Presta valves 101

[rpm]

I've pumped a zillion tires, but I still don't understand why this happens:

1. I open the valve and push it down to make sure it isn't sticking.

2. I attach my floor pump and try to pump and the handle won't go down and no air goes in.

3. I remove the pump head, move the valve up and down some more and try again and the same thing happens.

Why does this happen, and what do you do about it? (And why does it only happen when I'm in a hurry?)

[Lifelover]

PSI -

The pressure in your pump has to overcome the pressure in the tire before the presta valve opens. Same is true when you push it with your thimb/finger but when you try to apply the pressure via the pump have to apply the same pressure over a larger area. Thus. it's more work. If you did it wiht only 30 PSI in the tire it woudl not be as noticable.


Maybe not exactly right but hopefully you get the general idea.

[gemship]

I find it easier to get tires up to proper inflation by letting almost all the air out then attach the valve and pump :beer:

[L84dinr]

Mine does this, the hose causes the pump head to "lean" out of line with the wheel and i think the pump head is tilting the presta valve enough to close it, shrug. i have started placing the valve at the nine oclock (front) or 3 oclock (rear) position and have the pump head/hose kinda lean against a spoke to try to keep the pump head square and not "tilt" on the presta valve. Hope this makes sense.

I sure like my old silca pump with the press on pump head. Been rebuilt a couple of times and have tired of cutting up old belts for use as a leather washer. Hasn't worked well for quite awhile, bummer.

[gomez308]

I guess everybody has a little tip. After I give the first little pump, I grab the pump head and tilt it a little. I can hear the valve letting go and then it pumps up fine.

[alancw3]

i think it is a pump problem. if the pump head does not make proper contact to the stem then basically you are pumping to a blocked valve. that is why i love the presta only valve on my rennkommpressor. v similiar to the silca valve.

[rpm]

My thought was that it was a pump problem, too, with the thumb-lever style head tilting the valve. So I got a new Lezyne pump with a screw-on head, and that's the one that didn't work this morning. The pump had worked great so far, and I thought I had my problem solved, but evidently not.

Since it doesn't happen all the time and with different tires, I wonder if it's a valve problem, like the valve head gets bent a bit.

[uno-speedo]

Mine does the same. I usually wiggle the pump head very slightly whilst its attached to the tube and I'll hear a faint pop noise and then I'm good to go.

[Kevan]

I can go to sleep tonight knowing I'm not the only one experiencing this.

One mystery solved, three to go.

[fiamme red]

And why does it only happen when I'm in a hurry?It's one of the corollaries to Murphy's Law: "If there is a worse time for something to go wrong, it will happen then." ;)

[palincss]

It's not the pump, it's the valve. One of my valves does it, the rest don't. I give them all a gentle tap before pumpuing, but on the sticky one a gentle tap doesn't do it, I have to deliberately push the valve stem in and bleed air out. I generally bleed that one down to around 30-40 or so.

[Chief]

The problem is with the valve and not the pump. Try slapping the side of head pump while under pressure from the pump to loosen the stuck valve. The extension rod of the valve may also be bent and is causing it to hang up when you push on the pump head.