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Message started by Gary_in_NJ on 04/22/17 at 19:45:26

Title: Strange Tube Issue
Post by Gary_in_NJ on 04/22/17 at 19:45:26

I checked the air pressure in my tires last night. Front showed 32 psi and the rear showed 0 psi. I added air and it still showed 0, so I figured I had a puncture. Today I removed the rear tire from the bike and removed the valve to prepare the tire for removal. As I removed the valve I thought I felt a slight bit of air movement across my fingers. With 0 psi this shouldn't happen.

I grabbed a tooth pick and stuck it into the valve stem (valve is out, on the workbench). As the toothpick makes its way past the base of the stem I got a blast of air. Clearly, the tube is holding air.

I reinserted the valve and I was briefly able to get a reading at 58 psi - so the tube held all of the extra air I added. As I was removing air the flow stopped and I again was showing 0 psi. I removed the valve again and reinserted the toothpick and removed all remaining air.

I refilled the tire and was able to get readings along the way, but when I reached 35psi I stopped getting reading again. I have 35 psi, yet the gauge shows 0 psi. I tried several different gauges. They all work on the front but none work on the rear.

Is it possible that I have an obstruction in the valve stem. How can the valve be removed, with 58 psi, yet I have no outward flow?

Title: Re: Strange Tube Issue
Post by Ruttly on 04/22/17 at 19:56:51

Someone may have used one of those flat repair in a can or Slime that seal the tube when it's punctured. That would be my guess/two cents worth.

Title: Re: Strange Tube Issue
Post by Gary_in_NJ on 04/22/17 at 20:32:52

Good guess, but I installed this tube two years ago.

Title: Re: Strange Tube Issue
Post by verslagen1 on 04/22/17 at 20:46:20

maybe just a rubber glob from when the tube was manufactured.
it's just worked it's way to the stem.

you'll probably have to toss it unless you can hook it and pull it thru.

Title: Re: Strange Tube Issue
Post by batman on 04/22/17 at 20:54:38

Gary,You might try loosening the nut on the valve stem first as this is used to hold the stem in place when putting the tire on ,but then should be backed off to hand tight .If that doesn't work ,instead of a tooth pick,I'd add air to the tube to keep it rounded and run a very short piece of coat hanger just through the valve stem after heating it fairly hot with a torch,any blockage should melt away.It may sound a bit odd but I think the tube is made then the stem added later and there is a small flap of rubber in the base that allows air in but acts as a check valve not allowing air out and that's what you'll be melting away.I also looked at your build pic's ,the right side shows your new front tire ,on the side wall there is a yellow dot that tells the light side of the tire and should be lined up with the valve stem.

Title: Re: Strange Tube Issue
Post by Ruttly on 04/22/17 at 21:46:32

Learn something new everyday, helps keep me from becoming dumb.
I has to be a rubber flapper or some other blockage.

Title: Re: Strange Tube Issue
Post by FL Savage on 04/22/17 at 22:17:22

If you are using a double head tire gauge, like used for truck tires, push the chuck's core stem in on the back side with a small bolt/screwdriver/pen and at the same time check you check the tires air pressure.

Some of these Chinese made double head air chucks and gauges have the stem cores too short, or the springs too stiff. The Schrader stem core and the air chuck/gauge stem core should open each other up. The weaker sprung Schrader core opens easy, the stiffer spring in the chucks core is harder too move and needs to bottom out against the Schrader core to open. If the chuck core stem is a little too short, or spring too stiff, it's hard to get it to bottom out or open to let air to pass.

By pushing on the back side of a double head air chuck/gauge, you can get the chuck core to open.

Title: Re: Strange Tube Issue
Post by Gary_in_NJ on 04/23/17 at 05:23:47

Batman,

The only times I was able to get a reading was when I wiggled the valve stem. I think you are right about the flapper, that explains what I experienced with the tooth pick. Heating a piece of rod a burning out the flapper seems a lot like the old game "Operation". Hopefully I can get this done without the red nose lighting up.

Title: Re: Strange Tube Issue
Post by Dave on 04/23/17 at 05:32:15

You can get cores that have a long stem/spring on the core......this has the potential to hold the flapper away from whatever it is seating against.

Title: Re: Strange Tube Issue
Post by Gary_in_NJ on 04/23/17 at 05:56:34

152E2334252932342F272A35460 wrote:
You can get cores that have a long stem/spring on the core......this has the potential to hold the flapper away from whatever it is seating against.

Good point, the core that is in the tire now is one of the 1/2" long units. I have seen the ones that go deeper. I might try one of those before I go and stick a hot iron in my tube. In fact, I have to unused tubes for my street tracker...I think I'll have a look at those.

Title: Re: Strange Tube Issue
Post by batman on 04/23/17 at 07:39:06

Gary ,If you end up having to use my method ,once the blockage is gone the air should rush out cooling the wire quickly,but the wire should be pulled out just as quickly so the sagging tube doesn't have contact with it, the whole process taking only a couple of seconds.The stem must have a metal lining with threads to except the valve,so the blockage must be at or near the base,the part of the wire you insert should only extend 1/4 inch beyond, and you only need to heat the last 1/4 inch.It's a kill or cure ,but if it doesn't work you have to change the tube anyway.

Title: Re: Strange Tube Issue
Post by hotrod on 04/23/17 at 13:49:55

Buy a new tube. Who knows what bad stuff could be in there.

Title: Re: Strange Tube Issue
Post by Gary_in_NJ on 04/23/17 at 14:05:09

Right now there's only good stuff in that tube - air. Once I get that flapper cleared I should be good. As Batman said, I have nothing to lose.