Cycling - Way Too Many Flat Tires

[Ratsima]

The good news is: no flats for the past few weeks!

Thanks for the interesting thread on tire pressure. So many varied bits of advice.

Beautiful flower, by the way. Anyone know what it is?

[Puwa]

Hi, did you ever get to the bottom of the problem, or at least find a lasting solution?

[T_Dog]

Some more clues to the valve stem ripping problem. I decided to clean up some corrosion on the valve hole I had noticed a few days ago. Took the rim tape off (seven years old) and cleaned off the rim, scouring off the light corrosion and then sealing with epoxy. Put the old rim tape back on, re-installed the tube, and pumped it up. Ready to go.

Yesterday I went for a ride and got a flat. Ripped valve stem. Put in another tube and ten minutes later, same problem. I noticed that the rim tape had bunched up opposite the valve area. That new tube failed about 15 minutes later. After doing some research on the web due to a friend's suggestion, found many threads where the root cause was the tire rotating on the rim when you apply hard braking. When that happens, the tire pushes the tube and since the valve stem is in the rim and can not move, the tube fails there. (Just as if the valve stem was being bent over, but it is the whole tube moving.)

This is a common problem in motocross I guess and never suspected it could happen in our mountain bike set ups, but I am sure this is what was going on. I am going to buy some new rim tape that will have good sticky adhesive and I am sure my problem will go away. The old tape would just slide when I hit the brakes, allowing the tube to rotate with the tire, ripping the valve stem area.

[BBbUn]

Hey Ratsima,

I've been having a very similar problem with my bike lately. 700c x 45 mm tires, presta valves. I've got new rim strips, and even a bit of rubber to boot the valve stem. I tend to run lower pressures.

Been knocking a lot of valves off tubes...

Not read through the whole post, so forgive me if I'm repeating suggestions, but here are some tips I've been gathering in trying to improve my problem:

- don't tighten the valve nut at all. Just treat it like a support for pumping a flat tube.

- use a small square of tube around the valve to give that area an extra bit of protection

- run a moderate pressure. Too high and things pop in the quiet of the night. Too low and the valve takes a real beating from shifting inside the casing, especially over rough terrain. I've been advised, based on information off Jan Heine's blog (this guy is a serious long distance cyclist and bike researcher), that the ideal pressure allows 10% tire deformation against the road, under a rider's weight.

Good luck!

The tires are 26 X 1.90 and are rated at 35-65 psi. The tubes are 26 X1.90/2.125. I don't see any pressure rating on the tube.

Two days ago, after my previous photo post, I carefully installed a brand new inner tube. I was very careful about proper placement. I had tightened the nut, but loosened it before I got on the bike. I rode about 300 meters Friday evening when it started to rain, so I rode back. That's about 600 meters total. When I went to ride Saturday night the tire was flat. I've yet to remove it. I'm pretty bummed out about the whole mess.

I mean, I've been riding for years and years and have been installing inner tubes on a variety of bikes for a very long time. It's hard for me to believe that all of a sudden I have improperly installed a dozen inner tubes one right after the other. I'm not doing anything different from what I've been doing all my long (61 year) life.

It's uncanny.

[BBbUn]

Hey Tdog,

I ordered some Schwalbe Urethane rim tape that is supposed to be the bees knees. It is quite a padded, semi-sticky surface.

I'd get you one of these to try, but unlike cloth tape, they are pre-fit, and mine are all 700c x 22 size. Not tried them yet but can see why they might help!

Some more clues to the valve stem ripping problem. I decided to clean up some corrosion on the valve hole I had noticed a few days ago. Took the rim tape off (seven years old) and cleaned off the rim, scouring off the light corrosion and then sealing with epoxy. Put the old rim tape back on, re-installed the tube, and pumped it up. Ready to go.

Yesterday I went for a ride and got a flat. Ripped valve stem. Put in another tube and ten minutes later, same problem. I noticed that the rim tape had bunched up opposite the valve area. That new tube failed about 15 minutes later. After doing some research on the web due to a friend's suggestion, found many threads where the root cause was the tire rotating on the rim when you apply hard braking. When that happens, the tire pushes the tube and since the valve stem is in the rim and can not move, the tube fails there. (Just as if the valve stem was being bent over, but it is the whole tube moving.)

This is a common problem in motocross I guess and never suspected it could happen in our mountain bike set ups, but I am sure this is what was going on. I am going to buy some new rim tape that will have good sticky adhesive and I am sure my problem will go away. The old tape would just slide when I hit the brakes, allowing the tube to rotate with the tire, ripping the valve stem area.

[JanDetlefsen]

I had the same type of issues and it simply took the fun out of biking.

I ended up just buying a new bike, but that was because the bike was pretty old and had other issues.

I'd stop investigating and buy a new wheel(set). It's obviously that there's something wrong with your rims as you have exchanged the other parts of the wheel already. Really whatever it is, doesn't matter, just get new wheels.

[T_Dog]

The cause is hard braking causing the tire and tube to rotate on the rim. This causes a rip at the valve stem.

Solutions:

1.) Don't brake.

2.) Stop the tire from rotating on the rim.

[Ratsima]

Still no flats. Been nearly nine months now. I've changed nothing. In fact, the rear tire tube is still an El Cheapo that I had to buy and install in the field.

I still think I just spent too much time at the wrong end of the "flats per kilometer" bell curve!

[chiangmaiexpat]

Solutions: 1.) Don't brake.

Ah, the Downhiller's credo!

Cheers, X-pat