Pumping tires up before a ride - I keep getting different pressure readings??
07-18-12, 01:51 PM
#1
Senior Member
Thread Starter
Pumping tires up before a ride - I keep getting different pressure readings??
I use my Joe Blow Pro (or Lezyne) to top off my tires before I ride. Great. I pump up to 100 pounds (for example) in the front tire, pump gauge says 100. Fine. I use my Accu tire gauge to double check, and it says 85?? So, I stick the Joe Blow back on, and IT also shows 85. So pump up to 110, check with the tire gauge, and it says 100. Then i put the pump back on, and it says 110?
Does everyone just add more air than their pump gauges say? It worries me to think I may have 85 pounds of pressure when it should be higher!
Does everyone just add more air than their pump gauges say? It worries me to think I may have 85 pounds of pressure when it should be higher!
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'11 Time NXR Instinct / '79 Paris Sport by Moulton
'11 Time NXR Instinct / '79 Paris Sport by Moulton
Last edited by AndyK; 07-18-12 at 02:04 PM.
07-18-12, 01:56 PM
#2
Throw the stick!!!!
I never use two gauges, my pump shows 110 and it works for me. Doesn't really matter if it is really 100 or 120 to me as long as it is consistant.
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07-18-12, 02:25 PM
#3
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07-18-12, 02:46 PM
#4
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I use my Joe Blow Pro (or Lezyne) to top off my tires before I ride. Great. I pump up to 100 pounds (for example) in the front tire, pump gauge says 100. Fine. I use my Accu tire gauge to double check, and it says 85?? So, I stick the Joe Blow back on, and IT also shows 85. So pump up to 110, check with the tire gauge, and it says 100. Then i put the pump back on, and it says 110?
Does everyone just add more air than their pump gauges say? It worries me to think I may have 85 pounds of pressure when it should be higher!
Does everyone just add more air than their pump gauges say? It worries me to think I may have 85 pounds of pressure when it should be higher!
Stick to whichever you feel is more accurate. I found out my pump gauge is off by 5 psi (reporting low) as I have 3 separate gauges which all agree other than the pump.
07-18-12, 02:50 PM
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I set my air compressor regulator to 65 psi, stick the chuck on the valve and keep it there until no more air flow is heard (couple of seconds). Two different gauges tell me that is 60 psi in the tires which is what I run. So now I don't even double check. 65 psi in the hose, let the tire/hose pressure equalize, good to go.
07-19-12, 07:17 AM
#9
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Ah, yes, this makes sense! I knew I was over-thinking it! Thanks.
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'11 Time NXR Instinct / '79 Paris Sport by Moulton
'11 Time NXR Instinct / '79 Paris Sport by Moulton
07-19-12, 10:06 AM
#10
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Road bike tire pressure is like quantum mechanics. The mere act of observing changes the value. With a mountain bike or car tire, the volume of air is much higher so the tiny bit it takes to charge the gauge is relatively insignificant but with a road tire, there's not a lot of air in there to begin with. The volume used to pressurize the gauge is enough to lower the remaining pressure in the tire.
07-19-12, 11:04 AM
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I think it depends on how you check the pressure... If your pump depresses the valve it will equalize the pressure in the hose/gauge. If you instead have a pump system that does NOT depress the valve you will have to equalize the pressure with the pump and add a little to the tube to verify the pressure (my Lezyne was this way). I am now using a automotive type inflator with an N2 tank and $45 gauges (each)... they are accurate down to the lb. I always equalize the hose pressure using the wheel pressure and then add back to the desired pressure. I only check once per ride. (no double double checking).
