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Trek District - grinding noises

tomwardilltomwardill Posts: 21
edited November 2011 in The workshop
Hi all,

I commute on a Trek District, with the Gates Belt Drive.

Recently it's started making a grinding noise while pedalling, it started only when it was wet and I was pedalling hard, but it's since moved on to be most of the time.

It happens at roughly the same point in the pedal rotation, but doesn't appear present if I take the belt off and just spin the pedals.

Any ideas as to likely cause?
Bottom Bracket?

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    what point of rotation?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Starts with the right pedal roughly at the top, till about quarter of the way round and same on the way back up. Seems to be gradually a bigger 'area', but unsure if that's just me imagining it.
  • nicklousenicklouse Posts: 50,675 Lives Here
    grab the cranks and shake. any movement?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Not that I can feel, can't feel any sideways movement in it.
    This is why I'm quite confused.
  • Bi50NBi50N Posts: 87
    It's almost certainly the belt rubbing against the lip of the front sprocket. It's happening because the belt is not perfectly aligned (and may be a bit too tight).

    Gates have a fairly useful support page:

    http://www.carbondrivesystems.com/support.php

    I'm guessing this is the Q/A you need:

    My drive is squeaking or making noise, what’s the cause, and how do I fix it?

    The belt can make noise when forced to run hard against the flanges on the sprockets. This can be due to sprocket misalignment, wheel misalignment, or run out in the drive caused by damaged components. Spraying water on the belt may quiet the drive for a few minutes, but the permanent solution is to correct the alignment or replace the damaged components. Another possible source of noise is a loose front sprocket. Using thread lock on the sprocket bolts alleviates this problem.

    In some cases, the noise can occur when riding in dirty conditions, particularly when mountain biking if grit and water temporarily stick to the belt. This noise in no way indicates a problem with your Gates Carbon Drive. In most cases simply hosing off the belt and pulleys after a ride will end the noise. If noise persists, the solution is simple: spray the belt with water, wait for it to dry, and apply a thin coating of dry silicone spray to the tooth side of the belt. Dry silicone dries instantly, helps shed grit, and does not affect the longevity of the belt. We recommend this product.


    This video shows how to get the belt aligned:

    http://www.youtube.com/watch_popup?v=YS_nO79_7ws&vq=small

    On the District, this means you need to remove, re-fit and re-align the two triangles that connect the split seat and chain stays. If you don't feel confident, take it to your LBS. I find a lot of shops are not that familiar with belt drives, but Action Bikes next to Embankment station has a guy working there who knows his stuff.
  • That sounds exactly like my problem.

    Thanks a lot for the information, I'll give it a try.
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