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Is this normal for my MTB

DannysgbbDannysgbb Posts: 15
edited October 2018 in MTB workshop & tech
When i turn my bike upside down, put it into 10th gear and spin the peadals so the back wheel go's really fast the bike shakes a bit. Is this normal?

Posts

  • 02GF7402GF74 Posts: 1,294
    By 10th gear you mean the smallest sprocket?..
    . I'm just about to wash my bike so if I remember, will give that a go... In theory since bike wheels aren't balanced like car wheels are, and that the valve will be the heaviest part of the wheel, I would expect some but not a whole lot of shaking going on
  • JGTRJGTR Posts: 1,404
    No it’s not normal to turn your bike upside-down and spin the pedals really fast......unless you are 6.
  • 02GF7402GF74 Posts: 1,294
    Spinning as fast as I can in 11th (smallest sprocket) I can feel a tiny bit of vibration but it's not s if the bike is jumping off the ground, so nothing to worry about......

    Also I you have sealant in the tyre, then after periods of no use, it will dry out in one spot.
    .. If your vibrations aren't good, mark the tyre and fit it in a different position and see if that helps
  • That sounds like the rear wheel is out of balance. But....

    # Tyres are moulded components and are not machined items in perfect balance. There is nothing you can do about that. If it is really bad, take it back to the shop you bought the tyre from, otherwise either live with it or scrap it.
    # In addition, they may not have been fitted correctly.
    # Also, as has been mentioned already, any sealant may not have had time ot distribute itself evenly. Once you get going on the trail, that will sort itself out.

    All these things will put the wheel out of balance.

    The only one you can do something about is the tyre fitting. Look closely at where the tyre meets the rim, just above the rim, you should see a moulded line in the tyre wall that should run 1-3 mm away from the rim, but whatever the dimension, it should be parallel! To get it parallel there are two methods. One is to inflate the tyre to about 60 psi. This may force the tyre into the correct position, you may hear a bang, or not. If that doesn't work, try method number two.

    Remove the wheel from the bike and let out a lot of air, maybe down to 5-10psi. It should be enough to keep the tyre on the wheel but still allow you to move the tyre on the wheel. Where the line is closest to the rim hold the tyre in your hands with the side you are working on uppermost. Then wave the wheel up and down, whilst you use the weight of the wheel to move the rubber away from the rim. If it won't move, let some more air out. Repeat.

    Once the lines are parallel, the wheel should spin with the tyre looking more even and stable. Any out of balance forces will have been reduced, but you will never get rid of them completely. MTB tyres are big and lumpy.
  • cooldadcooldad Posts: 32,904
    Yes.
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  • It is fine.
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