Flats at the valve stem
 

I need help- I am having too many flats, and at home when I look at and re-inflate the tube, the valve/tube connection is the problem. I am careful to install the tube correctly (10 years bike shop experience and 30+ years of riding has tought me that) (I think) being sure the tire valve is coming out of the wheel at 90 degrees. I have checked the valve hole- no nicks or little burrs there- very smooth. I ride 3 bikes pretty consistently, and all three are part of the malady- TOO many flats at the valve stem? I use a Lyzne floor pump and inflate the tubes to 110/115 PSI as the tire recommends. Could use any ideas. Thanks

I had the same problem.
Now I cut a piece of old tube with a hole in the center and place it on the valve when installing the tube.
No more problems.

Super Idea.. ^..
Actions I've taken.. Be sure the tire does not reposition itself during the repair.. Sometimes, it seems to reposition itself off center with the value not straight.. Seems that might have been a problem.. 2. While on the road , I've switched to mini-Topeak Pump with hose attached. Those single barrel pumps seems to vibrate the stem about while adding pressure , likely causing friction at the base of the stem. That seems to have helped.

are they new wheels or tubes?
if the first, then it can be some particularly sharp edges at the valve.
if the latter, then it could be a bad batch.

I usually use a fine tooth rattail file on at the valve hole to deburr it.
that or the rubber grommet from old tubes works too.

Riding under inflated would also do it, tire creeps around rim,
and takes the tube with it.

Tube moves , but hole in the rim, obviously doesnt move.

I put the valve nut on the inside of the rim. The stress of pulling off the pump no longer is on the rubber.

I've done the same thing and it does work well to protect the base of the stem.

BTW, are all the flats with the same make and model of inner tube and were they bought at the same time? You could have a bad batch of tubes.

I had a bad batch of tubes give me heck a couple of months back. They were Giant thick-wall tubes, and each one failed at the stem. Fortunately, the LBS exchanged the tubes without issue, as even a couple of tubes that I had them install did it. I got tired of the tube issues, and switched to some light weight tubes and haven't had any stem leaks since.

Thanks to all for their thoughts and ideas. I think I will do two things 1) put a small piece of rubber by the tube stem when I install a tube 2) Not leave the tire mounted on the rim till I get a flat. Meaning, after a month of riding (as the spirit moves me) I will remove the tire/tube, clean the rim, tire,tube-retalc the tube- and re-mount the tire tube on the rim. Again- thanks to all Bob

I think this is a mistake. Removing and replacing the tire and tube frequently is much more likely to damage both. Just install them one time properly and leaving them alone until you have to change them for cause. Most flats are the result of a puncture in the tire/tube, not from failure at the valve stem and if that persists, you have to locate and fix the problem.