Torn valve stem - 2nd time same rim

Today I found the tire on my 24" flat. Which is strange because I don’t remember anything being wrong with it the last time I used it. (which was months ago).

When I put some air in it, I could hear and a feel air coming out around the valve stem. The same thing happened on this wheel a few months before. Since the first time I have tried to be more careful when pulling the pump head off. The wheels on both my 29" and 20" have both been fine so don’t think its my air filling technique. Was I just unlucky or is there something about the rim that might be contributing? Looking at the valve stem hole I do not see anything that seems out of normal.

I run my tires at high pressure so the tube is not shifting.

Chamfer the edge of the hole?
Extra layer of duct tape at valve stem hole?
Get a all threaded Schrader valve and use a locknut?
Call it a coincidence and move on?

If you can see where the tube is being abraded you will have a better idea of how to solve the problem. Do you see a cut in the rubber around your valve stem?

The only time I have seen valve stems cut by a rim was when the tube shifted so much that the valve wasn’t running straight through, but at a really severe angle.

I have seen many tubes that had the valve poorly vulcanized to the tube and that resulted in a leak at the seam where the two come together. If this is the case then it’s just bad luck.

I don’t think I would chamfer the valve hole. It would make one side rounder, but the other side would have a knife edge. If you chamfered both edges then you would have a sharper edge in the middle.

It’s hard to find metal Schrader valves on bike tubes, but I have seen them. It might be easier to get a rim grommet, and use a presta valve.

I have had this happen occasionally but never twice in a row like that. What kind of rim is it? Single walled? Is it damaged? I think you meant presta as the threaded alternative. They are slightly more hassle but it would probably solve the problem. A little bit of tape or a ring of felt may help instead.

Is the hole actually on the stem or the base of the stem? It could be at the next spoke hole. I’d make sure the rim tape within a couple inches of the valve stem hole is good.

I’ve seen at least one rim that was just flat enough at the valve stem hole that it would cut valve stems. It looked like someone nailed a curb at the exact wrong angle. I had to replace the rim.

If those aren’t it… I’d try something like chamfering the hole, but with jtrops warning in mind. Don’t cut it down to a sharp edge, just round it a little with fine sandpaper. (Is there a specific name for this?)

If the rim strip hold wasn’t aligned well with the rim hole, I could imagine it pushing the valve stem to one side. Then vibrations might abrade the one side.
But the rim strip would probably have to be way off center, or very tight to create the required pressure.
It’s unlikely, but strange unlikely problems often come from strange unlikely situations.

I agree with going presta. Just get a grommet and make the switch. Presta is stronger. I have a 26" tire on my 24" uni.

happened to me ages ago on my tryall drilled 19", all i can say is be careful when installing a new one.

I agree that Presta is superior for unis. If the rim is already drilled for Schrader, I usually don’t see much point in switching, because the rim has already been weakened. But, if you can find the proper grommet, it could solve the problem. I’d never heard of using Presta on a 24, but apparently there are some [expensive] 24 inch Presta tubes.

Reasons for switching:
[LIST=1]

  • Presta valves are less prone to mechanical problems.
  • Presta valves are easier to inflate because you only have to overcome air pressure to get air in, Schrader valves add spring tension to the problem.
  • It's easy to get a grommet for .50 at the hardware store that adapts the rim, and the rim isn't significantly weaker. The strength issue comes into play when you are running really skinny road bike rims.
  • Presta valves won't ever suffer a rim cut.
  • It's a nice way to run presta valves, because in a pinch you can replace it with either type by removing or leaving the grommet. If you have a presta drilled rim it is much more work to get a Schrader valve into it. [/LIST]

    The Schrader valve is generally more durable than a presta valve, but for bikes, and uni’s that durability isn’t really called for. There is a reason high pressure lines, and industrial equipment use Schrader valves after all.

    You can run a standard XC 26" tube in a high volume 24" tire and get a lighter tube with a presta valve cheaper than a DH tube. It’s a pretty nice fit, and it doesn’t wrinkle the tube on the inside of the tire.

  • or make youre like really easy and go tubluler or tubeless

    Thanks for all the replies. The hole looks like a tear more than a cut but it’s hard to say for sure. The tear is right at the junction of the stem and the tube, but is on the vertical where the rubber gets thin on the sides of the valve stem.

    The hole in the rim strip is well centered over the valve hole and there is maybe 1/32 of rim showing (the hole in the rim strip is slightly larger than the valve stem hole in the rim). But its a cheapy thin rubber rim strip.

    The rim is the standard 2-wall 24" Nimbus rim.

    I’ll take the rim and tube with me to the LBS and see what they have to say about it. Maybe a different (cloth?) rim strip will help. I’d order a tube to get the Presta valve but I’m anxious to use this Uni along with my other two to figure out this whole leaning while I ride thing. I doubt my two small LBS’s in this town are going to have a large 24" tube with a Presta valve but I will check. As it is I have to settle for a 24"x2.125 tube for a 2.5 tire.

    The more I think about it the more I think it is being cut. I am going to just take the edge off the hole in the rim. Not bevel/chamfer/round it, but just break the corner so it’s not an exact right angle and make sure all the other edges are smooth and I will get a better rim strip.

    +1 to what Jtrops said about Prestas. But I think I can make this right without going through the effort to convert to Presta. In other words there is no reason why a Schrader valve should not work right.

    I think you are going about this the right way, I would just sand the hole a little bit to make sure it is not a sharp edge.

    Don’t bother with new rim tape, that is not the problem. I think it was mostly bad luck but getting rid of sharp edges is never a bad idea.

    I chamfered the hole just sligltly and got some cloth rim tape. The cloth rim tape is sligtly smaller than the hole so the edges are more protected. I think between the two I should be golden on valve stems on that Uni.

    When I got the new tube (24"x 1.95-2.125) it hung down loose from the rim by about two to three inches when it was inflated just enough to hold it a little bit of shape.

    I can’t recall another tube hanging down like that. I don’t see it causing a problem and I’ve installed it, it was just somewhat odd to me.

    Presta

    I’d have to disagree with the opinion on the Presta valves. IMO they are rubbish and even more prone to damage than the Schrader valves. On my 29’er I have had to replace 5 tubes all Presta because the valve pulls out of the tube, once near the end of a MTB race and with no spare tube had to borrow a friend’s uni who had already finished the race to finish the race myself. Twice I had just put a tube in and was pumping it up and the valve ripped out. This happened with different makes of tubes as well. Since putting a Schrader valve tube in my 29’er … no more problems.

    The Schrader valves seem to have a thicker stem making them less prone to damage.

    As I said in my other post Schrader valves are more durable. Presta valves are much more fragile. If you’re pulling them out of tubes that’s a different matter though. The tubes themselves may have been deffective. I have seen plenty of Schrader valves pulled out of tubes. At the bike shop I worked at we used to have replacement Schrader valves for just this problem. The stem had a flange on the end that we would push through the hole left by the old valve and then a nut and washer that screwed down to secure it to the tube.

    It sounds like your presta valves were rubbish, but if they were really that bad in general all of the pro bike racers in the world wouldn’t be using them.

    My air pump head needs to be well inserted on the stem to inflate. So it takes a fair amount of pulling to get it back off. I think it was the pulling against the exposed, sharp right angle of the hole that caused them to tear.

    Since the first tear I’ve been careful not to rock the stem back and forth to help pull the pump head off. I try to use more of a pull and twisting motion. Maybe the twisting does it? Who knows.

    But on the other hand I’m not having the same issues on my other two unis using the exact same pump.

    It’s a mystery but not one I’m losing sleep over. If it happens again I will take a closer look at possible causes and solutions.

    I had a similar problem with a rim on one of my recumbents. Had two flats in sort succession, both at the base of the valve stem. Problem seemed to be the pressure pushing the tube out toward the hole for the stem. I cut a piece of rubber about the width of the rim out of a dead tube, poked a hole in it, and ran it over the valve stem, like a tight rubber washer. No problems since.

    I also like the idea of sanding the hole a little to smooth it out; I’ll do that next time I change that tire.

    24" is generally uncommon but it is the normal size for bmx cruisers so you should be able to find a presta valve tube through DansComp or another bmx outlet. I have one that needs a patch and I would happily send it for free but it is a “race light” version and has thinner walls and is therefore more prone to puncture {It has already suffered a staple}. If you want to try it to see if it solves the problem let me know.

    This is the main reason why Presta is better than Schrader for cycle tires; hand pumps work a lot better on Presta valves. I’ve been stuck on the road with a Schrader valve and a Schrader pump which couldn’t pump it up, because with no air in the tire the pump wouldn’t engage the valve stem enough to be able to inflate it, and the tire was too fat to push in the valve from the other side.

    I have had problems with presta valves too. Sometimes the valve wants to stay closed especially at high pressure. Maybe it depends on the pump?..I guess nothings perfect but I don’t use them anymore. In this case it may be the key though.