newbuggy

I just got my first bike with presta valves so I bought a small GIANT pump but it only will fill the tires up to 30-40 PSI but when I just hold my finger on the outlet of the pump it will reach up to 70psi so my question it why doesnt the tire pressurize? p.s. the tires are brand new and will hold at 30-40 psi so there isnt a hole in them or anything like that.

Kimmo

I don't like a lot of cheap presta heads. A cheap shrader head with an adapter works miles better.

Anyway, you really need a floor pump. And you should be able to find a pump for your bike that can manage 100psi.

383

It might be a pump problem - does your pump head have two valves? Put a finger over the schrader head and pump till it flips a switch and air comes out through the presta hole only.

AngryScientist 

you're doing it wrong.

zerocool33

I also do not like presta valves. I have a lot of problems when I connect my pump. I currently have a bontrager after chucking my specialized which had the same problem. It seems like the pump heads or the valves are really finicky. A lot of times I hook it up and try to pump and the it's like the air isn't going into the tire. I always make sure I have the valve all the way open too. Crappy prestas...Or maybe I'm just an idiot, wouldn't be the first time.

newbuggy

it only has one hole and you have to switch a bit on the inside to got from schrader to presta. here a picture.

Homebrew01

After you open the valve, press it once to break the seal ( a quick "pssssss"), otherwise it sometimes gets stuck and won't let air in.

Presta valves have worked fine for decades. Other than a rare manufacturing problem, you're either doing it wrong, or there's a problem with your pump.

Homebrew01

Those little pumps aren't the best, but you should be able to get more pressure. What happens when you hit 40 psi ?

Buy a proper floor pump for home, and save the mini-pump for on the road flats.

newbuggy

Turns out the pump it just too weak for the pressures. so I bought a top peak road morph. I just filled my rear tire from 0psi all the way to 100 psi. So I have found my fix! I do plan on buying a full size pump soon to keep at home. Thanks for the help everyone!
This the morph is alot bigger.

datlas 

Glad you got the problem solved. If you like the good frame pump, you will LOVE a good floor pump. Can you get a refund for the Giant one?

newbuggy

yea if I can find the receipt. But I think it went through the laundry so Im thinking about just craig's listing it.