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[Dunlop valves] Why did Presta pump fail?

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[Dunlop valves] Why did Presta pump fail?

Old 09-27-20, 05:38 PM
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Winfried
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[Dunlop valves] Why did Presta pump fail?

Hello,

On a trip, someone punctured her German bike, which had tubes with Dunlop valves, as they often do over there.

I read the tip has the same diameter as Presta valves, but we couldn't pump it up, even by adding a Presta → Schrader adapter.

Is it because the valve was too short? Does it require a specific pump?

Thank you.

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Old 09-27-20, 05:43 PM
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Check to see if the valve has a slot in the top of the presta section. If so it needs to be loosened to fill the tube. Smiles, MH
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Old 09-27-20, 06:14 PM
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I've only ever seen one in the UK.

No wonder the British lost the war of 1812.
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Old 09-27-20, 07:11 PM
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The Dunlop/Woods thread is identical to that in Presta. I pumped tires with Dunlop valves numerous times using Presta pump heads both screw on and clamp on. Given that the connections to the pump are identical, you could not even claim a Presta vs Dunlop head for a pump, since they would need to be identical.

In any case, I think you might have run into another problem. Dunlop vents use a rubber hose that is pulled onto a stem inside the valve. When the rubber ages it may stick to the stem and block air from coming in. Alternatively it may start leaking and not keep the air in. The rubber hose needs to be periodically replaced but you must have a replacement at hand. In areas where Dunlop valves were common, it would be common for seat tool bags to contain a screwdriver, some universal wrench and the rubber hose for the valve.
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Old 09-27-20, 08:02 PM
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Back in the dat Euro patch kits included a short section of rubber tubing to be the replacement valve "seat". One of my bosses would describe it as the brush for the patching glue, rather then take the time to explain what a Woods valve is and why the rubber tubing is needed. Andy
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Old 09-27-20, 08:25 PM
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Originally Posted by Andrew R Stewart View Post
Back in the dat Euro patch kits included a short section of rubber tubing to be the replacement valve "seat". One of my bosses would describe it as the brush for the patching glue, rather then take the time to explain what a Woods valve is and why the rubber tubing is needed. Andy
I haven't bought a REMA patch kit in a few years, but they included the "valve repair" piece of rubber tubing.
I had no idea what it was until i saw a post about it on these forums.
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Old 09-27-20, 08:42 PM
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Growing up in Australia in the 70's, most bikes had these valves and I remember thinking I'd made the big time when my new bike sported modern "car" (Schrader) valves which could be pumped up at any gas station.
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Old 09-28-20, 01:51 AM
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Originally Posted by 2_i View Post
In any case, I think you might have run into another problem. Dunlop vents use a rubber hose that is pulled onto a stem inside the valve. When the rubber ages it may stick to the stem and block air from coming in. Alternatively it may start leaking and not keep the air in. The rubber hose needs to be periodically replaced but you must have a replacement at hand. In areas where Dunlop valves were common, it would be common for seat tool bags to contain a screwdriver, some universal wrench and the rubber hose for the valve.
Interesting. Too bad I didn't have time to try yet a third pump to see if it were due to the pump being "too deep" for that valve, or an old valve that needed replacement. Since the bike is only a few years old and had no air issue, I would guess only some Presta pumps work with Dunlop/Woods valves.

That also explains why Dutch retailer Hema sells "blitz" valves over here (even though Dutch/German bikes are a rarity.)

Out of curiosity, how do you change an old valve?

https://www.hema.com/en-gb/hobby-lei...-41198070.html

Last edited by Winfried; 09-28-20 at 01:54 AM.
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Old 09-28-20, 04:48 AM
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If you can pump air out of the pump when it's not connected to the valve, then it's not the pump. Those dunlop valves were terrible for getting stuck, either the rubber tube sticks to the stem of the valve, or in the ones pictured above the little ball inside gets stuck to the valve seat. For a stuck rubber tube give it a wiggle or replace it. A bit of spit helps with that. With the ball type you can try giving it a sharp blast with the pump while sucking on the other end.
They are easy enough to replace, remove lock nut, wiggle valve till it comes out of the valve stem.
Yep, when car valves turned up, it was luxury. Before that we used to scavenge tubeless car valve stems, you could jam it over the valve and then jam the air hose on the other end, hold it tight and get some air into the tyres.
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Old 09-28-20, 08:51 AM
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Originally Posted by Winfried View Post
Out of curiosity, how do you change an old valve?
Originally Posted by Trevtassie View Post
They are easy enough to replace, remove lock nut, wiggle valve till it comes out of the valve stem.
As Trevtassie says, you unscrew the holding collar and pull the core out. When the rubber hose is in, it may fill the space between the core and the vent, making the core difficult to pull out, hence the wiggling. The hose rubber is not fully cured, so it is actually easy to rip it when pulling . At times, the hose is longer than needed and you can salvage a piece of the hose in a pinch and restore the valve to some operation.

The rubber in the Presta and Schrader valve washers is harder and lasts longer, but if you wait long enough, you may run into a time window where the tube is still good, but the washer went bad. You can still salvage the Schrader then, but Presta only if the core happens to be removable.
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Old 09-28-20, 09:31 AM
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Originally Posted by Winfried View Post
Out of curiosity, how do you change an old valve?
The easiest way it to change the tube it is attached to. Get a presta valve tube for US$4 and don't look back.

The best thing about hitting yourself in the head with a hammer is how good it feels when you stop.
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Old 09-28-20, 11:13 AM
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Newer Dunlop valves don‘t use the rubber hose anymore.
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Old 09-29-20, 02:21 AM
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Thankfully, we could get new tubes (with Schrader valves) at a nearby supermarket. Otherwise, we were stuck in a small town.

By "rubber hose", you mean this part?

Why do Dutch/German bicycle brands stick to Dunlop valves? I read they can withstand higher pressures than Schrader/Presta, but is it true?
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Old 09-29-20, 08:13 AM
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Originally Posted by Winfried View Post
Thankfully, we could get new tubes (with Schrader valves) at a nearby supermarket. Otherwise, we were stuck in a small town.

By "rubber hose", you mean this part?

Why do Dutch/German bicycle brands stick to Dunlop valves? I read they can withstand higher pressures than Schrader/Presta, but is it true?

Nah, the original version of the dunlop valve had a simple spike with two holes, that a little rubber tube slipped over. The tube acted as a one way valve, blocking the holes and also sealed the valve against the stem. The one in your imagine is the "modern" version of the original,, there is a little rubber ball inside the tube with a spring to hold it against a seat. When we were kids we'd swap out the old rubber tube ones and replace them with these ones, cause the tube ones sucked.
I reckon they've kept using Dunlop valves because they know their customer doesn't want to buy a new pump to suit schrader and doesn't want to fiddle with presta. Both of which can handle way more pressure than any utility bike would ever need. Even schrader valves cope with 100PSI pressure when used on trucks.

Last edited by Trevtassie; 09-29-20 at 08:19 AM.
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Old 09-29-20, 08:20 AM
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Originally Posted by Winfried View Post
By "rubber hose", you mean this part?

Why do Dutch/German bicycle brands stick to Dunlop valves? I read they can withstand higher pressures than Schrader/Presta, but is it true?
No, you show a picture of a new improved valve that does not use the hose anymore. The traditional one, with a hose, is shown below. Otherwise utilitarian bikes tend to uphold local traditions and stick to the solutions that local customers are used to, I carry a Dunlop hose in my tube repair kit, because I may get a local bike somewhere on loan and may run into a problem such as yours and want to be able to fix it on the spot. I do not want to change my kit depending where I am going and to figure out what kind of valves they use there. That hose weighs nothing.

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