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I've recently changed the default 700x35 tires and 35mm Schrader inner tube to 700x25 slicks with 25mm Presta inner tubes.

However whilst fitting the new tire and inner tube, I noticed that the inner tube had about an inch or two of excess length to it. This mean I had to tuck it into the tire, doubled back on itself.

I've doubled checked the inner tube packaging and it's definitively for a 700 diameter rim.

I presumed that it would sort itself out when I pumped up the tires. Is this normal?

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I've had this happen, and my solution was to distribute the excess throughout the circumference of the tire. While I didn't notice any problems due to this, my tires aren't nearly as thin as 700x25; I can see those being more finicky. (Not an answer because this is speculation.) –  Neil Fein Jun 24 '11 at 16:46

4 Answers 4

up vote 9 down vote accepted

A tube should not have excess length, and doubling on itself will cause the tire to feel uneven while riding, as well as increase the likelihood of flats.

Assuming the tube is the correct size for the tire, as you said it was, there are 2 common causes for this problem.

  1. If you installed the tube without inflating it first, just a tiny amount, then it hasn't got the shape to sit in the tire completely, and it will appear to be too long. It isn't, just add enough air to the tube to give it a little shape and try it again.

  2. If you did that already, then in the process of inflating the tube to make easier to install in the tire, you have probably inflated it too much, and so it has gotten larger. It's not permanent, just let the air out and inflate it only enough to give it shape before installing it in the tire.

If these don't work, there is likely a problem in manufacturing, and you should get the tube exchanged.

Hope that helps.

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I've personally seen a tube too-long when not inflated, turn into "perfect fit" with just a bit of air in it; just enough air to give it a circular shape if you lay it on the floor. I just blow lightly into the open presta valve - no need to use a pump.

And push the tube into the cavity of the tire, don't try to "seat" it on the rim. (caveat: my experience is with larger MTB tubes & tires)

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This is exactly what I was talking about in the first half of the answer above. +1 for agreeing with ME. ;) –  zenbike Jun 27 '11 at 13:08
    
Yes, and I already +1'd you for it :-) I would have just added my comment to your answer if I could at the time. –  Joe Bronikowski Jun 27 '11 at 21:54

It isn't normal, and will cause a problem. Tubes only expand when you put air in them, and will never get shorter. I'd try a different brand of tubes.

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Some (many) tubes are made to fit too wide a range of tire sizes and will tend to be a bit on the long side inside some tires. One should make a point to only inflate the tube enough to fill it out before installing (so as not to stretch it further), then make sure during installation that it's not buckled or doubled on itself at any point inside the tire.

If the tube is buckled/doubled anywhere not only will you have a "lump" while riding, you'll also have a flat tire in a few dozen miles of riding.

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