Originally Posted by EvilV
I suspect that the hiss you get when you disconnect is due to pressure being lost from the flexible hose rather than the tyre itself. Those valves in the tubes should close tight after the input stroke from the pump surely.
I know that's what the common wisdom says, but I'm almost positive that I'm loosing pressure from the tire. My technique is to pump, disconnect, then reconnect to measure the pressure. It never measures the same; So I overpump and try to disconnect as quickly as possible. However, I don't get a very precise pressure this way.
Originally Posted by cyqlist
I assume you are using Schrader valves?
I've tried using a Topeak suspension pump to pump up 20" tires. It worked, but took about 600 strokes. Might be more feasible for very small wheels like on a CarryMe or Abike.
To prevent losing air when connecting and disconnecting, I modified my Schrader valves by removing the springs, and removed the valve depressor pin from the pump. The Schrader valve then opens and closes with air pressure on each stroke, like a Presta valve. More details here
With this modification I have also gone the other way around and successfully inflated a suspension shock to 130 psi with a Topeak Mountain Morph pump, though it was not easy.
Yes, I'm using Schrader, but I don't think I want to remove the springs. I hate slow leaks.
It really took you 600 strokes using the suspension pump? I currently like to use a frame pump for my small wheels. I find that frame pumps are a PITA for full size wheels, but just right for small wheels. I was hoping that a suspension pump would be like a frame pump, but with more precision. Still, it might be good for topping off.
Do all suspension pumps have bleed valves and anti-leak disconnect? Are those the main features that make them frame pumps?