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Old 01-25-07, 08:41 PM   #1
BloomingCyclist
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Tire Pump Guage Accuracy

Are there any tire pumps with guages or separate guages that are known / guaranteed to be accurate to within a pound or two psi at the 100 to 140 psi range? I see 10 psi difference between my Topeak Joe Blow Turbo and my Trek - I have no idea which one is closer to being correct but I'd really like to know if I am riding on 130 psi or 120 or 140 when I think I'm riding on 130.

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Old 01-25-07, 09:40 PM   #2
djsincla
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I use the Topeak Twister which has a digital readout accurate to .5 psi. No idea if it's "calibrated".

http://www.topeak.com/2007/products/...mps/twista.php

Throw the Trek pump away.

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Old 01-26-07, 06:14 AM   #3
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How are you comparing the two pumps? If you are pumping with one pump, and then checking the pressure with the other pump, you will be loosing tire pressure to fill the pump you are reading with.

I guess If you inflate the tire with pump A... and measure with a seperate gage. Then inflate with pump B and measure with this same seperate gage, and there are consistance differences, you might have a problem.

glenn
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Old 01-26-07, 06:57 AM   #4
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Just an alternative point of view on bicycle pumps and tire pressure....

I look at the pressure gauge on most pumps like I do body weight scales; they're usually a bit off.

At home and with my own scale, it really doesn't matter how far off it is because all I'm looking for is confirmation that when I stand on the thing I can see if there has been any change since the last time.

The same thing goes with my pumps at home, they all read a bit different but I've figured out what number to look for on each gauge to know that I've gotten my tire pressure where I like it, which I can usually verify by pushing my thumb into the sidewall of my tire and then confirm as I / we ride. Now, to be fair, I pretty much use just one of the three pumps I have laying around and have forgotten how the other two read. So, when I pump up our tires I know that the gauge reads about 10% low and with that in mind I know that I'm shooting for a reading of X every time I pump up a given tire, e.g., Debbie's tires run at something around 120psi, mine a little higher and the tandems even higher still.

Yeah, it would be nice to know exactly what it is and there are some really good gauges out there that do that. However, until you figure out how to get a valve chuck off with a nice crisp "pop" you'll always be losing a few psi from whatever you saw on the gauge before you pulled the chuck off the tire. As someone else noted, every time thereafter you check again with another gauge you'll lose additional psi and, unlike a car tire that has huge volume and low psi, a bicycle tire inflated to 130psi looses a lot of that pressure in an instant.

Bottom Line: Close-enough is usually good enough.
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Old 01-26-07, 10:42 AM   #5
merlinextraligh
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Quote:
Originally Posted by TandemGeek
Bottom Line: Close-enough is usually good enough.
+1.

Moreover as long as its consistent, that's enough. Pump to the pressure that gives you the ride quality you like, and doesn't result in pinch flats. It doesn't matter what that number is nominally called on the guage.

More often than not I use the thumb guage.
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Old 01-26-07, 11:44 AM   #6
cornucopia72
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Whenever we had a flat on the road and had to use the frame pump and the "thumb gauge" I would guess 120 psi only to get home and check that the pressure was only 80 psi. Maybe it was more sore arms after 120 strokes or not wanting to keep to group waiting. We love CO2 inflators!!
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Old 01-26-07, 01:04 PM   #7
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Quote:
Originally Posted by BloomingCyclist
I see 10 psi difference between my Topeak Joe Blow Turbo and my Trek - I have no idea which one is closer to being correct but I'd really like to know if I am riding on 130 psi or 120 or 140 when I think I'm riding on 130.
My Joe Blow was exactly 20lbs off compared to two hand gauges and one at a bike store. I called them and they sent a replacement head which was also exactly 20lbs off. I gave up and now always add 20lbs to the gauge on the pump. Maybe they are concerned about people pumping up tires too high.
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