nblack

I have a Trek mountain bike with puncture-resistant Kevlar tyres. These have done what they are supposed to for a long time but suddenly I am getting repeated flats (almost daily for a few days, using different inner tubes) with little obvious evidence of clear punctures.

Obviously, it might be bad luck but if anyone has any ideas, I would be very grateful.

Thanks

thehammerdog

also take off tires and turn inside out and make sure nothing is in tire itself. If you find nothing then well maybe you ar cursed by the Tire/Tube gods.

Torque1st

thehammerdog is on the right track, you have a sharp object embedded in the tire. Mark the tube and tire position. Pull the punctured tube and test it under water or with some liquid. Find the leak and note the location. Check the tire at the same location for debris. I always use this method for fixing a flat rather than just replacing the tube. Don't drag your fingers around the inside of the tire or you may end up with a punctured hand...

See thread:
https://www.bikeforums.net/bicycle-mechanics/326045-spare-tube-just-patch-kit.html

ericthered

Check the rim strip tape if you have not. I had a problem with mine that was making only tiny little puncturers that I did not find until I really over i nflated the tube and it stretched it apart. Miraculously several little slits lining up witht he spoke holes appeared. Some were not leaking but I figured that was my source. The rim tape looked okay but I still replaced it.
Eric

neil0502

Also, if you haven't done this already, take a small round file and "clean up" the edge of the hole through which the valve stem protrudes. I think the other posters have the right idea about your /actual/ issue, but ... it's not a bad habit.

The other thing CAN be a bad batch of tubes that get tiny tears AROUND the valve from "bad" or "aggressive" pumping technique.

It starts with finding the leak on the tube, though.

operator

Next time you pull the tube, inspect for where the hole is. This tells you quite a lot.

This is down to using ****ty pumps without flexible hoses. Mainly minipumps. Or that the rim valve needs to be deburred.

gosmsgo

I am as careful as can be and ripped 5 or 6 tubes this year. In fact I started oiling the valve and it still happened. I have finally put a nut on the inside and outside of my wheel to hold the valve in place rock solid. That has worked pretty well.

Yesterday i ordered the schwalbe Marathon Plus HS 348 so I am looking forward to 15,000 flat free miles!!!!

neil0502

Okay, so ... I don't get it.

If you were "as careful as can be," then ... how were you ripping tubes at such an alarming rate??

If the nut configuration fixed the problem, then did you have burrs in the valve stem hole, a bad batch of tubes, or were you using a mini-pump .... or what?

I'm not careful at all, and have never had this happen.

I'm sincerely interested in what you think the problem was that the nut thing fixed.

gosmsgo

I think the tubes I was buying were just crappy. I have no idea why it was happening.

neil0502

gosmsgo: I'm guessing you're exactly right.

In a moment of weakness, years ago, I recommended a buddy get the Performance tubes, on sale. He had no end of trouble with the valve stem base. Fairly sure they were glued on with snot* -- nothing else.

*Not that there isn't a place in the cycling world for snot, but ... in this case, it didn't work.

Al1943

Analyze. Where on the tube does the hole occur? That's the first step.
Keep the tires aired up.

Al

nblack

Thanks, all.