damn Avid Mechs

    No matter what I do, I just can't seem to get rid of my rear brake pads rubbing against the rotor while the wheel spins. Its a slight rub. Moreover, the rotor does not rub on the pads for the entire cycle, which seems to indicate that the rotor is bent. However, I have made endless adjustments, and relentlessly straigtened the rotor, but I just can't get rid of the rub unless I am willing to have the pads way open, which I do not like. Another damn thing is that I seem to be able to fix it while the bike is on the stand, but the rub returns as soon as riding begins. Ah.
    I AM JUST A JERK

  2. #2
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    Wow...

    Quote Originally Posted by Dirdir
    No matter what I do, I just can't seem to get rid of my rear brake pads rubbing against the rotor while the wheel spins. Its a slight rub. Moreover, the rotor does not rub on the pads for the entire cycle, which seems to indicate that the rotor is bent. However, I have made endless adjustments, and relentlessly straigtened the rotor, but I just can't get rid of the rub unless I am willing to have the pads way open, which I do not like. Another damn thing is that I seem to be able to fix it while the bike is on the stand, but the rub returns as soon as riding begins. Ah.
    I have the same problem with my rear Avid mech. My front has had no problems. The rear is a bit newer(2 months). I had my LBS straighten the rotor once but now the "sound" has returned. It sounds like a hinge that needs oil. When my bike is on the stand I also can make the "sound" go away but as soon as I am riding I hear it and it drives me crazy. It is also not a constant noise, it seems to come and go during my ride. I have been searching this site for an answer and have not come up with one yet. How new is your Avid rear? I am glad I am not the only one with this problem.
    Last edited by scheckler; 03-07-2005 at 03:25 PM. Reason: forgot

  3. #3
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    Quote Originally Posted by Dirdir
    Another damn thing is that I seem to be able to fix it while the bike is on the stand, but the rub returns as soon as riding begins. Ah.
    As in as soon as you apply the brakes for the first time, or within the first couple of pedal strokes?

    Is you're on a full-squish, check your cable routing. When you're on the bike, rear suspension sag might be putting unwanted tension on the cable, causing the caliper to actuate ever-so-slightly and yielding the mysterious rubbing.

  4. #4
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    You should be able to do minor adjustments to the rotor by hand, simply by eyeballing the rotor in the stand by looking through the caliper. You will see when the rotor contacts a pad. Remember the spot, back the rotor out until the spot is opposite the caliper and gently push or pull on the rotor by hand to true it up. You don't need a lot of force. Once it's running true in the stand, take it out for a LONG uphill ride and do a long fast descent working the brakes as much as possible to get the rotors good and hot. This should seat everything and usually stops the contact. If that doesn't work, you may have cable issues that are causing some activation.
    When I see an adult on a bicycle, I do not despair for the future of the human race. ~H.G. Wells

  5. #5
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    There's also the possibility of play in your rear hub causing rub that wouldn't happen in the stand...
    "...the people get the government they deserve..."
    suum quique

  6. #6
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    Quote Originally Posted by cutthroat
    You should be able to do minor adjustments to the rotor by hand, simply by eyeballing the rotor in the stand by looking through the caliper. You will see when the rotor contacts a pad. Remember the spot, back the rotor out until the spot is opposite the caliper and gently push or pull on the rotor by hand to true it up. You don't need a lot of force. Once it's running true in the stand, take it out for a LONG uphill ride and do a long fast descent working the brakes as much as possible to get the rotors good and hot. This should seat everything and usually stops the contact. If that doesn't work, you may have cable issues that are causing some activation.
    This is exactly what I do, but I use a small crescent wrench (trick I picked up from Larry at MtnHighCyclery) to do the truing. I find I can get a more exact position with the wrench, and I can apply the force gradually and check the rubbing again.

    For what its worth, my XT rotor has been true since I got it, but my Avid rotor has been problematic (needing lots of truing) the entire time. The good thing is that if the rubbing is bad, I can just dial the pads out a little bit and get rid of it till I get home and can put the bike in the stand.

  7. #7
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    maybe you need to face the disc tab mounts, but if you can get it to go away while on a stand, I'm assuming it is flex in the hub probably.

    I have always had rub on my avid mech, but I really don't care because it is on the front of my Trials bike, so I have the pads somewhat close, and I don't need high speed momentum efficiency on a bike that never see's any speed.
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    maybe frame flex...

    some frames give quite a bit under pedaling forces. You may be flexing the rear stays and causing the rotor to rub. My steel frame did that...now I'm about to have a brace welded in to try to "cure" that very problem. Typically the hub doesn't flex nearly as much as the rear stays.
    Mike

  9. #9
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    Quote Originally Posted by cutthroat
    You should be able to do minor adjustments to the rotor by hand, simply by eyeballing the rotor in the stand by looking through the caliper. You will see when the rotor contacts a pad. Remember the spot, back the rotor out until the spot is opposite the caliper and gently push or pull on the rotor by hand to true it up. You don't need a lot of force. Once it's running true in the stand, take it out for a LONG uphill ride and do a long fast descent working the brakes as much as possible to get the rotors good and hot. This should seat everything and usually stops the contact. If that doesn't work, you may have cable issues that are causing some activation.
    Yep to that - I actually take a sharpie marker and mark on the edge (not the FACE) of the rotor where the warp is - makes working with it much easier...

  10. #10
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    Maybe.....

    I don't have Avid brakes, but I have encountered the same problem you described with my Kona Kula Deluxe, it has Hayes hydro's. My Kula is a light bike & the frame is very flexible, if the rear caliper is centered on the rotor without my weight on the bike, I have found that when I get on the bike I can see the frame flex enough for the rotor to rub the inboard brake pad. So I have found that to stop the rubbing I must adjust the caliper towards the outer pad when there is no weight on the bike so it will be centered when I'm on it. Something to consider.....Good luck!

  11. #11
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    I thought about this

    Quote Originally Posted by Bikinfoolferlife
    There's also the possibility of play in your rear hub causing rub that wouldn't happen in the stand...
    but I got a brand new rear wheel, including new hub, this last Saturday and had the same problem. I am thinking it could be a skewer issue because I am running the same skewer but I really have no clue as to why this noise/rubbing is occurring.

  12. #12
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    Quote Originally Posted by scheckler
    but I got a brand new rear wheel, including new hub, this last Saturday and had the same problem. I am thinking it could be a skewer issue because I am running the same skewer but I really have no clue as to why this noise/rubbing is occurring.
    If the rotor is trued and running smoothly in the stand, and you have a reasonable spacing in the caliper, the issue is not with the brakes. it has to be frame flex, cable compression, loose axle, skewer or some other factor. I note that with my Hayes pads set fairly close to the rotor I can induce that "shing - shing" noise when I take a high G force turn at speed. The wheel itself is flexing under the load and causing the rotor to contact the pads. I run the Avids a bit more open and it doesn't happen with them, but if you hear the noise when you are JRA, you've got some flex related issue to track down. (spoke tension, hub tension, axle play, skewer tightness, inherent frame flex) You can try running the calipers more wide open and compensate for the lever feel by adjusting lever throw, reach and lever leverage - if you have the ability to tune the levers (Avid SD 7s, Ultimates, XTRs)
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  13. #13
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    This is an excellent point

    Quote Originally Posted by phobiaxc
    some frames give quite a bit under pedaling forces. You may be flexing the rear stays and causing the rotor to rub. My steel frame did that...now I'm about to have a brace welded in to try to "cure" that very problem. Typically the hub doesn't flex nearly as much as the rear stays.
    Mike
    I have a new santa cruz heckler with a rp3 rear shock. I ride to work 2 days a week and put slicks on my rims. I never have the rubbing issue with the slicks on. I also put the rp3 pro pedal setting on the firmest setting for the ride to work since it is all pavement. This makes me think that frame flex or the brake cable routing, though I do not understand the physics, is the problem. I also am questioning my skewer. When I mount my mountain tires I have to adjust the skewer a few times before it seems centered and I get no rub on the stand. Though when I mount my slicks and put the rear wheel back on I don't have to adjust the skewer as much to have no rub. I rode to work this morning(slicks and rp3 setting on firmest) with no rubbing but had considerable rear rotor rubbing riding(2.24 front & 2.4 rear tires and rp3 setting on middle)trails this last weekend.

  14. #14
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    Thanks for your input

    Quote Originally Posted by cutthroat
    If the rotor is trued and running smoothly in the stand, and you have a reasonable spacing in the caliper, the issue is not with the brakes. it has to be frame flex, cable compression, loose axle, skewer or some other factor. I note that with my Hayes pads set fairly close to the rotor I can induce that "shing - shing" noise when I take a high G force turn at speed. The wheel itself is flexing under the load and causing the rotor to contact the pads. I run the Avids a bit more open and it doesn't happen with them, but if you hear the noise when you are JRA, you've got some flex related issue to track down. (spoke tension, hub tension, axle play, skewer tightness, inherent frame flex) You can try running the calipers more wide open and compensate for the lever feel by adjusting lever throw, reach and lever leverage - if you have the ability to tune the levers (Avid SD 7s, Ultimates, XTRs)
    cutthroat. I do not mind the occaisional "shing- shing" but the noise I get is more like a hinge that needs oil- a squeaky, creeking like metal on metal sound. My LBS trued my rotor and the sound disappeared but came back after a couple of rides. I think you are on the right path with..."it has to be frame flex, cable compression, loose axle, skewer or some other factor..." I will find a solution because I hate noise on my bike when I am riding!

  15. #15
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    I've got the same issue on my Avid front... seems like every time I take the wheel off for transport the shing-shing comes back I've found that dialing the pads out a bit, cruising the lot and cranking down on the brakes for a few minutes seems to cure it or straighten the rotor out.. then I dial the pads back in until I get them to the feel I like.

    When I initially mount the tire, I spin and listen and no shing. As soon as I get on, the shing returns. Probably the flex issue mentioned above... will cranking up the preload help any, perhaps?

  16. #16
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    Quote Originally Posted by kamikazeB
    I've got the same issue on my Avid front... seems like every time I take the wheel off for transport the shing-shing comes back I've found that dialing the pads out a bit, cruising the lot and cranking down on the brakes for a few minutes seems to cure it or straighten the rotor out.. then I dial the pads back in until I get them to the feel I like.
    If the brake pad is rubbing the disc each time you put back the wheel, maybe a quick nut could help.
    http://www.1upusa.com/quicknuts.html

  17. #17
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    I've never had this issue with my 2 sets of Avids over 3 years on 3 bikes.
    Sounds like a set-up/frame issue or else you're not really getting the rotor true.

    -r

  18. #18
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    I've never had this issue with my 2 sets of Avids over 3 years on 3 bikes.
    I not saying it's not possible, but I do find it hard to believe, maybe you got some cherry Avids? the rotors on Avid mechs get warped soo easy, and I know it's not setup issues or flex in my case- I have one on a Planet X Knifen rigid fork, which is about as stiff as it's gonna get, and I have it setup correctly (business card the caliper, very easy), and it will still rub on hard turns after some riding, but I do have the pads fairly close to the rotor for instant response/lockup (it's on a trials bike). Maybe you set yours up w/ the pads extremely far out from the rotor?? It really doesn't bother me, but both of the Avid mech's I have will develop the "shing-shing", regardless.
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  19. #19
    hands up who wants to die
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    I meant that I've never had an unfixable rubbing issue, as the poster mentioned. I didn't mean to imply that Avids are 100% perfect. Particularly the rear is very easy to maintain for me. However, on my older QR, 30mm stanchion fork, I do get singing on highspeed turns (light wheelset also).

    I've had my share of warped rotors (I use the 185s), but I can get them back into good enough true. I've found the CPS system really easy for getting the caliper aligned well.

    I like some modulation in my braking, so I don't run them set really stiff/close (I don't want them to feel like a Hayes!!), but I can lock front and rear brakes with 1 finger. I think my pads are definitely further away from the rotor than yours. I only weigh 160 w/gear.

    -r

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    No answers to this

    though a lot of theories. I finally gave up and took it in to my LBS. Again, the strange part is that I do not get the "metal on metal" sound when my road tires are mounted and my rear shock is in the stiffest setting. As soon as I put on the mountain tires and adjust the rear shock to a more cushy setting the sound occurs. This is only on the rear brake. I use the same rims so it is not a hub issue. I do not mind the occaisional "shing- shing" sound but the sound I am talking about is worse- almost a metal grinding sound. I will post again after my LBS has done some work on it and I ride to see if the sound goes away. This is a very strange problem because it does not occur during my road rides to work, only when riding the mountain.

  21. #21
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    Quote Originally Posted by scheckler
    though a lot of theories. I finally gave up and took it in to my LBS. Again, the strange part is that I do not get the "metal on metal" sound when my road tires are mounted and my rear shock is in the stiffest setting. As soon as I put on the mountain tires and adjust the rear shock to a more cushy setting the sound occurs. This is only on the rear brake. I use the same rims so it is not a hub issue. I do not mind the occaisional "shing- shing" sound but the sound I am talking about is worse- almost a metal grinding sound. I will post again after my LBS has done some work on it and I ride to see if the sound goes away. This is a very strange problem because it does not occur during my road rides to work, only when riding the mountain.
    Sounds like cable routing to me. With the shock set stiffer the housing does not move much. On a softer setting the housing flexes and affects the brake.

    Make sure the routing is as straight as possible and the housing does not bind as the suspension moves.
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  22. #22
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    That could be

    Quote Originally Posted by shiggy
    Sounds like cable routing to me. With the shock set stiffer the housing does not move much. On a softer setting the housing flexes and affects the brake.

    Make sure the routing is as straight as possible and the housing does not bind as the suspension moves.
    the problem. My rear brake cable does move at times. I notice this more on the trail. There is a place where it bends from the top tube near the seat tube along with the front derailleur cable(it gets caught up with the front derailleur cable) to the mount on the rear swing arm. My bike is a 2005 heckler. The LBS has it and I will get it back tomorrow. I will discuss the rear cable routing with them, as you suggested. I know the LBS real well and have a great relationship with them. I appreciate your knowledge shiggy.
    Last edited by scheckler; 03-11-2005 at 06:44 PM.

  23. #23
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    Quote Originally Posted by scheckler
    the problem. My rear brake cable does move at times. I notice this more on the trail. There is a place where it bends from the top tube near the seat tube along with the front derailleur cable(it gets caught up with the front derailleur cable) to the mount on the rear swing arm. My bike is a 2005 heckler. The LBS has it and I will get it back tomorrow. I will discuss the rear cable routing with them, as you suggested. I know the LBS real well and have a great relationship with them. I appreciate your knowledge shiggy.
    Sometimes you need to get creative with cable routing. My buddy, Sparty, did this on his Cake.
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  24. #24
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    looks like Sparty is a tall dude! Was all the oem cabling routed by the top tube, that would be one nasty kink going form the seattube to the seatstays. Where is the cable for the front derailleur, sorry, I'm not familiar w/ Cakes, and I can't see it in the pic.
    btw- Nice Kooka cranks!

    edit: oops, my bad, looks like those Kooka cranks only have one chainring, why is the F der. still on there?
    Schralp it Heavy.

  25. #25
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    Quote Originally Posted by BikeSATORI
    looks like Sparty is a tall dude! Was all the oem cabling routed by the top tube, that would be one nasty kink going form the seattube to the seatstays. Where is the cable for the front derailleur, sorry, I'm not familiar w/ Cakes, and I can't see it in the pic.
    btw- Nice Kooka cranks!

    edit: oops, my bad, looks like those Kooka cranks only have one chainring, why is the F der. still on there?
    He is 6'4".
    The stock routing was on the TT.
    Single ring. The derailleur is used as a chain guide.
    Not Kooka cranks. Carumba (sp) Doublebarrel 195mm.
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