Chapter 3: inspection, adjustment, and lubrication

Valve types

There are two styles of valves used on Trek bicycles (Figure 1), which use different techniques for inflation:

Schraeder valve

Remove the valve cap, attach an air pump with a Schraeder fitting, and inflate. Put the cap back on, as the cap keeps dirt and debris out of the valve. On tricycles, leave the valve caps off. Valve caps are a choking hazard for children under two years of age.

Presta valve

This is also known as a French valve.

Remove the valve cap, if present. Presta valves seal very tightly, and require a lot of pressure to open them initially, so after unscrewing the valve nut, depress the nut with your finger to open the valve. This should let a little air out. Inflate using a Presta valve fitting. After inflation, tighten the valve nut against the valve stem until finger-tight. This provides the same function as the valve cap on a Schraeder valve.

Presta valve stem extension

Some wheels have tall rims. With this rim design, a valve stem extension (Figure 2) is required to inflate the inner tube. Follow the presta valve instructions, but thread the extension on before attaching the pump. After inflation, remove the extension and tighten the valve nut. To keep the extension in a convenient location, the extension can be re-attached to the valve stem after the nut is tightened.