Presta Oddity
 

Has anyone else had this experience? I found that I couldn't top up the pressure in high-pressure tires that are down only a few pounds unless I release a lot of air first.

Example: If a 130 psi tire is about 10-20 pounds low, I experience a "lock-out" condition with my Topeak Joe Blow floor pump until I release another 20 pounds or so. If I get the tire down to 80-90 psi, I can then add air. The lock-out means I can put my full weight on the pump handle, but nothing gets through the valve. The pump's gauge goes way up as if the tire valve core were screwed shut. Initially, I actually thought the core was frozen shut, but it's apparently just the amount of pressure still in the tire that keeps the valve from opening.

Once I learned that I needed to release pressure in order to add pressure, it wasn't a problem - just another step in the inflation process. (I'm sharing this earth-shattering discovery because I have nothing more profound to contemplate at the moment.)

I've experienced this same thing with my Topeak Joe Blow Sport. I think it has to do with the valve sticking a little bit and that stickiness will make it quite difficult for the pump to overcome as the pressures are already quite high. So I always release a little bit of pressure to make sure I don't over-pressurize the valve or something because that'd be just my luck! Sure it's rather inconvenient to a small degree, but I'm glad I'm not the only one who has experienced this before.

Yes.

Just "burp" the valve enough to release the smallest amount of air possible before attaching the pump head.

It is your pump's way of telling you that you need larger tires. Seriously.

But I love my skinny, minimalist tires! Seriously, I hear ya. I also need a Schraeder adapter screwed onto my Presta valves, so the process is fairly involved. The last time I tried to inflate without using the adapter, the valve core snapped off. Way too fragile a design, IMO.

Millions of people might disagree. Andy.

Don't get me wrong. My Schwalbe 700 x 23 tires are a pleasure to ride on. Worth the hassle, such as it is.

As noted by a few above, the key is to "burp" the PV before pumping. The seals in the valve are pressed into the seats by the high pressure inside, and after a few hours that way get stuck.

To lose the minimum air possible, I use the pump chuck and hose and bang it against the valve (after backing off the nut). The small Psst is testimony that the "burping" successful, then I attach and pump.

In 9 out of 10 cases the only issue is in the valve itself, and has nothing to do with the pump.

I've had certain tubes do that. I just burp the valve.

I have a Joe Blow pump as well and it works GREAT. Since I always burp the valve before attaching the chuck, I have never had a problem adding air.

-SP

Chiming in with the burp. When I first switched to presta, I had he same problem. I had no idea what was going on. People here told me burp it, and now I do. Just a quick poke with my fingertip after releasing the nut.

I have the same problem with my Joe Blow pump. The same tube doesn't give me the same problem with a Serfas pump I also have. On all my tubes I always give it the smallest little 'burp' before I pump, but on this tube I MUST let out enough air to get down to 80-90 or it WILL NOT pump up. The same pump on a REI tube on the front wheel never gives me the same issue. I keep thinking I can just change out that problem tube, but laziness seems to stop me. (I also do not want to anger the Tube Gods since this tube has given me no problems for many miles. If I make a non-essential change, I'm afraid I will face Karmic retribution.)

Interesting that two tubes would act differently. I have two bikes with high-pressure tubes (a mix of brands), and all require some deflation before filling.

In the interest of science, I'm tempted to push the pump dial beyond the pressure in the tire to see if that would open the valve. Theoretically, if the pump pressure exceeds the tire pressure, the valve should open. I won't try it, though, because something could break in the pump.

Don't. I broke an annoying Lezyne screw on pump by trying that. Happy to be rid of it.

Of course that's how it works. With every stroke, the valve remains closed until the hose pressure exceeds the tire pressure, pushing the valve inward and opening it. After ward then the hose pressure drops the valve closes until the next stroke.

The issue is that valve sticks initially so air alone won't open it unless the differential is super high (mine force open at about 200psi on a 90psi tire). The experiment won't hurt the pump, but repeatedly taking the gauge to the end of the scale can alter it's calibration. SOP in the pressure gauge world is not to routinely run gauges above 80% of the scale range, with staying below 66% being best.