Pump it up

corblimey

This is always something I've been meaning to ask, but I notice it just before my ride and forget about it afterwards. I've got a foot pump I got from the LBS when I bought my bike, so probably not the best quality (I think it's a BBB). So I put the hose onto the valve, and lock it in place. Once I start pumping though, the gauge moves in jumps as I pump, shooting up and then going back down. I just squeeze the tyre to check if it's hard enough. That's fine, probably not the way it's supposed to work but whatever. But when I finish pump, I can hear rushing out of somewhere (I've always assumed it was the tyre) and it continues until I can get the damn hose off.

Does this sound completely normal to you guys? Should I get a new pump? Could there be something awry with the valve?

Wishbone Ash

You need to remove it quickly to minimise air loss (although there'll always be a bit). Turn the wheel so that the valve is at the top prior to inflation - you can then push the connector downwards to aid a fast removal.

In my experience, guages always go ahead and then fall back during inflation. I think that's normal.

Keep_Her_Lit

Once I start pumping though, the gauge moves in jumps as I pump, shooting up and then going back down.

This happens because each stroke of the pump briefly raises the pressure inside the body/hose of the pump to a level above that in the tyre (the "shooting up" part). It is the pressure difference between the pump and tube which forces the valve on the tube to open. However, once the valve opens, the small reservoir of compressed air in the pump/hose flows into the tube until the pressures equalise (the "going back down" part).

When you've finished inflating the tyre, the remaining compressed air in the pump/hose escapes when you release the adaptor from the valve and that produces the sound that you hear. Unless it's a poor quality pump (or you're being a bit slow in removing the adaptor), you shouldn't lose much air from the tyre when disconnecting it. If you're unsure, just re-fit the adaptor and check the pressure on the pump's gauge. It shouldn't have dropped by more than a few PSI, relative to the value displayed before the previous removal.

In summary, your pump is probably fine. If it can get your tyres to the required pressures, no further action required.

Seaswimmer

it sounds to me like you dont have the pump connector on the valve properly.
If you stop pumping do you still hear air rushing out and does the gauge drop close to zero but tyre is still fairly hard.. If so you need to push it onto the valve harder.

fat bloke

In my experience, sh1t pumps do as you describe. I bought a Joe Blow and it's a pleasure to use. Lock on the nozzle thing and it immediately indicates current and unwavering pressure. Pump away and each thrusting nudges the needle up the appropriate amount. When you're finished release the valve and you get a quick CHH, and that's it. None of your cheap pump incontinence or premature ejaculate.

BostonB

Sounds the cheap pump I had. I replaced it with a Joe blow and its a night and day difference.

mikeoh

I'm very new to cycling sorry for the rookie question....I got a foot pump in aldi lately and just used it for first time...try asall my 90kg may I can't seem to get any more than 60psi into the tyres are the gauges dodgie on these pumps or am I missing something.......tyres feel fine and hard ( bike is a giant defy3)......

BostonB

Buying a good pump is money you'll never regret spending.

TonyStark

fat bloke wrote: »

In my experience, sh1t pumps do as you describe. I bought a Joe Blow and it's a pleasure to use. Lock on the nozzle thing and it immediately indicates current and unwavering pressure. Pump away and each thrusting nudges the needle up the appropriate amount. When you're finished release the valve and you get a quick CHH, and that's it. None of your cheap pump incontinence or premature ejaculate.

+1 for the Joe Blow.

corblimey

+1. After this thread, I went and bought the Joe Blow Sport II which is pretty close to bottom of the range, and the difference between it and my old BBB after market is immense.