Valve stem
From Wikipedia, the free encyclopedia
A valve stem is the port on a wheel that allows the tire to be pressurized. They are typically spring-loaded devices that admit air when the external pressure is greater than the internal tire pressure to allow filling.
Contents |
[edit] Types of valve stems
[edit] Schrader
The Schrader valve is used on both automobiles and bicycles. Schrader valves are further classified by their material, diameter, length, and shape:
- TR-4 - Straight metal stem (8 mm dia.)
- TR-6 - Straight metal stem (8 mm dia.)
- TR-13 - Straight rubber stem (11.5 mm dia.)
- TR-15 - Straight rubber stem (16 mm dia.)
- TR-87 - Short 90° metal stem (10 mm dia.)
- TR-87C — Tall 90° metal stem (10 mm dia.)
[edit] Presta
The Presta valve is thinner and is typically only found on road bikes and more expensive bicycles because they can take more pressure. They are also known as "Peugeot" valves, because Peugeot bicycles used to be sold with this sort of valve.
[edit] Dunlop (or Woods)
Dunlop valves were once popular in Great Britain and Asia. They are still widely used on 28- and 27-inch tires in many countries (the Netherlands, Germany, Third World) on single-speed bikes for comfort riding in flat terrain.
Their bases are wider than Presta valves, but they can be pumped with Presta pumps. Pumps with a pincher-type connection however are the most common type used: the classic black pumps mounted on a wooden base. The classic pump does not allow for high pressures, 50.0 psi max.
Due to the construction, the Dunlop valve does not check the pressure. The actual valve can be replaced easily, without the need for special tools as with Schrader valves. This also allows use of a wide stem to fill the tube with a sealant that cures leaks while cycling.
[edit] Invisible valves
Invisible tire valves are different in design from traditional tire valves. An inflator stem is not used; instead, a removable cap on a valve stem embedded in the tire rim is fitted, with only the cap visible. When inflating the tire, the cap is first removed, typically with a coin, and then a "portable" dedicated inflator stem is screwed onto the valve stem. Through the inflator the tire is inflated as usual. Invisible valves are simple in appearance, and by removing the inflator stem can improve the balance of whole tire. Currently invisible tire valves are popular in Europe. Recent designs simplify use with some caps designed to be removed by the inflator stem itself, instead of a coin.
