MTFCA Forum

I have a tire issue I never ran into before. I have a good 21 inch tire that was low in air. I pumped it up to 35 Lbs and all was fine. I then checked the pressure with a tire gauge and the gauge read 0 PSI. I checked and no air will come out or go in. Same when I removed the valve from the tube. Tire is aired up but no air will go in or come out. I gently pushed a wire up through the stem and it felt like it went into the inner tube but still no air in or out. Very strange. I hate the thought of taking the tire off the split rim. Guess I have no choice.

Anyone run into this before?

Tim.

If you have trouble with the valve stem, it may need to be replaced with an original brass stem. That will involve removing the tube. In the meantime you can get rough with it and perhaps save having to dismount the tyre. Use a stiff rod to poke up the stem, sharpened like a screwdriver. Mark it for length to indicate if it has penetrated far enough to go into the tube. Perhaps you are up against some balancing beads or leak stopping goo.

Allan from down under.

Thanks Allan, no beads or goop. I put the tire/tube/flap myself 10 years ago. I suspect it has something to do with the flap. Since I can't get the air out of the tire I can't get it off the rim. I pushed a wire up through but there is something hard blocking that I can't penetrate. I will drive around in the field with the partially inflated tire to see if it breaks free and if that doesnt work I will drill up through the valve stem. Frustrating!

Tim

I had one do this many years ago. Ran a small drill bit down the stem and got air in. Never found what problem was, didn’t care after got air in and out. Dan

I suppose this is a silly question, but have you removed the valve core from the stem?


The tool at the bottom (core wrench) is for installing or removing valve cores.

Hi Steve, there are no silly questions so thanks. Yes I did remove the valve with the tool. Still no air out. Very strange. I went back out to the garage and put together a lever to allow me to push down on the valve stem into the tire hard and the air came out. So now I can get the tire off and see what happened. My guess is the tire bead closed around the valve stem and squeezed it off. By pushing down I pushed the valve stem past the pinch point. After I get the tire off I will report back on my findings

Tim

It was not likely to be a bead pinching the stem on a straight sided tyre that fits a split rim. There is a considerable gap between them when aired up. We await the tyre dismount for the verdict. Certainly a strange one!

Allan from down under.

I had this occur once on a rear wheel. The tire had rotated on the rim and the tube was kinked or folded over at the valve. Removing the valve core and drilling through the stem might drill a hole in the folded tube.

I finally got around to taking the tire off, It appears its the same problem as described above, the tube shifted and the valve stem got pinched closed. The tube stem was torn likely when I pushed it back into the tire. I had no choice because I couldn't get the air out any other way. I am not sure if the flap or the rim pinched the stem but the stem coming through the wheel appeared straight. New 21" tube with metal stem this time was ordered. No problem getting the tube, tire and flap off the split rim.

Tim

Maybe the beads needed a little notching for a rubber stem.
I know some claim notching isn't necessary. The last tube I replaced a metal stem with a rubber stem clearly needed the notching to not pinch the stem. The old ,modern, vulcanized metal stem was tight against the beads. Not good for the larger base of a rubber stem. Unfortunately the pinch/leak was next to the thick vulcanized stem pad.
Not in a place I would try to patch. We did recycle it into a flap for later use.

Edit: Doesnt apply to 21" tires. Only clinchers.

The tube shifting in the tyre happens when the tyre is underinflated. The valve stem hole in the rim and the same in the felloe will tend to hold the valve stem vertical, so when the tube wants to shift it will tend to tear away from the stem. The same can happen with metal stem tubes. The correct tyre pressure is the answer.

On a 21" flat based split rim, the tyre beads are nowhere near the valve stem. Besides, there is very little material around the wires in the bead that you could notch anyway.

Allan from down under.