Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 29 Post(s)
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Before cooling for a complicated reason follow Danno's advice and check the rim and tire carefully in the area that your punctures are occuring. Also learn to make a reference mark on the tire at the valve (or mount with a label lined up), so you can quickly line the tire and tube to check for possible causes.
If you can't find any burrs, exposed spoke holes, or rough spots it might be a narrow rim issue, though it's odd that your problems occur in the same place (unless you mean on the belly side generally)
One problem of super narrow rims is that the inner walls of the tire come close together forming a space that's sort of an hourglass shape in cross section. When the tube is inflated it first fills the tire section, then with friction holding it against the walls of the tire, the small section stretched across the gap blows out like a bubble and fills the section in the rim. (Draw yourself a small x-section sketch if you can't visualize it)
As a result the tube material stretches 2-4 times more in that narrow zone than anywhere else and is prone to being over stretched and failing. It's especially a problem if you installed the tube with a twist.
There's no sure cure, but here are a few hints.
1- Buy decent quality tubes, they're more uniformly made, and less likely to fail from overstretching. You don't have to go first class, but try to stick with decent brand name tubes like Kenda, or IRC, as opposed to house brands or even bike company brands. Manufacturers are more likely to pay attention to quality when their own name is on the box.
2- buy the right size tube, preferably the largest width that's less than the tire. ie for your 25mm tires a 23mm tube is a better bet than a 20mm
3- inflate the tube to a sausage shape and rub it liberally with talc which will help it slide within the tire.
4- stuff the sausage well up into the tire avoiding twists and stretched or bunched zones
5- mount the tire, letting enough air of the tube to make the job easy, but not enough for it to lose it's sausage shape.
6- finish by pushing the valve up into the tire taking any part of the tube that may be trapped under the tire, then pulling it fully down to the rim, working it's base past the tight spot.
Starting with decent tubes, and installing them carefully, you should be able to put this behind you for good and get flatsm in the tread area like the rest of us.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance
Last edited by FBinNY; 08-16-10 at 07:30 AM.