XC3 rear wheel noise/wobble – advice please…

Forums Mountain Bike Forum XC3 rear wheel noise/wobble – advice please…

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    • #127250


      I have a used GT Agressor XC3 mountain bike which needs some tlc to get it back into use.
      I have cleaned it, oiled it and replaced the rear derailleur cable and done minor adjustments.

      I would like to ask for your advice on some rear wheel/cog noise & wobble I am experiencing – see video in following link; [url:14ap8zkl]https://youtu.be/3wvSo2pd8tI[/url:14ap8zkl]

      When I pedal it up it doesn’t sound too bad – when I stop pedalling and the wheel spins;
      1. There is a loud/varying rumbling/vibration.
      2. There is wobble visible on the tyre which looks excessive.
      3. There is some wobble/vibration visible on the cog.

      What is causing this/should I be checking?
      I am handy with a spanner and would like to get this bike back to full working order for light occasional use.
      I’m not looking to spend a lot or upgrade components.



    • #127251

      The wobble you see in the tire looks like your rear wheel is bent out of shape a bit. Nothing major. True it up with a spoke wrench or have a local bike shop do it if you’re not comfortable with it. Every rear cog "cassette" I’ve ever had, had a little wobble to it. No worries there. As far as noise goes, I would clean and re-lube your rear hub bearings. Maybe have your lbs clean and lube the pawls inside your cassette. Also, sounds like your rotor is dragging against the brake caliper. Give that some adjustments.

    • #127252

      Thanks for your reply.

      I have dismantled the rear axle, cleaned and reassembled and the noise seems a bit better.

      There is wear on the cassette side inner bearing surface and some of the bearings, the cones look ok;
      Disc side – looks ok
      Cassette side – wear on surface
      Cassette side bearings – wear on some

      Is the cassette side inner bearing surface replaceable on its own and what is the correct part name?

      I have taken it for a test ride and the rear gears skip a lot so I will be adjusting them but also the front brake;

      1. When applied the tyre/wheel moves to the left (caliper side) – is this normal?
      2. I can’t get it to lock up and the adjustment screw (at lever) is all the way out – is it ok to undo the cable holder on the caliper and pull it in or has the cable stretched and should be replaced?



    • #127253

      Hi there Mark,

      The galling you see in the bearing cup should not be bad enough to cause you to replace it. Repacking the bearings should get you a good rolling wheel again.

      As for wobble at the hub(signaled by non-cyclic brake rub and play upon moving the wheel left to right), you should be able to get rid of that by properly adjusting the double-nuts on the axles. You tighten the inner nuts until all wobble is gone, but the wheel still rolls freely and then while keeping them in place, tighten the outer nut to capture it and keep it from backing off. If you don’t have wrenches skinny enough to keep the inner in place, you can loosen it a little and then tighten the outer over it, trying to stop when the inner is back at it’s intended location for proper adjustment.

      As for adjusting the brake, back off the adjusters all the way, pull more cable through at the caliper to tighten and then use the adjusters to fine tune the brake.

      It is not normal for the wheel to move in any direction when the brake is applied. It should be like the rear, unable to shift in either direction when properly adjusted.

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