Originally Posted by
Walpurgisnacht
I have a question about this too, actually. My floor pump's gauge behaves a bit strangely, but it's my first floor pump so I don't know if it's normal. If I fully deflate the tire and start pumping, the pressure increases with each downward stroke of the pump. Once I reach around 60-70 psi (on tires rated for 95 psi) the needle no longer moves regularly. It becomes harder to pump around that point, too. If I pump a few more times then the needle will jump to around 80 psi. I've tried pumping a bit more (in an effort to get it to 95) but the needle doesn't move. The tires already feel rock-hard by that point, so I tend to stop pumping. My concern is that I may be over-inflating the tires. I'd prefer to have an accurate measure of the pressure rather than to go by the "pinch test," particularly since the pump has a gauge.
So what's the verdict? Cheap or faulty floor pump? Or just the way these pumps work?
Pumping will always get harder as the pressure goes up because the force needed to move the piston is equal to the pressure X the piston's area. Likewise the gauge will show that same spike and settle pattern I described earlier. But it should show incremental increases in the sense of 3 steps forward and two back with each stroke. A gauge that stays in one place then jumps, is sticking for some reason, and that means it's not going to be accurate or reliable.
I suggest cross checking the pump's gauge readings against a hand held gauge to get a sense of what may be happening.
Another way to check a built in gauge is by putting the thumblock onto something solid to plug the hose. Now, as you press the handle the gauge should rise smoothly and steadily as you advance the piston. You might have to do two or three steps to bring the hose to high pressure, and there's a backflow check valve at the base of the pump so air won't flow back out of the hose.