Originally Posted by
cyccommute
Yes, the Presta stem sometimes pulls out of the tube but I’ve also seen tons of Schrader fail at the valve stem. The rubber coating fo the Schrader valve gets cut and it won’t hold air. The stem can get cut when the Schrader valve is at an angle in the valve hole of the rim. Sometimes that’s because people don’t install the valve correctly and leave it at an angle and sometimes it’s due to creep of the tube when the pressure is low. Oddly enough, I’ve never seen a Presta installed at an angle or at an angle due to tube creep.
The Presta and Schrader valves I've seen are attached differently, the Presta has a groove in the metal stem while the Schrader has an integral rubber circle which in my opinion is stronger due to the bigger attachment area. But yes, I've seen Schrader fail due to tire creep. A friend of mine had this problem on his front wheel, braking on descents with a heavy loaded bike. Tried many things but the only way to really fix it was to change the rim.