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Today I got my new bike pump. It is a two-way pump with pressure gauge, up to 100 psi, that I bought cheaply over the internet. When I tried to pump up my tire (Schrader valve) it seemed to be working, I mean, it pumped my tire. But the problem is that the gauge shows 20-25 psi even if I pump more and more until I can hardly squeeze the tire. Also, when I let the air out, it shows less than 10 psi. So the range is 5-25 psi let's say... On the other hand, when I place my thumb on the pump valve and squeeze the pump, it shows 30-40 even 50 psi (I can't hold it to higher psi range).

What can the problem be? Is it possible I am not putting the pump in the right position when I am pumping the tires?

Thank you in advance!

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    I'm hoping that changing manometer to pressure gauge is helpful and not just a reflection of my lack of knowledge of English usage outside of the US – I think of a manometer as being one of the 'U' shaped gauges where you read a column of liquid to measure pressure.
    – dlu
    Nov 25, 2015 at 17:15
  • What happens if you take the pump off (after pumping the tire up so that it is reasonably hard) and then put it back on? Do you get the same reading? Also how big are your tires? One difference between trying with a tire and blocking with your thumb is that the volume of air involved is much smaller.
    – dlu
    Nov 25, 2015 at 17:18
  • Yes, when I take it off it shows 0 psi. When I put it again it shows again 20 psi...
    – SuperMan
    Nov 25, 2015 at 17:32
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    Our chat session suggests its a dodgy gauge. Recommended to return pump for replacement, but its a cheap website purchase with no return policy. Suggested to test tyre pressure against a known good air pressure gauge and compare readings.
    – Criggie ♦
    Nov 25, 2015 at 20:51
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    A cheap mechanical dial gauge is 10-15 dollars. It is a good idea to check any gauge against a couple of other probably accurate gauges (possible on pumps) at home and/or a bike store. When I did that I discovered my home pump (from P******e) was showing 15 psi over true psi, but the mechanical dial gauge is got for $10 was accurate.
    – Craig Hicks
    Nov 29, 2015 at 1:22

1 Answer 1

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I have a Topeak "Road Morph" mini pump on my bike, and the pressure gauge on that is at best a distraction. The display is a bit of plastic sliding in a tube, so there's a lot of friction and that makes the pressure reading unreliable. It can stick anywhere, but usually it reads low, like yours does. That makes it useless for anything other than "is there air in my tyre", which I can answer more easily by squeezing the tyre.

road morph bike pump manometer on road morph bike pump

So it's likely that the reason you're having problems is that your pump is a cheap version of mine, and it works even less well than mine

The effective pressure gauges that I've seen are all dial gauges, and there are not many mini pumps that have those. Normally they're found on floor pumps like this: enter image description here

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