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  1. #1
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    A couple issues with recent purchase

    Hi All, I just picked up a 2011 Trek 4300 Disc, it is in very good shape visually and looks barely ridden. Got back from my first ride and have found two issues that I'm hoping to get help with.

    1. The rear disc brake,(Promax DSK-907 hydraulic disc brakes), vibrates the whole back of the bike, bad, when medium braking. This is my first experience with disc brakes, on a bike. The disc is not noticeably out of round, that I can see or feel. The front brake is smooth as silk.

    2. The front shock, (Spinner 300 w/coil spring, preload, hydraulic lockout, 100mm travel), clunks on the rebound. Hard to explain, say you pull the front wheel up to hop over a limb or something and the wheel rebounds from it's somewhat compressed state and just hits the end of the fork without being slowed. Does that make sense?

  2. #2
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    For the brakes, make sure everything is tight back there.

    For the fork, not sure there is anyting to be checked. You have a fork with no rebound damper, so no rebound-damping is going to take place.

    It's that whole "you get what you pay for" thing. Best bet is to ride your bike, enjoy it, and save up for a better bike with better components when the money allows for it.
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  3. #3
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    i have same model/year, bought it as i was getting into mtb after hanging up the mx boots. i had issues with my brakes as well, like net wurker said check the tightness on everything. my disc had worked its way loose. the fork, thats the way it is.....i upgraded to a fuel this year as i didnt see the sense in upgrading the frame.

  4. #4
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    Quote Originally Posted by net wurker View Post
    For the brakes, make sure everything is tight back there.

    For the fork, not sure there is anyting to be checked. You have a fork with no rebound damper, so no rebound-damping is going to take place.

    It's that whole "you get what you pay for" thing. Best bet is to ride your bike, enjoy it, and save up for a better bike with better components when the money allows for it.
    ^^^This for the fork, it's topping out and with no rebound dampeener there is nothing you can do. The brake issue is just going to be a process of elimination. Try something if it doesn't fix it try something else until you figure it out. Good luck!
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  5. #5
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    Still having problems with these back brakes. I was playing around with it, checking everything for tightness, no joy. Kept fooling around with them till I screwed up and let air into the system. Looked around a while for a bleed kit but could not find one explicitly for these brakes. Since I was not sure if I was even going to keep them, I brought it to a LBS. He bled the brake fine and cleaned the rotor, all seemed well in my 3 stop test ride so I thought the problem was solved. First ride after bringing it home and it is doing it again, severe vibration running right up the seat post!

    Like others have mentioned, just a process of elimination, LBS suggested changing out the pads first. So in that vain, does anybody see a problem with swapping the rear pads with the fronts and give that a go?

  6. #6
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    The only way to know if your rotor is slightly warped is to pull it off the bike and put it on something that is perfectly flat. A window works great. Lay it on your flat surface and look for any gaps. Hope you get your brakes working.

  7. #7
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    Quote Originally Posted by ironbrewer View Post
    The only way to know if your rotor is slightly warped is to pull it off the bike and put it on something that is perfectly flat. A window works great. Lay it on your flat surface and look for any gaps. Hope you get your brakes working.
    Ummm...no. You just spin the wheel and see if the rotor wobbles in the caliper. Only matters that the rotor is flat (true) when mounted on the bike, not when laying on a table.
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  8. #8
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    Quote Originally Posted by ironbrewer View Post
    The only way to know if your rotor is slightly warped is to pull it off the bike and put it on something that is perfectly flat. A window works great. Lay it on your flat surface and look for any gaps. Hope you get your brakes working.
    I would think the LBS would of mentioned if the rotor was warped, to me it looks just fine.

    I suppose I could swap the rotors front to back as well, in one of my tests.

  9. #9
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    Have you aligned the caliper in the rear? If its way out of alignment it could be the cause. It's prett quick, loosen the bolts that hold the caliper on, squeeze and hold the rear brake and tighten the bolts while still holding the brake.

  10. #10
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    Quote Originally Posted by ironbrewer View Post
    The only way to know if your rotor is slightly warped is to pull it off the bike and put it on something that is perfectly flat. A window works great. Lay it on your flat surface and look for any gaps. Hope you get your brakes working.



    This is unnecessary, just spin the wheel for a visual check.

  11. #11
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    I'll bet the back rotor and pads have been contaminated at one point.
    Swapping the pads will probably fix it. Make sure the rotor is clean or you could contaminate the front pads - and you could contaminate the front rotor with the rear pads.

    The rotor should be cleaned with alcohol or brake cleaner.

  12. #12
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    Quote Originally Posted by patrick2cents View Post
    Have you aligned the caliper in the rear? If its way out of alignment it could be the cause. It's prett quick, loosen the bolts that hold the caliper on, squeeze and hold the rear brake and tighten the bolts while still holding the brake.
    Will do, I'll try this first.

    Quote Originally Posted by Slash5 View Post
    I'll bet the back rotor and pads have been contaminated at one point.
    Swapping the pads will probably fix it. Make sure the rotor is clean or you could contaminate the front pads - and you could contaminate the front rotor with the rear pads.

    The rotor should be cleaned with alcohol or brake cleaner.
    I have plenty of brake cleaner, I'll give that a try. The hard part will be not touching the front brake while the suspect rear pads are in there, for my test ride.

  13. #13
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    Alright, let me see if I can remember what I've done recently.

    - Cleaned the rear rotor with brake cleaner
    - Swapped the pads front to back, back to front.
    - rear rotor looks very true to me
    - I performed patrick2cents suggestion

    Still makes the loud embarrassing screeching and uncomfortable vibration, only in the back. May be a little better but not much.

    I read someone elses post, this is a little different than what patrick2cents describes, they said to:

    Loosen the bolts that hold the caliper on, spin the wheel, squeeze and hold the rear brake and tighten the bolts while still holding the brake.

    I will try this method and also swap the rotors from front to back this time. I will also try to create a video of the noise. I'll clamp it to the seat post so I can hear and see if I can see the vibration.

    Any other suggestions will be greatly appreciated.

  14. #14
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    I have created a video, not all that much to look at but you can clearly hear the sound that it's making. In creating the video I found that clamping the gopro to the swing-arm makes the sound go away. Sounds crazy but it did not make the sound when clamped to the swing-arm, when I removed the camera or mounted it to the seat post, the sound came back.


  15. #15
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    Sounds like mis alignment. Some can be a real ***** to get aligned. I have found the squeeze the brakes method does OK but to really get it right you have to do it by sight and feel.

    Hard to tell from the video but it almost looks like the rotor isn't true. If you spin the wheel slowly do you see it oscillate? That would do it for sure.

    Truth is most less expensive and some even expensive brakes make horrible noises. As long as it stops you I wouldn't stress about it too much.

    A couple of other pointers. Learn to brake with your front brake. Don't go OTB but they are much more effective.

    Also you need to point the rear wheels QR pointing back. If you snagged something with it and it came loose that might end up badly.
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  16. #16
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    Dud you try to true your rotor?

    Here's Shiggy (same Shiggy above) showing you how to do it:

  17. #17
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    One of the reasons I created the video was to show how true the rotor is. In my opinion it is true. You can hear, in the the beginning of the video, on the second pass, the pads are slightly dragging. You can hear how true it is in that portion of the clip. You can see the rotor turning also, it is rolling true. Bending the rotor back and forth, by hand, manually, by eye and feel, IMO, is not going to get any better than that.

    I can still move the front rotor to the back and see if it goes away but I think I will pursue the discovery with the camera mount first. I am thinking it's related to that rear cable somehow. I put a couple tie wraps, pinning the cable more securely to the frame there in the back but that did not work. You can see in the picture that rather than securing the cable to the frame, the camera mount is between the cable and the frame, maybe that's it. I can't believe it is the weight of the extra hardware hanging there on the frame but maybe it is that.

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  18. #18
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    Maybe read this thread about fixing the Avid turkey gooble . I think Trek hardtails suffer from this vibration. At least my 6700 does. I went with organic pads to "nearly" eliminate the noise and vibration. But, a few ppl find the method in that thread to work well for them.

  19. #19
    Abby Design & Constructio
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    If you bought the bike from your LBS then take it in and ask them the problem. If it is something little that out of adjustment then they should fix it free.

  20. #20
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    Check to make sure the disc brake mounts are square and true (no paint). Also make sure the rear hub is not loose. +1 on changing brake pads.

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