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Old 08-17-08, 07:04 PM   #1
bernmart
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Floor Pump Question

For two years now I've been using a humble Topeak Joe Blow floor pump with perfect satisfaction. Last week or two, though, one or both of these things happen when I pump up my tires (which I do before almost every ride):

In mid-pump the chock pops off the valve (presta). If that doesn't happen, or before that happens, on the downstroke the gauge moves up normally, but then falls back to lower levels. At best, I keep pumping until it seems like there's enough air, and then pop the chuck off.

My guess is that both these symptoms come from a common cause, but I don't know what. I'd hate to buy a new pump when the old one has been doing fine.

Thanks in advance for all advice and suggestions.
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Old 08-17-08, 07:44 PM   #2
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Sounds like the o-ring in the pump head is worn out, causing the chuck to sometimes pop off and other times allow air to escape. You should be able to rebuild or replace the pump head. Check out Topeak's website for more info or maybe email them.
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Old 08-17-08, 07:47 PM   #3
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It's not an Oring in there but you got the right idea. It's actually a special molded sleeve with a flange on it. But likely it is worn out from going on and off the threads so now it's not holding right and is leaking.
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Old 08-18-08, 04:59 PM   #4
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That clicking sound is probably the presta-valve's seal opening up from the pressure. When you finally build up enough pressure in the pump-reservoir to overcome the valve's spring, it opens and air flows in. What happens a lot of time is the valve isn't unscrewed enough and it's not tapped slightly to give an initial PFFSst to unlock the seal.
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Old 08-18-08, 05:30 PM   #5
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Quote:
Originally Posted by A.Winthrop View Post
Hi,

My ancient Medai (Schwinn branded) floor pump does similar
things. The head pops off but only rarely and I suspect
that's my fault due to careless attachment.
.
My bigger problem is the gauge needle going up quickly with
each stroke but without pushing any air into the tire. Then
there is a little clicking sound, the needle drops down a
bit and then air does go in with each stroke of the pump.
You can try to replace the interval chuck parts or replace the entire chuck head, any brand will do. Easy fix is to get a new chuck head with or without a new hose. You will probably need a small hose clamp or two. If your LBS doesn't have such clamp they are available at auto parts and hardware stores. This type of clamp is about the diameter of your little finger.

The click is the presta valve opening. Before you start pumping "burp" the valve with your finger to unstick it.

Al
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Old 08-18-08, 05:32 PM   #6
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Quote:
Originally Posted by A.Winthrop View Post
Hi,
.
My ancient Medai (Schwinn branded) floor pump does similar
things. The head pops off but only rarely and I suspect
that's my fault due to careless attachment.
.
My bigger problem is the gauge needle going up quickly with
each stroke but without pushing any air into the tire. Then
there is a little clicking sound, the needle drops down a
bit and then air does go in with each stroke of the pump.
.
That clicking sound is music to my ears because too often
I don't hear it and I have to pull off the pump head,
let out more air (I've already done that the first time)
and start again from scratch.
.
Usually, I do hear the clicking sound and all is well. Sometimes
air is pushed into tube from the start - without first reaching
high pressure, followed by the clinking sound and the drop
of the needle - and then all is well. That's a GREAT day!
.
I suspect this problem is due to a sticky, pressure-sensitive
valve of some sort in the pump's researve tank. The tank
is pressurized, I suppose, as a buffer against the tire
pressure to prevent back flow of air pressure into the
pump (a good thing when a guy thinks of the possible
consequences of that pump handle shooting up at high
speed when he's standing over it). Someties that one-way
valve sticks, preventing pressure from passing from one's
pump effort into the tank and on to the tire and sometimes
it doesn't stick. And sometimes when the pressure reaches
a certain point in the tank with none passing into the
tire, a stuck valve comes unstuck with that lovely little
clicking sound, and all is well.
.
All the above is no more than theorizing but if someone
out their can confirm and then suggest a solution, I'm
all ears, and not just for clicks.
.
I had this problem for awhile with my pump. It ended up being that I wasn't pushing the head of the pump on to the valve far enough. Once I did that, the problem was solved.... Just a thought, but it worked for me...
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Old 08-18-08, 05:32 PM   #7
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Quote:
Originally Posted by bernmart View Post
For two years now I've been using a humble Topeak Joe Blow floor pump with perfect satisfaction. Last week or two, though, one or both of these things happen when I pump up my tires (which I do before almost every ride):

In mid-pump the chock pops off the valve (presta). If that doesn't happen, or before that happens, on the downstroke the gauge moves up normally, but then falls back to lower levels. At best, I keep pumping until it seems like there's enough air, and then pop the chuck off.

My guess is that both these symptoms come from a common cause, but I don't know what. I'd hate to buy a new pump when the old one has been doing fine.
Check with your LBS for replacement parts. Easy fix is to replace the chuck head with or without a new hose, any brand will do as long as the chuck is a presta. See my other post about hose clamps.
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