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  1. #1
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    Tyre problems - they're not round

    Hi, this is my first post and i know little about bikes.

    I've got a fairly old (3 years) mountain bike, with the full knobblies, I need to start commuting on bike so i want to switch to slicks and if i'm fairly fast i might buy a road bike. I bought some slicks (and smaller inner tubes too) and tried to put them on, everything went smoothly, tyres on, I went for a test ride and found that every time the tyres go round, I feel a bump. On closer inspection it seems like both of the tyres aren't being pushed out enough so the rims and the tyres arent hooking properly, instead the rims are rubbing against the side walls at those points.

    This has happened to both front and rear tyres and i've tried several tyres to take them off and put them back on. It seems to happen furthest from the valve but not 100% sure about that.

    Any help would be much appreciated.

  2. #2
    cyclist/gearhead/cycli... moxfyre's Avatar
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    Quote Originally Posted by pedal faster
    Hi, this is my first post and i know little about bikes.

    I've got a fairly old (3 years) mountain bike, with the full knobblies, I need to start commuting on bike so i want to switch to slicks and if i'm fairly fast i might buy a road bike. I bought some slicks (and smaller inner tubes too) and tried to put them on, everything went smoothly, tyres on, I went for a test ride and found that every time the tyres go round, I feel a bump. On closer inspection it seems like both of the tyres aren't being pushed out enough so the rims and the tyres arent hooking properly, instead the rims are rubbing against the side walls at those points.

    This has happened to both front and rear tyres and i've tried several tyres to take them off and put them back on. It seems to happen furthest from the valve but not 100% sure about that.

    Any help would be much appreciated.
    Some cheap tires just aren't very round to begin with. Usually the bump is small enough that you can't feel it and it can be ignored for commuting use.

    Your problem may be that the inner tube is bunched up under the bead (edge) of the tire. This is bad not only because of the bumping, but because you greatly increase your chance of pinching the tube between the tire and the rim, which will cause a flat. The best way to fix this is to inflate the inner tube SLIGHTLY (until it can just barely hold its shape) while mounting the tire on the rim.

    If that doesn't work, your problem may be that the wheel itself is not round. Try spinning the wheel with no tire and watch very carefully: does the rim itself appear to be wobbling up and down? If so, you need to get your wheel trued, which involves adjusting the spoke tensions. Mountain bike wheels can go out of true if they've been subjected to very large stresses. Cheap wheels of all kinds tend to go out of true rather quickly, while well-built wheels can hold their true for years.
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  3. #3
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    Make sure you're not pinching the tube under the bead of the tire. Is the flat spot in the last place you pushed the tire into the rim? That's where it's hardest to keep the tube out from under the bead.

    Inflate the tube a little when installing the tire to keep it away from the hook and bead, and once you've got the tire on, go around the entire rim and wiggle the tire back and forth to free everything up. Then pump it up a little, let all the air out, and pump it up full.

    That's my guess, although usually when you pinch the tube it goes flat within the first mile, or even before you fully inflate it.

  4. #4
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    Cheap tires will never seat well.....

    Try 409 or Fantastik spray on the bead....

    Make sure the tube is the proper size for the tire....

    Make sure the rim strip is centered and not over to one side preventing the bead from seating.

  5. #5
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by pedal faster
    This has happened to both front and rear tyres and i've tried several tyres to take them off and put them back on. It seems to happen furthest from the valve but not 100% sure about that.
    Try this:

    After you get the tires onto the rim but before you try to inflate them, push your valve stem in toward the hub. What you are trying to do is to push the thicker area of the tube that surrounds the valve stem inward so that the tire beads don't rest on top of it. When that happens it pushes the whole tire so that it's not concentric with the rim and hub and the high spot will be opposite the valve stem just as you are reporting. As you inflate the tube the air pressure will push the valve stem back out, but by that time the thick part of the tube will be safely out from under the tire beads.

  6. #6
    Senior Member DannoXYZ's Avatar
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    Yeah, my bet's on a pinched tube somewhere that's causing this. Be sure to never install a tube flat, pump it up so that it's round. Insert one bead of tyre onto rim, then install the tube, and install the remaining bead BY HAND. Once the tire's fully on, push up on the valve-stem into the tyre to make sure it's fully inside the tyre. Inspect the seating of the tyre all around making sure it's even, pull up on spots that's sunken into the rim so that they're all even. Then push in on the sidewall so that you can see down between the rim-edge and tyre bead to ensure that there's no tube peaking out. Gently pump up the tyre, making sure no spot starts bulging. That's it.

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