Monday, August 29, 2016

Flat tires and Defective Inner Tubes

The only responsibility of a tube is to seal air.  If the tube sealed---and later fails---it is not the fault of the tube.  It is either a another puncture or improper installation.  The tire rim interface is designed to hold all the pressure, the tube just seals it.

The classic story---My tube held air for about 10/20 minutes, 3 days, and then it failed, it was a defective tube.  No the installation was improper or the you got a puncture.

The true defective tube failure rate is very close to zero.  All tubes are pressure tested at the factory.  Any true bike professional will tell you the same thing.

The most common causes of tube failure from improper installation come from not getting the valve stem positioned so to not be under stress.  If your stem is coming out at an angle then the base of the stem is not in the right spot and quite likely will go flat.

The second most common problem is not getting all the glass, thorns or whatever penetrated the tire out of the tire.  When brought back up to pressure the tube repunctures.

If you do not get the tire bead to seat properly and the tube squirts out under the bead and goes bang, again this is improper installation, it is also hard on the ears...

Thorn Resistant Tubes
Thorn tubes are very good at resisting flats when properly installed.  These tubes are really thick in the area near the road and thinner near the rim side of the tube.  Thorn tubes are very susceptible to failure at the base of the valve stem.  It is very important to get the stem coming straight out of the rim hole.  I have seen under low inflation the tire and thorn tube can sometimes slip around the rim under hard braking.

Slime Tubes
I prefer Slime tubes to thorn tubes.  Slime tubes will seal back up around a puncture.  With thorns and small penetrations you may need to add a little air but the sealant will usually work great at keeping you from having to patch tubes or replace them.

Base of  the Valve Stem Leaks Especially with Thorn Tubes

It is rarely a tube failure with leaks at the base of the valve stems.  Two potential issues.  The tube is not inflated enough to put pressure on the tire and rim to keep the tire from sliding around the rim when braking .or. the tube was installed and the valve stem was not pointing straight out of the rim putting too much side pressure on the base of the valve stem.


Here is a link to another article on Defective Tubes.