Originally Posted by
Miele Man
Sometimes you get a thorn or a thin piece of wire that ONLY goes through the tire when weight is on the wheels. In such a case it can be quite hard to find the item that's causing the flats. I take the tire completely off the rim and then flex the tire and run a cotton ball along the inside of the tire and hope it snags on whatever has punctured the tire. Sometimes I've had to do the same thing on the outside of the tire because the thin wire is protruding a bit on the outside but doesn't work its way through to the tube until after some distance riding.
Cheers
Great advice. This has been my experience as well. Little shards of glass and metal pieces like staples and pushpins get in the tread. Removing the tire and flexing it will eventually find these little buggers. Double flatting after you have swapped tubes without finding the cause is a tell tale sign you have some tiny piece embedded in the tire.