bobbyl1966

I have fulcrum racing 7 wheels i had spesialized tires. But the tires had cracks. I start replace the front tire. With kenda tire. Is very hard to install on the rim finally i do. But when i put air the tire say 100 psi when i was in 90 psi the innertube busted in the valeve stem. what is can be wrong. Also same happens yesterday i my other road bike have matrix wheels. The innertube busted in the valve stem again. What is can be wrong. also my fulcrum racing 7 wheels i have put new rim tape but is moving is left uncover the spokes holes. How i fix that problem.

sch

Possible too much of an angle of the stem at the hole, but in general tube failure at the valve is not an unusual cause of tube failures,
IME it is the most common cause of catastrophic tube failure. When putting a tire on, I find it best to start at the valve making sure
the valve is straight and pushed into the rim as far as it will go and seating the tire bead into the rim then working around the rim
while periodically checking the valve is still straight. Some tire/rim combos are difficult to mount, this can be learned only by experience.
Lubing the rim edge with liquid soap can help install, but removing said tire in the field can be even more problematic. Rims come in
different widths as does rimtape, you may have too narrow a tape for the rim. The opposite can occur with too wide a rim tape with
the tape getting up where the tire bead sits and causing tire to lift off the rim when inflated.

Here is a discussion of rimtape width from 2006: https://www.bikeforums.net/bicycle-me...ape-width.html

speedy25

On a recent group ride there was a tandem that had blown 2 innertubes and both were at the valve stem. An inspection by another rider found a BAD burr around the valve stem hole. Make sure yours is smooth with no sharp metal edges.

-SP

(PS- Add your location to your info. I suspect English isnt your native language. )

cny-bikeman

If the tire blew out with a bang you probably did not get all of the tube under the tire bead and the tube then pushed the tire off the rim. You can also get a problem if using narrow rims and the stem is not all the way seated in the valve hole - then you often get a crescent shaped (curved) hole or a blister next to the valve stem.

In almost all cases it is best NOT to start at the stem/valve hole, but rather to finish close to there. It's much easier to get the tire on the rim because you can push the bead toward the center of the rim where the diameter is less. When the tire is all the way on the rim push the valve stem up into the tire, push the tire down onto the rim, and then gently but firmly pull the stem back out again. When inflating observe the tire's bead line (raised ridge of rubber next to the rim) and if it is further away from the rim at any point deflate the tire and check to make sure there is no part of the tube under the bead.