dglevy

jimc101

Why not resolve the root cause of the issue, not try and and something else to fix? de-bur/file/sand the area smooth?

Litespud

Assuming it an aluminum or carbon rim, a rolled up piece of 120-220 grit sandpaper should be sufficient to round off the edges of the valve hole. Also, maybe a piece of rim tape over the hole (or completely replace the old rim tape), cut an "X" across the tape covering the hole and push the four sectors down into the hole, so that the tape covers the edges. Also, ensure that your valve stem is in straight and not at an angle when the tire is inflated. If not completely perpendicular to the rim, deflate and shuffle the tire around the rim until the valve is straight. Also ensure that you're not torquing on the valve stem when inflating - not an issue with a floor pump, but can be a problem if using a frame pump.

Andrew R Stewart 

How close to the valve's actual shaft base is the tube's failure How far from that same point is the edge of the rim's valve hole? Do these exactly line up with each other?

Reason I ask is that I see very few tube failures that are right up against the valve shaft that are also not from the tube stretching (the two biggies are too small a tube width or too little air pressure). After you fix a few thousand flats you begin to see that just about every rim has a sharp valve hole edge yet the number of flats due to it are quite rare. I've deburred many rim valve holes and seen flats close to the valve, on the tube, no longer being able to be claimed from a sharp hole edge. Andy

I should add that if one is wagging the valve back and forth (as in when using a frame pump) or are tugging on the valve (as in when removing a stuck air chuck) the tube can tear at it's base. But again the rubber is being stressed in a way it isn't designed to be.

fietsbob

Rim strip? did you take the effort to smooth the sharp edges ?

find an O ring the right size?

TimothyH

Overtightening the jam nut can pull the tube up through the valve hole causing it to fail.

Many just throw the nut away. It isn't really needed.


-Tim-

cannonride15

@dglevy, you can call it a product if you like (or market it!). I always cut a small piece of inner tube, punch a small hole in it and slip it over the presta valve before insertion into valve hole. Presto, no valve base problems with the sacrificial gasket in place! Guess you could (also?) deburr the valve hole, but I never have. Don't screw the retainer nut too tight!

Wilfred Laurier

Failures where the tube meets the valve hole are most often caused by rough handling when pumping. Using a mini-pump or frame-fit pump as your main pump will make it much more likely to happen.

I also had a cheap floor pump that was super tight on presta valves and I had a rash of damaged tubes until I returned the pump and got a slightly better one.

Hoopdriver

Great idea. I'll try it the next time, although I have never had the sort of problem that the OP described.

Retro Grouch 

Since you are having repeated failures and can't identify a physical cause, rule this one out first.

dglevy

Thanks to everyone who responded. All the posts have been remarkably helpful!

I am homing in on these two posts because they have made me wonder whether my impressions have been accurate.
Yes. Good point, Tim. I realized a few (several?) years ago that tightening the lock nut might be making trouble. So, I started just loosely tightening it. But you may have a good point. The failures that I mentioned may indeed include a time when I was over-tightening it. And, yeah, I noticed that Michelin tubes have smooth valve barrels--no lock nut at all. So, I may just start leaving the lock nut totally loose. (The lock nut is good to have at hand, though, only when I need to press hard against the valve, on the road, when I have to use a CO2 cartridge to fill the tire.)
Andy, yes, that's the problem I'm trying to address. I have a Blackburn floor pump. The chuck is pretty hard to remove, requiring a fair amount of force. I fear that it might be placing excessive stress on the tube, and this is happening 4 or 5 times a week. On the other hand, you say you have rarely encountered a problem at the valve base. Have you really fixed "a few thousand flats"? Are you a professional mechanic?
--David

Andrew R Stewart 

David- Yes. Today at work I worked up a $3500+ whole sale order, of largely service department parts, for the coming spring (as example of my duties). I have placed hands on many hundreds of service jobs (as reflected in service tickets) each year for decades, these days I do a lot less as I am transitioning to being retired. Since flat tires are the #1 service in a shop I think it's a fair estimate that I've fixed at least a few thousands of flats over the 45+ years.

To your issue- I'll bet you run Schrader valves. The pump hose chuck generally has a harder time releasing from Schraders then from Presta valves. But the very first step to reduce the difficulty is to lube the chuck before placing it on the valve. Spit into the chuck. Thick dribbling saliva is best. It will lube the rubber gasket and quickly dry out. And we humans have a nearly endless supply of this at no cost. When you release the chuck if at all possible hold the valve shaft below the chuck to support the valve. One reason that SVs are so lousy to use a hand pump with is that as long as the chuck's pin is pushing in the valve's pin you can loose air. So some air loss during removal is common, as is over inflating by a few Lbs to compensate for that loss. With PVs the big issue with chuck removal is to not cock the chuck, and therefore contact the PV's pin and loose air. Andy

Are you finding that your tires loose enough air every other day ("this happens 4 or 5 times a week")? What pressure are you aiming for and what kind of tubes are you using? The common weight (.9mm wall) tubes should hold enough pressure for a few days so unless you are riding over extremely bad surfaces and/or are using tires too narrow in width (actually in height) you shouldn't be needing to reinflate every other day. I run 700x25 or 28 tires on my commuter and don't need to top off the pressure for about a week, usually. And Rochester isn't known for it's road maintenance or smooth road surfaces. Andy

dglevy

These are presta tubes on a racing bike. 23c in front, 25c in rear. 105 psi in front and 90 in rear.

Thanks for your reply. You are making me think I might have mixed together period 1) valve base failure when I was over-tightening the lock nut and period 2) other problems at or near the valve base after i stopped over-tightening the lock nut. I may not have had so many problems during period 2. I don't remember. So, at this point, I'm inclined to stop worrying every time I yank the floor pump chuck off the valve. It may simply be NOT a problem, after all...

Andrew R Stewart 

The only times I install a valve base nut is on customer bikes since they generally believe the nut needs to be there. I never use them on my personal bikes. Andy

Lemond1985

I have had a couple sets of rims where if you didn't run the locknut to tighten the stem down, the stem made a buzzing sound because the hole in the rim was too large and it vibrated around while on certain roads. But otherwise though, I toss 'em whenever i can, just like the equally worthless plastic stem caps.

dglevy

I'm posting here b/c I thought it might be useful for others to have all the information in one thread.

I had yet another valve seat failure. I had tried a new setup--no retainer nut--but obviously that didn't work either. plus, it was unnerving watching the valve stem wiggle around as i put the chuck on it, so good riddance.

For the replacement, I followed the advice here above--a piece of old tube as a cushion, remembering to not overtighten the retainer nut. We'll see how it goes. I'm confident this will solve the problem, after, say, 4 or 5 failed valve seats. Thanks to all who contributed their ideas on this!

ThermionicScott 

Sounds like you need to get in the habit of holding onto the valve with one hand while using the other to flip the lever and pull off the chuck.

That way, you can limit the amount of wiggling or pulling force that gets transmitted to the valve base.

tFUnK

I've seen this a few times over the years. Usually it's the valve stem pulling away from the tube where the bond fails. Doesn't seem like it's a physical issue apart from just the age of the tube, so not sure it's entirely preventable.

DaveSSS 

I use michelin tubes with no threads. Easier to get the pump on and off.

jadocs

Twist the chuck back and forth while gently pulling up. Don't just yank on it like a gorilla.