Most Common Types of Inner Tubes: Schrader and Presta
There are two common types of valve stems on bicycles, the Schrader (“American” type) and the Presta (“French” type). The Schrader or American-type valve is common on cars and motorcycles. It is also found on many bicycles. The valve stem is approximately 8mm (5/16?) in diameter and has an internal spring plunger to assist in shutting the valve.
To deflate the Schrader valve tube, it is necessary to stick a small hex wrench or other object into the valve in order to press on the stem and release the air. Upon release of the stem, the stem spring shuts. Schrader compatible pump fittings press on the internal stem with a plunger, allowing the tube to be filled.
The Schrader valve core can be removed if necessary. This is rarely required, but a valve can become stuck and cause a slow leak. A loose core can also be the source of a slow leak. A special tool will remove and or tighten the core.
The Presta or French-type valve is common on mid and higher priced road bikes and on higher priced MTB bikes. Presta stems are nominally 6mm (1/4?) diameter, thinner than Schrader valves. At the top of the stem is a small lock-nut, which must be unthreaded before air can enter the tube. To deflate the inner tube, unthread the locknut. Depress the valve stem to deflate. To inflate the tube, unthread the locknut and tap the valve to insure it is not stuck.
Presta valve tubes come with different length valves. The longer valve stems are needed for the deeper aerodynamic rims.
The rim valve hole should match the valve of the tube. It is possible to use the smaller Presta valve in a rim intended for the larger Schrader by using an adapter sleeve.
Still not sure? Stop by and we will give you a demonstration!