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Digital gauge errors
- Thread starter merles
- Start date
globalrider
Alps Adventurer
Same as in car tires.
Nothing special about it other than it does not contain moisture and the molecules are larger...supposedly not allowing them to seep through the rubber...they still need topping up.
I would not waste my time asking for nitrogen fill in my tires.
pglaves
#13338
Actually, the pressure you read with a gauge will go up as altitude increases because the gauge is reading differential air pressure between the pressure inside the tire vs the air pressure outside the tire.
See: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=167
I don't mind being wrong (frequently am) or being corrected. But I hate being stupid enough to not get Paul's reply or even the web page he so kindly included. To my (obviously) weak brain, it would seem that a "cold" tire inflated to 40 psi at sea level would expand a bit at say 10,000 feet if the temperature was the same and the tire had not been run for several hours at either location since there is less air pressure against it. I would think the same number of "air molecules" occupying a larger space would mean a lower pressure on the tire gauge at the higher elevation.
Anyone want another go at relieving my confusion?
Anyone want another go at relieving my confusion?
dancogan
New member
Thanks, Paul. That link was worth reading through. So my conclusion is that tire pressures as read from gauges, or as recommended in the owners manual, are the differential between local or ambient pressure and that in the tire. Therefore, if one is going to do some prolonged riding at 10,000' or so, it will probably be necessary to let some air out of the tires in order to achieve the recommended tire pressure. I had never thought of it that way. Sound right?
globalrider
Alps Adventurer
^ I stupidly reduced the tire pressures in my R65 when I shipped it over to Europe by air. I reduced them by 11 -12 psi. The pressure at ~35K feet is about 3.5 psi.
The cargo area on an aircraft is pressurized to about 8K feet. Brain fart! Duuuh and this from a flight instructor with thousands of hours. Its easier to pressurize a tube than a D section and the fact that they have pets, etc in the cargo hold as well.
As to the volume increasing in the above arguement, percentage-wise, I doubt it makes a difference.
Also note that air pressure gauges can read in PSIA or PSIG.
The cargo area on an aircraft is pressurized to about 8K feet. Brain fart! Duuuh and this from a flight instructor with thousands of hours. Its easier to pressurize a tube than a D section and the fact that they have pets, etc in the cargo hold as well.As to the volume increasing in the above arguement, percentage-wise, I doubt it makes a difference.
Also note that air pressure gauges can read in PSIA or PSIG.
pffog
Small road corner junkie
No completely wrong, The purpose of the pressure is to support the weight of the BIKE, not oppose atmospheric pressure. At 10K feet the difference in pressure is about 4-1/2 psi, not really much, as the psi on the contact patch of a loaded bike from gravity is more like 100 psi!
Another note, yes gauges will read a given pressure higher at altitude, but that varies with the style of gauge, the pencil gauges rely on a spring, dial gauges generally have a metal bladder and springs that are not changed by atm. pressure, so the difference would not be perceivable (PSIG). Some digital gauges may read absolute pressure (PSIA), I am not sure, but the common mechanical ones do not.
As for the theory that the tire "grows" like a balloon, or that bag of potato chips doesn't really apply either as the tires structure and its fibers and metal do not stretch, at normal pressure they are taunt, except where the tire is being compressed by the load around the contact patch, and would not let the tire grow any perceptible amount. IMHO
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re: nitrogen
My auto tire dealer, and friends have mentioned they have seen no apprecible loss of pressure. Tire guy will top off for free if any pressure loss. Just wondering if anyone have tired it in their bike tires. Tryiong to separate fact fiction.
My auto tire dealer, and friends have mentioned they have seen no apprecible loss of pressure. Tire guy will top off for free if any pressure loss. Just wondering if anyone have tired it in their bike tires. Tryiong to separate fact fiction.
osbornk
Old man in the mountains
I bought a car in 2011 that happened to have nitrogen in the tires. I have not had to top up the tires in the 34,000 miles I have driven it. I check the pressure in an insulated garage where the temperature stays pretty consistent. My motorcycles sitting next to it need to be topped off occasionally. It is not something I would ever pay for.
I am good to go with my onboard TPM and a pencil gauge. I must have missed the OCD checkbox...
