Misshaped inner tubes

chunkymonkey909 Posts: 11
edited October 2008 in Workshop
Recently, when I replaced a couple of inner tubes I noticed that when they were inflated in the tyre it was misshapen around the valve area.
If you look at the tyre from the side it dips in so you get a flat spot.
When the tube is removed and inflated its like theres not enough rubber around the valve area causing a constriction.
Surly this is not good as you will be riding on a wheel that is not completely round?
I can't feel the flat spot when I ride but it must have an effect that is greater than using different brands of tyre or different pressures?
Is this normal?


  • gkerr4
    gkerr4 Posts: 3,408
    it won't be mishapen when it is inside your tyre don't worry.

    there isn't the room in there for it to 'bulge' in the bigger areas so it will rapidly swell to the exact shape and size of the inside of the tyre / wheelrim - and then provide pressure in all directions.

    don't worry about it - honest.
  • System_1
    System_1 Posts: 513
    Are you using the correct size tube. For instance if you are using 32mm tyres and a 21-25mm innertube you could have problems like you describe.
  • andy_wrx
    andy_wrx Posts: 3,396
    If you inflate an innertube outside the tyre, it will go the most remarkable shape if you inflate it to the thickess of your arm.
    It will bulge in places where the rubber is thinnest and have constrictions areound the valve and where the two ends are joined together.
    But inside the tyre it hasn't room to do any of this.

    Like GKerr says, it's fine, it's normal
  • Thanks for the replies. I'll stop worrying about inner tubes and worry about something else :-)