Valve extender question…I ride a tri-spoke on front and disc on the back. Since the disc requires a short stem and the tri-spoke a long stem, I decided to go with one stem length (short) and use a valve extender (like the one above) for the tri-spoke.
Here are my questions:
Do I need to use teflon tape around the threads before putting the extender on the stem?
Is hand tight sufficient or should I “crank” it on?
Do you leave the valve “open” after airing it up? If so, is there the possibility of air leaking out?
Do I need to use teflon tape around the threads before putting the extender on the stem?
Is hand tight sufficient or should I “crank” it on?
Do you leave the valve “open” after airing it up? If so, is there the possibility of air leaking out?
Any issues with using a co2 gun on the extender?
Anything else I need to know?
Yes
Yes, but only if you use teflon tape.
Yes and no it will not leak air out.
No
There are other types of valve extenders like Vittoria’s that are self sealing. You remove the core valve, put in the extender and put the core valve in the extender. I prefer these over the extender you have. They do not require teflon, although you would have to remove/add the core valve depending on which tire you were replacing.
Follow-up question for you. I use the Zipp valve extender on my 404s. It is just a hollow tube, so, the value on the tube has to be left open. A short time ago, someone posted that you have to do something “different” when inflating the tires using a pump with a pressure gauge b/c the gauge will not give you a “true” reading of the pressure in the tube (obviously b/c the pump in not actually holding open the tube, b/c of the extender it does not touch the pin on the tube).
What does that mean? Do you go over or under the desired pressure when using a valve extender? How much?
What typcially happens on a poor valve extender seal or pump seal is that on the end of you downstroke you will get a accurate reading, but as you mentioned since it’s just a hollow tube and if it leaks your going to lose air pressure or show it slight inaccurately when the valve closes so you have to watch your guage really close and note it’s high point on the downstroke, this would be the true air pressure since the valve is open during the downstroke. This is why is prefer the Vittoria valves where the valve core is directly attached to the pump. I will use the hollow version for my spare in a race since with CO2 your not really going to know the air pressure anyways. Although with the hollow, I do still use teflon tape and just keep the valve extender had tight. I tape a tufo valve tool along with a razor blade to the inside of my seat just in case.
For the most part though, if your extender is sealed well, the variation in air pressure is going to be nominal and not really worth worrying about.
Great! Thanks for the info! I have the Zipp hollow extenders on my spare, but, I think I will follow your method and get the Vittoria extenders for the tubes on the 404s. I always use the plumbers tape to get a good seal, but get a little nervous about the tire pressure with the hollow Zipp extenders.
In addition to what j3kyl said, sometimes it is difficult to “break the seal”, in otherwords when you start pumping you are simply building up pressure in the extender, not in the tire/tube itself. This is why you tap the little end of the presta valve before you put the pump on it if you are not using an extender, or if you are using one of the Vittoria type extenders.
I have found that when using the Zipp extender with teflon tape I get an accurate pressure reading, at least as accurate as the pump guage is under normal conditions…none of them are perfect. Without teflon tape, i get some leakage unless I use an allen wrench to crank it down.
I prefer the teflon tape method, because if you have to pull your extender off to put it on the replacement tube/tire, it is easy to get off, and you can get enough of a seal on the new tube/tire to make it work. I also pretape the valves of my replacement tires, if it ends up going on my disc, the teflon doesn’t hurt anything. If the teflon is falling off because it has been on there too long, doesn’t really matter, just tighten it as much as you can and hit it with the CO2. Also, make sure your CO2 will fit in the disc hole, or that you have your crack pipe with you.
