Patching Tubes at the valve stem
 

It could be due to my miserly choices at the LBS or it could be my wheel, but I have had several punctures right at the base of the valve stem.

I had written these off as cheap tubes, and moved on to a new one.

This time, I cleaned up some burrs on the valve stem hold and tried to smooth it up as much as possible - so we'll see how that goes.

My question is, (and I searched unsuccessfully for it already) "is it possible to patch a puncture at the very base of the valve stem?"

thanks in advance :)

i've tried, but it didn't work

I've never had punctures in that area. It must be from the wheel rim. It can't be from road hazard damage. Make sure the hole through the rim for the tube valve is smooth.

I'd be dubious about being able to patch it. Even the smallest patches have room for about 3/8 of an inch of rubber all around the puncture. The valve stem might not leave you that much room, and the hole would be close to the edge of the patch. It wouldn't have a good chance to hang on.

So have I and it didn't work for me either. The tube is toast. To prevent this in the future, cut small rectangles out of the defunct tube, say 1" long by 5/8" wide, and punch a hole the diameter of your valve stem in the center. Slip this patch over the valve stem of the new tube before you install it. This provides a second layer of rubber at the valve to protect its base.

The rim could be the source of your problems, but another possible source for holes in that area is force applied to the valve stem from a pump. Hand pumps can be prone to pulling the valve stem side-to-side if you're not careful and have been known to rip a valve stem out. I've had a floor pump with a really tight chuck that ripped out a valve stem when I tried to disconnect it. I've known of at least one person who puts a nut from a threaded presta valve on the inside of the rim so that any force on the valve stem pulls on the nut, not on the rubber tube. I suppose that might also possibly shield the tube from being pinched or punctured at the hole if that's your problem.

Here's a good idea right here^

I use Presta tubes, and my floor pump has a tight fit . ... I suspect this has something to do with it

because of a change in valve stem design and unreliable bonding of the tube to the valve, I've been reinforcing my tubes before packing them as spares. I use a feather-edge patch from Rema, or Earth, punch a hole dead center and bond it in place. A standard paper hole punch just happens to be the right size for my PV tubes.

The same system, would work for a leak near the valve.

BTW- if you also have valves separating, be aware that the patch idea works as a preventative, but does not work as a repair.

Well, I have certainly seen some valve repair patches for Schraeder, from supply providers for agriculture, for ~$2.50 apiece. I wonder whether one get a Presta edition and how well they work. In any case, see the Rema site for a start.

That's my bet too.

Yeah, I found that out to my misfortune on a trip last summer. Of course, it was a trip where I was stupid enough to not have a spare tube, assuming that a patch kit was sufficient, too. Luckily my riding partner had a tube that, while not the correct size, was similar enough to allow me to inflate my tire enough to ride the remaining 70km home, otherwise it would have been a VERY long walk.

I have had the problem I usually attribute it to crappy pumps stressing the stem against the rim. Nice tubes have a nut that holds the stem in place. Also make sure that the tube is the right size positioned correctly when inflated, as far as repair you could try copious amounts of super glue don't expect excellent results.

The cause of your flats, or of tube failures in general, can often be determined by a combination of the location and the appearance of the puncture/failure. Wondering if you remember the exact location and appearance of the failures at the valve. I can think of only three causes of failure right at the stem base:

• Pump misuse: I would think that tearing the valve base from pump misues would be apparent after a few incidents, but is possible. It would never be a clean cut, but rather a rough tear.
• Defective melding of the stem to the tube: Very rare, cheap tubes or not, usually obvious when they occur.
• Tube migration: If one uses valve stem nuts and the tires are not kept well inflated the tube can migrate sufficiently so that the rubber at the base of the valve is stretched until it finally fails. The failure typically is a crescent-shaped tear, ofent at the edge of a small "bubble" of stretched tube. The failure would be on the side of the valve toward the front of the bicycle. The failure typically takes quite a while to develop.

NOTE: I did not mention a rim problem because Unless the valve hole had a significant, sharp, downward facing burr it would cut into the side of the valve, not the base.
ALSO - I am not saying oine should not use the stem nuts - don't get that one started again!

Add to the above

Pinch flats caused by trapping the tube under an improperly seated tire bead.

Don't those usually announce themselves with a loud BANG when the tire is forced off the bead seat by the trapped section of tube? Pinch flats (aka snake bites) are usually the result of inadequate inflation pressure and/or hitting a hole or other hard object in the road.

Not always. It's possible for thin sections to be trapped without lifting the tire enough to blow it off. I see it more often with hook edge rims that don't have raised shoulder seats, like the old Mavic E rims. Sometimes as the tube is inflated it pulls itself free, but the damage is done.

I doubt the same installation error would occur "several" times, so I did not include that in this case. In general that is certainly a possibility any time one experiences a flat.

With all due respect, I disagree. I've found folks who do things wrong to be amazingly persistent. Apparently they've never heard Einstein's definition of insanity.

I had a tube that had a tiny tear at the base of the valve. This was years ago and the valve had a nut at the base. I removed the valve and patched the tube, then made a new hole away from the patch and refitted the valve. It worked fine, but as I say, this was years ago ( say 50...)

The cause could also be over-tightening the round stem nut.

Your rim tape might bear replacing. If it's hard plastic that might be your culprit too.

No way to effectively patch a flat in that spot.

BL