I've been having problems with the presta valve cores failing. Usually
the bike is just sitting home when it happens. Sometimes the tire goes
flat sitting over night, sometimes it goes right after pumping up the
tire. A couple times the rubber at the base of the stem tears, but
usually it is the valve itself. I've checked by putting a little air in
and holding it under water and watch the bubbles.
I used to use Continental tubes, which have a removable core. All of
them have eventually failed, usually lasting about 1 year. My last one
failed a couple days ago.
I got 2 Trek/Bontrager tubes (with removable cores). The first I tried
was bad out of the box, the 2nd was ok.
I have 2 Salsa tubes, which don't have removable cores, they have been
ok so far. one has been on the bike since about early spring, the other
is still in the box.
So far my score for flats is:
Running over something pointy: 0
Spokes puncturing from the inside: 1
Valve stem tearing: 2 or 3
Valve cores failing: too many to count
Any suggestions for a reliable tube?
Thanks.