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A place to ask bicycle repair questions, and for bike shop monkeys to share advanced non commercial wrenching resources (no YouTube self promotion). This is only for repair related topics.

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Tire pressure odyssey, what am I doing wrong? (self.bikewrench)

submitted 8 months ago by Natal to c/bikewrench

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Hello everyone.

I recently got myself a mountain bike from Canyon. It all works, got myself all the gear, pumps and all. And the pressure gage give me a reading of 10 PSI, which is odd because the tires are firm. 10 PSI should be nearly flat.

I have other pumps, including one that works for my car too, which I trust because I cross checked its values with my mechanic.

Here's the odd thing. I got the bike out and plugged it to the car tire pressure device and it also gave me a reading of 10 PSI. I also have a Topeak Shuttle Gage, 10 PSI.

How is that possible? I can't really believe all three readings come from faulty devices so I'm thinking I'm the one doing something especially stupid, or maybe a defect somewhere on the valve/tire but it's brand new, so I think I'm the one to blame. Any ideas where I've been an idiot?

I did open the nut on the presta valve prior to taking measurements.

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[–] j4k3 1 points 8 months ago (4 children)

What kind of pump are you using floor or hand?

[–] Natal 2 points 8 months ago (3 children)

It's a floor pump. This one: https://www.action.com/fr-fr/p/2561081/pompe-a-velo/ I also have a hand pump but I guess it's not particularly useful right now?

[–] j4k3 2 points 8 months ago (2 children)

This is my floor pump against a typical presta valve easily holding ~175psi. You should be able to get well over 100psi on any floor pump against a closed valve.

Take the bike/pump to a local bike shop to compare readings and pressures against a known good source or at least just take your pump(s) and verify against a known good pump.

[–] Natal 2 points 8 months ago (1 children)

There's no risk to using force? Maybe I just didn't push hard enough because I was scared to put too much pressure on the presta and bend it. They look weak.

[–] j4k3 1 points 8 months ago

No risk. Road can go well over 100 psi in road stuff all the time.