That's next, but I'm not in a position to drop 70 bucks right now.
Lennie was right, I checked with a caliper and the old ones are 80 and the new ones are 90. Not enough to be able to see but plenty to make them bind up. I'll go to Fastenal tomorrow and get the right ones, or if I can't I'll find a 10-24 tap and chase the holes out. At least the mystery is solved.

Flexible valve extensions are leak-prone.

Best is a metal stem of the proper length and curvature.

Next best is a tubular brass extension from Patch Boy or Gempler's, held on with blue Loctite. CW sells some curved metal extensions that are OK if put on with Loctite. Be careful, though, as standard valve caps might not fit them.

Next best is stick with the short stock stems and use an airing extension and long gauge or just screw an extension on to service or check air. A hexagonal valve cap is easy to remove and replace with a nut driver. One extension and a driver does it.

If you have rubber valve stems, do you know their age and type? There are two different types of rubber stems. One is rated for high pressure and one is not. The HP one has a 90-degree shoulder inside, and the unstated pressure one has a rounded shoulder.

I second El Segundo bill's motion, re: leak-prone flex extensions. Been there, done that.

Tha tires were put on by the local experts in RV and truck tires and I was told everything needing replacement was done. Of course that was 5 years ago but I've never experienced any loss of pressure in any of the tires. I think I'll just stick with what I have and use the trucker gauge that I've always used. Even with the new covers all the valves are accessible.

Hey,

That's good.Which tires you are using?

You mentioned about covers, May I know which 5th wheel cover you are using?