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Old 12-01-07, 10:04 PM   #1
makeinu
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suspension pump for small wheels?

Can anyone recommend a pump with a bleed valve for small wheels? I find that I have a hard time precisely setting the pressure on my small wheeled bikes.

They take too few strokes to pump up and I lose too much air when I connect/disconnect. I think that perhaps a suspension pump might fix the problem.

What do you guys use?
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Old 12-02-07, 06:17 AM   #2
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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.
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Old 12-02-07, 06:30 AM   #3
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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.
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Old 12-02-07, 11:45 AM   #4
makeinu
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Quote:
Originally Posted by EvilV View Post
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.

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Originally Posted by cyqlist View Post
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?
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Old 12-02-07, 07:40 PM   #5
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Originally Posted by makeinu View Post
Yes, I'm using Schrader, but I don't think I want to remove the springs. I hate slow leaks.
Almost all of the Schrader valves I've used held air okay without the spring. In the case of those that don't, all it means is that the valve cap ends up holding the air instead of the valve - still no leak, until I unscrew the valve cap, when just a very small puff of air is released as the valve recloses. Of course I use good valve caps with a rubber gasket, not the cheap plain plastic ones.

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It really took you 600 strokes using the suspension pump?
It actually took 650 strokes to inflate the tire using the shock pump, 75 strokes to inflate the tire with the Mountain Morph, 100 strokes to inflate the air shock with the shock pump, and 12 strokes to inflate the air shock with the Mountain Morph.

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Originally Posted by makeinu View Post
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?
I don't know about all suspension pumps, only the one I have which is a Topeak Shock Master Blaster. I would say the main distinguishing feature of suspension pumps is that they are made to pump less volume and higher pressure.
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