Über Fahrradschläuche: Unterschied zwischen den Versionen

[This section by John Allen]

Because a tire's outer diameter is greater than the rim's, a flat tire "creeps" forward (!) as the bicycle is rolled, and pulls the inner tube with it -- except the valve, caught in the valve hole. With a double-wall rim or a valve stem secured by a jam nut, the tube will only bunch up behind the valve. With a single-wall rim, the valve stem increasingly leans backward. You need only roll a bicycle a few feet for this to happen. Assuming that the inner tube is still intact, you may be able to rearrange the inner tube by rolling the bicycle backwards before inflating the tire. Once done, push the tire sidewalls in all around and take a look to check that the tube is intact and seated properly inside the tire.