Valve stem
A bicycle valve is a check valve on a bicycle tire or tube, that is used for filling the tire with gas, commonly air.
Valve types
A valve is located in a metal pipe, the length of which depends on the profile height of the rim. There are three basic types of bicycle valves.
Dunlop valve
- DV - Dunlop valve
- NV - normal valve
- Bicycle valve
- Express Valve
- Wood valve
- German valve
Rim bore
- ø 8.5 mm
Thread to DIN 7756
- Outside VG 8x32
Maximum pressure
- 6 bar
The Dunlop valve is the most common in Germany, Austria and the Netherlands. It is found mainly in this city and touring bikes and up to the 1980s in almost all types of bicycles. It was named after its inventor John Boyd Dunlop, founder of the tire company of the same name. It is characteristic that the valve is in a piece of pipe and is secured with a nut. The valve can be quickly and change without tools, but also just as easily steal or sabotage. To drain of air, the nut must be loosened.
Dunlop in the original pattern is a valve insert used in the lower portion has a tube which has on the sides through the air holes. Through the pipe, a short rubber tube is pulled, closing the holes. Pumping the pressure of the rubber tube is overcome such that air can flow into the tube. The inflation requires much force, not only the back-pressure to be overcome, but in addition, the rubber needs to be dilated. As improvement, a valve with a ball or cylinder of plastic or metal dar. This allows the hose with significantly less force to inflate. In order to distinguish this variant automatic valve or Dunlop valve was called. The terms Dunlop and Dunlop valve are today used as a synonym. Both types are common, the shape with rubber hose as a check valve, especially in the low-price segment.
Most Dunlop valves are not designed for pressures higher than 6 bar. But there are also versions for much higher pressures.
Since this valve can not be opened without supplying or discharging compressed air, the tire pressure can not be measured but will be more than a rough estimate. In air pump built-in pressure gauge show the pressure only, while air is pumped into the tire and thus the valve is open.
Sclaverandventil
- SV - Sclaverandventil
- Double valve
- Racing valve
- Tubular valve
- Presta valve
Rim bore
- ø 6.5 mm
Maximum pressure
The Sclaverandventil was invented by Frenchman Etienne Sclaverand and is therefore usually called Double valve. The locking device of this valve is similar to a screw with countersunk head. A knurled nut secures the seat and must be loosened for filling.
Once the knurled nut is loosened and is depressed, the valve is open. When pumping only the back pressure in the tire has to be overcome, which makes the pump easily. Outwardly aspiring air, the valve automatically closes. The higher the pressure, the stronger the truncated cone is pressed into its seat. This property make Presta valves suitable for high tire pressure, as is desired in the racing to achieve lower rolling resistance, for example. Presta valves only need a small hole in the rim, they are therefore also suitable for narrow rims.
Even with wider rim is a small bore is advantageous because this also means a stronger rim stability. Therefore Presta valves are now spread even to mountain bikes. For most bicycle inner tubes, the valve is screwed into the metal pipe and can be replaced with a suitable tool.
A pressure gauge for fitting on the valve opens it mechanically, and the tire pressure can be measured.
Presta valves are mechanically stable than some other valves. The threaded shaft with its knurled nut, for example, bend slightly at inept up or discontinuation of the pump.
Very similar to the Sclaverandventil Regina is the valve that is used mainly in Italy.
Schrader valve
- AV - Car Valve
- Car valve
Rim bore
- ø 8.5 mm
Thread to DIN 7756
- Outside VG 8x32
- Inside VG 5x36
Maximum pressure
The invented by August Schrader valve is also used in motor vehicles and therefore also called auto valve. A tire with Schrader valve can be inflated at gas stations, no adapter is required. To inflate with air pumps for Dunlop and Presta valves hoses with auto valve, an adapter with built-in check valve is required.
When attaching the pump head or a pressure gauge, a pin is pushed down in the valve, which opens it. Then measuring the pressure in the tire is made possible. Therefore, hand pumps for car valves require a check valve in the pump head.
With a special valve cap having at the top a screw fitting for valve cores and to put the other way around (so-called key valve cap ), the valve cores from Schrader valves can be installed and removed. The long inserts sometimes do not fit, the brief should always fit (see pictures below). Key Valve caps must be purchased separately for the most part.
Valve adapter
For the different valve types, there are respectively suitable air pump and pressure gauge. Many air pumps are suitable for several types of valves, for example, by variable pump heads. The company alligator has a universal valve based on the flash valve developed that will fit on virtually all valve sticks. The disadvantage is that you can not measure the pressure. With adapters also pump and pressure gauge can be used that do not fit directly to the valve. Are widespread in particular adapters that allow the inflation of Presta and Dunlop valves with Schrader valve pumps, for so the tires can be inflated at petrol stations. A rubber seal on the adapter is required to prevent leakage of the air between the valve and adapter. The figure shows different adapter. Left to right ( → pump valve ):
Valve inserts
Dunlop valve with ball (lightning valve )
Sclaverandventil
Sclaverandventil
Regina valve with cap
Regina valve
Schrader valve long
Schrader valve briefly
Schrader valve for tubeless rims (car)
Universal Valve Core of the company Alligator
Designations
The names of the same valves and valve types is slightly different depending on the manufacturer, dealer, or land on the packaging multiple names are usually given. The distribution of each type varies by country, manufacturer and also the type of bike and age.
- Dunlop valve
Bicycle valve, Dunlop valve ( according to John Boyd Dunlop ), Woods valve (after CH Woods ), Netherlands, English
- Express Valve (insert)
Express Valve, patent valve, Automatic, Alligator (among producers )
- Schrader valve
Car valve, Schrader valve ( after August Schrader, New York), Moto (motorcycle), American, MTB
- Sclaverandventil
Sclaverandventil (after Etienne Sclaverand ), Presta valve, french, racing
The word " Presta " and " presto " is French and Italian origin, in addition to the importance (fast, hurry, immediately ) and the reference to the road bike comes optionally also a derivation, a former manufacturer or brand name as the source in question.
- Regina valve