Possible tyre problem

diamondbacker
diamondbacker Posts: 224
edited September 2016 in Workshop
I have recently fitted some Continental 700 x 28 touring plus reflex tyres to my bike. When I raise the rear off the floor and turn the cranks by hand there seems to be a wobble on each rotation as if the tyre is heavier on one side that causes a wobble at speed. The tyre appears to fit correctly and the wheel seems fine too.

Is it normal for a tyre to behave this way, is it dangerous?

Comments

  • mugensi
    mugensi Posts: 559
    No, its not normal. It may, however be the tube causing it. Try a new tube and see if the same happens, if it does, send it back to the retailer and request a warranty replacement.
  • sungod
    sungod Posts: 16,556
    diamondbacker wrote:
    I have recently fitted some Continental 700 x 28 touring plus reflex tyres to my bike. When I raise the rear off the floor and turn the cranks by hand there seems to be a wobble on each rotation as if the tyre is heavier on one side that causes a wobble at speed. The tyre appears to fit correctly and the wheel seems fine too.

    Is it normal for a tyre to behave this way, is it dangerous?

    do you mean the whole bike moves up/down? that is common, due to the imbalance from the valve stem, when the wheel is spinning fast even a few grams will cause this, but when riding it makes no difference

    if you mean the tyre itself is physically wobbling with respect to the rest of the bike, that's another matter
    my bike - faster than god's and twice as shiny
  • keef66
    keef66 Posts: 13,123
    If the tyre is properly seated all round, isn't visibly deformed anywhere and it isn't rubbing the stays / brakes, take it for a ride and see how it feels. If it feels OK to ride you'll be fine
  • diamondbacker
    diamondbacker Posts: 224
    No it's not the tyre that wobbles it's the bike and it is only when the wheel is spinning pretty fast. It feels ok when I'm actually riding it I was just a little paranoid I think.
  • kentphil
    kentphil Posts: 479
    Is the inner tube sat in the wheel rim correctly all the way round? If the inner tube is caught between the rim and tyre it can cause the tyre to bulge slightly.
    1998 Kona Cindercone in singlespeed commute spec
    2013 Cannondale Caadx 1x10
    2004 Giant TCR
  • fenix
    fenix Posts: 5,437
    I think its just the slight imbalance of the valve - only noticeable when you pedal the wheel fast and it's suspended.

    Not an issue in the real world.
  • sungod
    sungod Posts: 16,556
    diamondbacker wrote:
    No it's not the tyre that wobbles it's the bike and it is only when the wheel is spinning pretty fast. It feels ok when I'm actually riding it I was just a little paranoid I think.

    i once went through the physics/maths on this, even a 5g imbalance at high wheel 'speed' results in a force that's significant wrt a road bike's weight, a freely suspended bike can really jump around

    but when you're riding, the system weight now includes you, and also the wheel is being forced into contact with the ground, even on descents at extreme speed this level of imbalance will not be noticed
    my bike - faster than god's and twice as shiny

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