[Grenouille]

Any tips/tricks for figuring out what caused a flat, when you're out on the road? When there's no obvious nail/glass/whatever sticking in the tire? And you dont have e.g. sink handy to immerse the tube in to look for leaks? And you've felt all around inside the tire and found nothing?

(yeah, a bit of frustration with this question....)

[BobH]

Well, that sounds like me a few weeks ago, but I was at home. Just a thought, air up the tube and go all the way around it with a wet hand. When you get over the leak, part of your hand should feel some evaporation.

BobH.

[rola643]

Sure it's not leaking from the core of your stem? If you don't have a sink try a bottle of soapy water.

[photosbymark]

Well if the tube is out of the tire, you can try inflating it again there with some pressure. When its not on the wheel, just about anything can be used as a dunk tank if you need to. Yet without the confinement of the wheel and tire, in my experience it usually shows itself. Soapy water and looking for bubbles is also good. IF you don't see obvious damage, the valve stem is the first place to start. Its likely either the stem itself or sometimes the stem gets cut where it goes into the wheel. Rola knows flats.

[LarryM]

One thing that almost always works for me is to pump up the tube a bit and run it around very close to my ear. Even if I can't hear the leak I can almost always feel the escaping air on my ear.

As for finding the thing in the tire or on the rim that caused the flat, I mount my tires with the tire label next to the valve hole. Once I find the leak in the tube and know that it is e.g. 4 spokes forward of the valve, that's where I start looking for the object.

If you can't find the cause in the tire, check the rim tape and spoke ends.

If there are two small holes in the tube, characteristic of a "snake bite" or pinch flat, there won't be any foreign object to find.

[j3rd]

I carry a spare tube and look for the hole when I get home. In the rare case that I get two flats, inflating the tube and holding it by your ear or cheek to feel the leak works pretty good.

[Ecospeeder]

I went thru that with my new bike. The tire was too limpy to stay beaded on the rim over bumps.