uh... inflating tires and pressure gauge...

[aeiea]

really embarrassing question.
But I'd rather be embarrassed than... deflated?



Usually with my mountain bike, I pumped til the tire felt firm, and off I went!

Now with my new road bike, I want to get precise. I got a new standing pump (my old one only had schraeder valve option) which also has a built-in pressure gauge.

My tires felt firm-ish, but after a 25 mile ride I figured I'd add some air. My tires say min 100 psi max 125 psi.

So I took off the cap, unscrewed the nut, attached the pump as the instructions specified... and the pressure gauge read at 0.

So I started pumping... went to 20... 40... 60... 70... and then it got too hard to pump anymore. Plus I was too scared I was doing something wrong and the tires would explode.

Am I doing this right? Is this pressure gauge only reading what I've added? After I stopped, I felt the tires and they felt super firm... so why is the gauge only saying 70? Is it defective? Do I just not know how to get correct tire pressure?

[Eden]

Here's a possibility. You may not have broken the seal that the valve sometimes forms. You can push the valve down and let a tiny bit of air out before you put the pump on or just listen for the "click" that lets you know the air is actually going into the tire and its not just pressure building up between the pump and valve. You won't always hear it click because it doesn't always seal up so tight that you need very high pressure to get it going.

[aeiea]

Thanks Eden.

I felt for sure I broke the seal on both tires but maybe I'll try again. I think I didn't hear the click, but I'll give it another go tomorrow.

Maybe I didn't put the pump on the valve properly/fully ... was too afraid of breaking the delicate looking presta valves!

[Kalidurga]

Speaking of pressure gauges, I hope no one minds if I add a question to this thread...

I've got a 10 or so year old Joe Blow pump with gauge, and a hand-held tire gauge that I picked up just a couple of years ago. The hand-held gauge consistently measures 10psi below the pump gauge. Which is more likely to be accurate?

[OakLeaf]

I don't think it's possible to say which is more accurate. You just have to find a known accurate gauge to compare them against (or at least compare one of them against a known accurate gauge, then compare that one against your other one).

If your handheld gauge is Schraeder valve, you should be able to find an ISO-certified auto or truck facility with an accurate tire gauge to calibrate yours against. Be sure it's ISO-certified though. Lots of auto dealers and tire shops don't bother to calibrate their gauges at all.

Tire service people at motorcycle races (international events excepted) are usually happy to calibrate a tire gauge, when they're not busy with the race tires. Probably would be the same with auto club races. I'm not sure how tire service works at major bici events, anyone?

[Kalidurga]

I think they're both Schrader compatible, though I use them for Presta. I wonder if my auto repair place would be able to calibrate one or both for me... Might have to ask about that the next time I get an oil change. Thanks for the idea!