Road Bike, Cycling Forums banner
1 - 9 of 9 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
I recently purchased a Bontrager Turbocharger floor pump. Seemed to be pretty good. However, I tried to check my tire pressure Friday night before my Saturday AM ride, and I have no idea what pressure I inflated my tires to. Once I started pumping, the guage had a mind of its own. While I was pushing the handle down, it would spike to between 120 and 160 only to quickly return to a much lower number. I jumped pumped them up 'til they were firm and hoped they would be OK. Does it sound like I bought a lemon?
 

·
Registered
Joined
·
113 Posts
No... i've had that happen to me before with a couple different pumps. Its usually an issue with the pump not being attached to the valve correctly. I think what happens is that the pressure in the pump hose spikes... then slowly equalizes into the tire because the connection isn't good. Make sure you connect the pump to the valve correctly. (I find that it works best if you connect the pump when the valve is at the top of the tire, so the pump head latches on vertically rather than horizontally.)
 

·
Registered
Joined
·
14,776 Posts
It's probably okay

Was the "much lower" number it settled on in the range you expected? Did it get a little higher with each stroke? The behavior you describe is basically normal with presta valves, since the pump has to get the pressure higher to force the tire valve open, and then the indicated pressure will drop back to correspond to the pressure in the tire. If it stays at the high reading for more than a fraction of a second that may mean a slightly sticky check valve in the pump, but as long as it does move back it's probably inflating the tire properly.
 

·
Registered
Joined
·
10,161 Posts
??

Did you first loosen the nut, then tap the top of the stem to break the air seal (letting out a brief burst of air), before you put the pump head onto the valve stem? If you don't do that, it might take 160-200 psi to break the seal. Once the seal is broken the pressure will drop to whatever is in the tire.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #6 ·
Basically, I was just unsure about which number to use. My tires have a max PSI of 120. I'm also running 700 x 28 tires. I didn't want to risk a puncture, so I had to guess by feel. If the guage settles in the 70 to 80 psi range, is that what's in the tires vice the 130 it spikes to when I'm pressing the pump? My old pump, which my wonderful children broke a few years ago, didn't do this.
 

·
Registered
Joined
·
10,161 Posts
yes...

Any gauge that's registering properly will spike very time you push down. The only reading that matters is what it says when you quit pumping.

The proper range of pressure is often written on the sidewall of the tire. Even a 700 x 28 would usually need at least 85 psi, but it varies with the brand and how true the sizing. If you don't use enough pressure, the tire will be prone to pinch flats.
 

·
duh...
Joined
·
9,749 Posts
C-40 said:
Did you first loosen the nut, then tap the top of the stem to break the air seal (letting out a brief burst of air), before you put the pump head onto the valve stem? If you don't do that, it might take 160-200 psi to break the seal. Once the seal is broken the pressure will drop to whatever is in the tire.


bingo
 
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top