Presta Adaptor Doesn't Seem To Work
 

I shifted from Schrader to Presta tubes recently. My LBS sold me a Presta valve adaptor so that I could pump the tire even from a Shrader-only pump. The guy at the LBS even demonstrated to me how the adaptor is put on the Presta valve and how to pump the tube with it.

Upon trying it at home, I find that the adaptor doesn't quite fit the situation. I unscrew the small lock of the Presta valve and make it reach the tip of the valve. I then burp the tube and apply the Presta adaptor. However, I find that my Schrader pump cannot pump air into my Presta adaptor. It appears that the tip of the Presta valve (the one that releases the air when pressed) is not long enough and does not protrude into the adaptor and therefore, air cannot pass through the valve. I can't even release air with the use of my fingernail. The same thing goes with my Schrader tire pressure gauge. It's frustrating because I saw it done correctly with the very same adaptor in the LBS. Looks like the Presta tip isn't protruding long enough out of the adaptor. What am I doing wrong?

FYI, I have no problems using the Presta valve with a Presta pump. But that isn't really the point. I sort of wanted the confidence of having a functional adaptor with me when I ride. What's more, my tire pressure gauge is Schrader, and I prefer pumping my tires to the correct pressure everytime I ride. As it is now, I have no idea what my pressures are in my tires.

I'd appreciate all you input.

Before you screw the adaptor on, tap the unscrewed valve on the tube few times releasing some air . This should help :)

The Presta core isn't supposed to contact the Schraeder nib in the pump head. Until about 25 years ago, most of the Presta adaptors on offer were about twice as long as the adaptors sold these days; I assume the long adaptors were made that way precisely to avoid the possibility of the Presta core contacting the Schraeder nib. The short adaptors crowded the long ones out of the market, probably because people familiar with the way Schrader valves work thought that Presta valves work the same way and that a long adaptor couldn't work as well as a short one.

Presta valves have some advantages over Schraeder valves, but one disadvantage is that they can be mysteriously cantankerous about opening to admit air. For some tubes the valves work perfectly all the time; for others (including yours, I'd guess), you need to let almost all of the air out before the valve admits that resistance is futile. Again, a floor pump gauge is rock steady with some Presta valves; with others, the pressure indicator keeps plummeting like the altimeter in a dive bomber. Enjoy.

have you tried screwing it all the way on, you know so it goes past the rubber seal inside the adaptor? If you're just screwing it on till it's kinda snug, you're probble not getting past the rubber seal.

With that being said, dont rip your valve stem off.

I'll try that.

Also try releasing some air from the tyre with the Presta nib fully extended BEFORE you attach the Schraeder adapter. I had the exact same problem the other day. This relieves pressure inside the tyre making it easier for air to circulate. Found it made all the difference. Also make sure you screw the Schraeder adapter all the way down to the Presta valve and check that the connection of the adapter to the pump hose is as tight as possible. The nib of the Presta valve after you attach the adapter doesn't need to make contact with the tip of the pump hose. Good luck!

My take on this is the pump is the culprit. Insufficient pressure to 'open' the valve.

The way I understand this is that I must overcome the pressure to open the valve should I want to pump in air. If that is the case, then there's no way I can use a handy digital tire pressure gauge with the adaptor? And why is it that I can use the same pump, switched to its Presta head, on the Presta valve without any difficulty?

I don't think the pump is necessarily the problem as I used both a floor pump and an air compressor without any success until I released some air pressure from the tyre before attaching the Schraeder adapter. Finally the air compressor won out but not before adjusting the position of the adapter on the Presta valve and checking the connections.

The problem is that there is much more surface area on the inner side of the valve than there is on the outer side. Therefore, any pressure present inside the tube must be overcome with a far greater pressure to cause the valve to open. It is not uncommon to have to partially deflate a tire for my shop compressor to inflate them, or alternatively sometimes I just reach for the floor pump cause I can easily push in up to 160 psi and that will usually open the valve if the tire was slack enough to be needing some air.
Dan Burkhart
www.boomerbicycle.ca

If your adaptor fits to tightly or if the presta stem is slightly bent, you may be screwing the stem back into place when you put the adaptor back on. I've had this happen in the past. I don't use the adaptors at all, although I do carry one (I think) in my on-bike tool kit.

If you want to use a schrader pump on a presta, especially a floor pump, you could use an adaptor like this.

bingo
The little pin gets stuck and you can't get it to release w/ pressure. Jerk it around a bit to help that.

Also, don't be shy with the pump. It will never push air in with the first stroke if the tube is semi-pumped already when you go at it. You have to build up pressure in the pump's nozzle tube to make it move the valve. On my floor pump w/ a long rubber tube that easily takes 5-6 strokes.

Doesn't sound like what's going on for you, but one problem I've had with these adapters is the loss of the rubber seal. Took me a while to figure out why there was so much air leaking around the adapter. One of many "duh" moments.

A less fiddley fix is to change the air pump hose for one with a self adapting valve attachment. The one my LBS sold me works great on both types of valves. Most new frame pumps self adjust also. I haven't used an adapter in several years. It is true that you may need several pump strokes to build up pressure in the hose before it overcomes the pressure in the tire through a presta valve. Unfortunately, with a schrader valve it is possible to let air out of the tube when using a low pressure air compressor on a high pressure tire. Most gas station compressors are set for car tires and may top out at 40 psi or so. Presta valves shouldn't allow this but I have used adapters that did. It's pretty annoying to pay 50-cents to give the station your air.

Im curious as to why you switched, assuming these arent different wheels drilled for presta.

I thought I'd try out the Presta valves, considering all the good reviews I heard about them. Actually, they are indeed easier to pump with a Presta-headed pump. I just want to be able to use my adaptor with a Schrader pump. You'll never know when you may encounter such a situation where there's no Presta pump.

Pumping update: I went back to the drawing board to try again. This time, I heeded your advice and deflated the tire first. I put on my adaptor and clipped on the Schrader head of my pump. Lo and behold! No problem whatsoever in pumping the tire!

Did give me some insight as to how differently the Presta valve works from the Schrader. I actually was thankful for this small problem because it did teach me a lesson in basic bicycle mechanics. Now, I am able to appreciate the principles behind both Presta and Schrader.

On the other hand, considering the fact that pumping into the Presta valve works on the principle of overcoming air pressure, does that mean that I may not be able to use my handy tire pressure gauge on the Presta-to-Schrader adaptor? Or, to paraphrase the question, without the use of a built-in pressure gauge on your pump, how do you measure tire pressure via a Presta valve?

You're right, you can't measure your pressure with your handy Schraeder gauge after pumping, and if you try you'd lose most of the pressure anyway. :cry:

You can use a Presta gauge (I don't bother) :)

Unfortunatley, now that you've got the adapter mastered, the adapter will be for emergency use getting you home after a leak/puncture. You'll have to squeeze the tire with your hand to get a ballpark idea of your pressure.

For serious rides, use the gauge on the pump.

You get a pressure gauge like this one. Works on both. The thumb tests, by the way, is highly inaccurate;)

You should just get a topeak road morph. It has a gauge. It is a minipump so you can take it with you on rides. It gets my tires with presta valves up to 120 psi. What's not to like?

I got this mini pump recently. It has a built in gauge, works for both types of valves and delivers a consistent amount of air per stroke regardless of what the initial pressure is. No pre-deflating needed and it doesn't take a superman to get past 80psi. Oh yeah, it's also one of the few things not made in China.
http://www.velo-orange.com/quickerpropump.html

What type of tube is it? Does it have threading all the way down the valve? I bought a set of Giant presta tubes that have the smooth valve and they don't work with my presta adapter. My fully threaded presta valves work fine though.

+1 - I bought 3 adapters until I succeeded pumping air. I noticed that first 2 had no rubber seal. Also noticed that bike shops sell adapters for Schrader to Dunlop - Dunlop thread seems to be the same as Presta. I believe the ones without seal are for Dunlop.

The Dunlop valve is very rare in the U.S. You will not find adapters commonly here though my recently bought floor pump came with a Dunlop adapter, presumably for international sales.