Presto Valve question
 

After pumping the tire and removing the pump I found my valve no longer visible, I guess it is jammed inside. How soon should I change it and anticipate that I will get an air leak from that? Is it safe to ride?

Thank you for the advice.


Olga

Not safe to ride like that. Deflate and start over. Won't deflate because the valve is inside? Buy a new tube and pirce the old one with an ice pick through the hole in the rim. An $8.00 tube now will save from from a long walk home.

Broken PV valve stems are about as common as 3 leaf clovers. (maybe not quite that common). It really doesn't natter because a PV is a simple check valve and the tire pressure alone is enough to keep it reliably closed. The only issue is that the OP will now need a pin of some kind to let air out if he wants to.

BTW- the little nut and stem extension aren't somehow jammed inside the valve. They're inside the pump head, or fell out after you removed the pump and dropped on the floor.

Yes, as long as the tire holds air, which it will 99% of the time, the tire is safe. The worst that can happen is that the tire loses air and goes flat, and flats, regrdless of cause are inconvenient, but not dangerous.

It's not safe to ride, and it "Presta" . . .

Rim holes can be drilled to the correct size to fit standard schrader valve stem tubes.

Just because you can, doesn't mean you should. And FB actually knows stuff. So the OP might should take his advice on this one.

Even if it holds pressure just fine, you won't be able to add any more air for your next ride. As soon as you blow in some air the check valve will come off inside the tube.

And presta tubes ARE the standard.

It's kind of funny, folks have been breaking the nut off and pumping their tubulars using Silca pumps daily and I don't know anyone who ever blew the stem into the tube. On the older valves made in Italy it wasn't at all possible because the hole in the base had a reduced diameter. But I know people with modern valves with broken stems where the stem could come out the bottom, but it doesn't. Possibly because they pump with the valve at 12:00 and gravity is working for them.

In any case, the OP's valve must still be in place since the tire is holding air. and the WORST case scenario is that she blows it into the tube, and has to replace the tube. Until then it will hold air, so the choice is whether to replace the tube now, to avoid having to replace it alter, or to wait until she has to replace it. As I see it, she has nothing to lose by waiting, and with any luck she can use this tube until it flats for another reason.

So the valves in tubulars are somehow different? I never noticed. It happened to me on a clincher on a century - got a flat, changed the tube, turned out my CO2 inflator wouldn't take my cart so some guy lent me his mini pump and I got it pumped up but when I took off the pump there was just nothing there... like a hollow cylinder. When I got to the rest stop I used the mechanic's pump and then the check valve fell out and the tube wouldn't hold air. So maybe it was something more than just breaking off the little nut, maybe my valve in the spare was flawed to begin with.

Yeah. My experience with presta tubes with broken off nuts is they work until I try to add air. Even with the stem at the top pointed down and trying to pump very slowly the poppet get blown irretrievably into the tube. Of course you might get away with it, or perhaps you have a stem that prevents the poppet from going into the tube, but in stems with non-removable cores the stem has clearance to insert the poppet from the inner end during manufacture.

If prestas are the standard, why are they not used on aircraft? Or Busses. or big trucks. or...or...or...

Check to see if your rims can be drilled, change to schraders.

None of those inflate to high pressures on narrow rims for one thing.

Presta valves have 2 advantages uniquely suited to bicycles.

1- the stem is narrower, so they allow for narrower rims. Note that this isn't a rim strength or room to drill issue. It's about the sum of widths of the valve and two tire thicknesses which determine the minimum inside width of the rim's tire flanges.

2- they're springless check valves, which makes them ideally suited for hand pumping, and eliminates the need for a valve depressor in the pump head, and/or air loss when the head is removed. This also simplifies the design and use of the pump heads since they need only provide a seal to the shoulder of the valve.

If either reason applies, Presta is a better choice, otherwise it's a toss up.

Yes. They are perfectly suited for deep V carbon wheels. Yay. Most of us are mortals.

And while they are not narrow wheeled vehicles: Tire Pressure On A 747 — Tech Ops Forum | Airliners.net

In other words, check with your lbs to see if your rims can handle it and "DRILL BABY DRILL ! "

*presta hayter 4 lyfe*

I don't think it's about tubulars, but the valve maker. Some things were lost in translation when the valve production moved from Italy to the orient. For example ole timers will confirm that BITD it wasn't necessary to "burp" valves before pumping. So there was a change either in the material of the O-ring or the shape of the valve seat (or both). Plus valve separation from the tube was virtually unheard of, and now it's fairly common.

IMO this is a natural consequence of placing the need to squeeze every last mil out of the cost vs. producing a product worth putting your name on. Tubulars were relatively expensive and no maker wanted to have his reputation suffer over bad valves. The same used to be true when folks like Michelin, Continental, and others made their own tires and tubes. These days bicycle tubes are completely generic with the source being the lowest bidder, which moves quality to the back burner.

They are pretty much the standard for bicycles -- the actual context of this discussion. What exactly would be gained by converting the rims to Schrader?

In the world of repairs out in the field, it pays to have the most common items available. OR carry everything you need all the time. At the very least, one of those presta adapters, which get lost easily.

Dear Olga:

You have heard from both camps on this. If you can find a situation that's better than either of these presented, take it.

Sincerely,
Rich

BTW- whatever plays out with this tube, if you're going to stay with PV, it pays to learn how not to break the nuts off.

Despite pumping thousands of times (maybe 10s of thousands) since, the last PV valve I snapped the nut off was back in 1968 or so.

It's easy to damage valves, including breaking Shrader valves when hand pumping. It's just as easy not to. The difference is in learning basic techniques for fitting pumps, and properly bracing then when hand pumping.

I don't understand the hate for Presta at all. I've only been using Presta on my bikes for the last few years, but there's no way I'd go back to Schrader. Presta just works better.

Of course it does. And any pump your purchase with which to make will, of course, deal with Presta just fine. And just in case of a severe emergency that requires pumping quarters into a gas station compressor (perhaps you broke your mini pump fighting off a bear, and expended your CO2 cartridges attempting to do whipits) can be dealt with by throwing a tiny adapter into your saddle bag.