[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. https://cimg6.ibsrv.net/gimg/bikefor...b0ec82f05f.png |
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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I've only ever seen one in the UK. No wonder the British lost the war of 1812. |
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. |
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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Originally Posted by Andrew R Stewart
(Post 21716709)
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 had no idea what it was until i saw a post about it on these forums. |
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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Originally Posted by 2_i
(Post 21716627)
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.
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://cimg2.ibsrv.net/gimg/bikefor...f4d5d2a353.png https://www.hema.com/en-gb/hobby-lei...-41198070.html |
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. |
Originally Posted by Winfried
(Post 21716924)
Out of curiosity, how do you change an old valve?
Originally Posted by Trevtassie
(Post 21716991)
They are easy enough to replace, remove lock nut, wiggle valve till it comes out of the valve stem.
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. |
Originally Posted by Winfried
(Post 21716924)
Out of curiosity, how do you change an old valve?
The best thing about hitting yourself in the head with a hammer is how good it feels when you stop. |
Newer Dunlop valves don‘t use the rubber hose anymore.
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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? https://cimg6.ibsrv.net/gimg/bikefor...1ff52af9ad.png |
Originally Posted by Winfried
(Post 21718770)
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? https://cimg6.ibsrv.net/gimg/bikefor...1ff52af9ad.png 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. |
Originally Posted by Winfried
(Post 21718770)
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? https://cimg6.ibsrv.net/gimg/bikefor...9d5d1a59c6.png |
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