When I try to pump my bike tires (Dunlop valves), the valves resist letting air in. It's as if I'm trying to pump air through a blocked valve. If I push really hard and I have a lucky day, something inside gives way and the valve starts working normally, inflating the tire.

Some weeks later, the problem is back to square one and I have to perform the procedure again. I have tried at least three different pump brands. Outside temperature is around 10 degrees Celsius. My hardware is not very old, one or two years, and I have 4 tires with this problem.

Is there something simple I can do to remedy the problem? I'd like to avoid replacing inner tubes and valves if possible.

  • @Criggie: The valves are 1-2 years old. In the region I'm located Dunlop valves are the dominating valve type and widely available. Other types of valves can only be found in specialty stores. – Gruber Mar 23 '17 at 10:08
  • @Gruber there are two types of Dunlop valves. The older type has a little rubber hose that is pushed against the stem to seal it. The other type is more sophisticated, where a small rubber ball in a housing seals the valve. These are often called 'Blitzventil' in German speaking countries. – gschenk Mar 23 '17 at 12:54
  • Why not replace the valve, they are easy to get and cost pennies. They tend to fail long before the inner tubes, and since they are so ubiquitous. – gschenk Mar 23 '17 at 12:55
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    @Criggie a Presta valve's stem is not as wide as a Dunlop valves. To fit a a shim or adaptor would be needed. Which would not make much sense, since Dunlops are in half of Europe much cheaper and easier to get. – gschenk Mar 23 '17 at 13:04
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    @gschenk You are correct - dunlop/woods valves use a 8mm rim hole, same as schrader valves. Presta use a 6mm rim hole. My earlier suggestion was wrong. – Criggie Mar 23 '17 at 22:12

There are two types of Dunlop (or English) valves. I shall come back to these below. All valves have commonalities.

First of all, one has to overcome the pressure in the tire before air flows into it. Unlike the valves on a car, the valves on bicycles are check valves that are held close by a higher pressure on the inside. When you pump, you will sense that the pressure builds up in the pump, its hose, etc, until suddenly the valve opens and the air streaming in may be heard.

Any valve may also have dirt or other objects in side, check if your valves are clean. You can remove Dunlop valves and wash them in water with a small amount of dish-washing soap.

Old Type

The higher pressure in the tire pushes as rubber hose against a hole in the valves stem, sealing it. This type of valve is now uncommon in most of Europe, but may still be found on older bikes or, for instance, in China.

Dunlop valve, old type (CC-By-Sa Andi58456 via Wikimedia)

The rubber hose may degrade. This typically leads to the tire leaking. That it sticks to the hole is conceivable. Tire repair kits often have these little hoses included. In a pinch they allow for quite a lot of improvisation. Otherwise they ought to be replaced with the new type.

It is conceivable that the rubber hose is very tight and that you have to blow it up like a balloon first. However, that is just a wild guess. I have thrown these valves right away when I found one in an old bike.

New Type

A small rubber or metal ball inside a ferrule is pushed by the internal pressure up against the valves opening. A very common type of valve in parts of Europe. This type of valve is often called a Blitzventil in German speaking countries.

Dunlop valve, new type (CC-By-Sa Andi58456 via Wikimedia)

This valve is somewhat susceptible to dirt, and ought to be used with its cap only. Usually dirt will prevent proper seal such that the valve leaks a little. Oil, grease, or harsh detergents may foul valves with a small rubber ball. It is conceivable that it gets sticky and clings to the opening.

Some of these valves tend to become slightly harder to open when they were pumped to a high pressure before. In that case the rubber ball is wedge very hard against the valves opening, and it takes more force to push it inside. Since one has also to work against the pressure in the inner tube, it may be significantly harder to pump it up.

In my experience, this is not much of an obstacle it just takes one tough pump stroke, and its free. However, your valves might be worse in that regard. If cleaning doesn't help, consider replacing the valves with other Dunlop valves. They cost about 0.5 Euro a piece.

  • Excellent answer. Looking at the pictures, I can conclude I have the new type. I may have a dirt problem with the metal ball inside. – Gruber Mar 23 '17 at 15:09
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    John Dunlop was born in Scotland and lived most of his life in Ireland. I'm sure he'd be delighted that people refer to his valves as "English". – David Richerby Mar 24 '17 at 11:38

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