Flats From Valve Stem
 

I seem to get flats from the base of the valve stem, basically, where the valve stem meets the tube, and I'm wondering if that's just basic wear or what.
Also, should I be tightening the ring nut on the valve stem onto the rim pretty hard, or leave a little play?
These are 700 X 23 and I usually go pretty high-pressure, around 120.
I live in Florida, so wondering if the heat is an issue. Bike is garage kept, no A/C, so it might just be time, wear, etc.
Hope you can help with suggestions.
Thanks!

S

Quite often this is caused by either a sharp edge on the rim around the hole or by being rough on the stem while inflating. And I never use the lock rings.

My understanding is that the lock ring's sole purpose is to assist with inflating, keeping the valve stem from getting pushed in when the pump is attached.

As for the tube, I got a special price on three Nashbar tubes a couple of years ago. Each one failed at the valve stem to tube interface. I don't know if it was a design flaw (how can you screw up a tube?) or poor quality control on that batch.

I guess I can see how, if you tighten the valve ring too much, it would put stress on the valve stem.
Hey, they're cheap and mass-produced, whadya' gonna' do?

S

Probably as mentioned, rough metal around the valve stem opening. I like to use a countersink in a chuck and turn it by hand to deburr those edges. You`ve probably bot a double walled rim and the depressions in the rim tape over the spoke holes are a small indication of the amount of pressure that 120PSI puts on things.

I`m also assuming you have Presta valves and that the rims aren`t drilled out for Schrader valves. Otherwise a plastic sleeve/adapter is a good idea at those pressures.

If you actually have Schrader valves because thats what your rims are drilled for - suggest you try some Schwalbe tubes. Not all Schrader tubes are built to take that kind of pressure.

They're Presta valves.
Road bike, 700 X 23.
Thanks for all the responses, so far.

S

If your rim sized for Schreader valves by any chance? If so then it'll tend to make the Presta base dig into any sharpness on the stem hole.

If not then I'd look at demounting the tube and tire and lightly chamfer the stem hole. Beyond that I can only suspect that you're twisting and bending the stem excessively when putting on the pump. Or if you are using a frame pump for general pumping then you're not properley supporting the end of the pump to avoid excessive flexing of the stem.

Happens. Usually from just pulling the pump off a zillion times. Eventually the stem/tube join gives out. Some brands of tubes/runs of tubes are worse than others. Some pumps grip tighter than others. You don't need the nut at all. I only use them occasionally with aero rims when the valve stem clicks on the rim. The nut is probably most of your problem. I've had friends rip out my valves "helping" me to get my tires pumped with a hand pump on the road. Great care there, or use a hand pump with a hose.

I had a floor pump once that had an air jack that was unusually hard to pull off of the valve after use. It caused several tubes to be damaged in the way you describe and one schrader valve actually pulled right off.

I'm pretty careful with the pump, but I'm going to try and
ditch the valve stem nut.
Thanks for all the tips.

S

ride the tire below pressure, and the tire creeps on the rim
brings the tube with it, and shears off the stem, as it cannot also move, being fixed in a hole.

Ditto S'prince about checking for rough metal around valve stem hole. And I just finger tight my lock rings. Is the rim a double wall or single wall and does it have reinforcing eyelets? Some single wall rims w/o eyelets have the issue of a narrow channel for the spoke nipples. If too narrow, it can cause excessive deformation of the base of the valve stem and it may delaminate over time. Some double wall rims without eyelets will drill the hole through two layers of metal rim. In both cases, making sure a good fitting rim strip that is aligned around the stem hole will help cushion and protect the tube.

I'm having similar problems, these are my punctures, user error or bad tubes?

http://bikeforums.net/attachment.php...hmentid=208569http://bikeforums.net/attachment.php...hmentid=208568

Looks like tube getting caught between rim and tire bead near the valve, or you have a deep center channel in your rims near the valve hole this is unsupported by the rim strip you're using.

I had the same problem years ago, until I loosened the ring . No problem since then. I keep the ring in place for inflation, but it is very loose.

Several months back I had the front tube on my Hardrock blow out through the side of the Schrader Valve. It was loud as ****, I was sitting in my living room watching TV when the bloody thing blew. So far knock on wood I haven't had my presta valves blow.

As for the locking nut, none of my friends at the LBS that I go use them or the "Frisbee's" on the rear wheel. And in talking with them they agreed with me that using the locking nut is really only good for keeping the valve stem from "falling" into the tire.