10° F temp change = 1 psi.


1000-feet of altitude change = [approx.] 0.5 psi.


Keep in mind that when measuring tire pressure that your gauge is referencing [comparing to] the ambient air pressure, ambient being "zero". Ambient can be all over the place depending on altitude and current barometric pressure.

 

Back in the days of race bikes running bias ply tires, it was said that the difference between cold tire pressure should be less than 10%. So...36 cold and under 40 hot all was well and expected. No rise meant too much cold pressure and more than 10% meant too low cold pressure.

That being said, if you do not have a good calibrated tire pressure gauge then you may not be able to distinquish 10% differential accurately. TPMS are horrible inaccurate.

 

Too much technology, too little knowledge. Tire manufacturers have been making tires for a long time. They know about hot summer blacktop and elevation changes. If the tire manufacturer says X pressure cold (say 40 psi) he already knows that the pressure will go to 50 or bit more on a hot summer afternoon high speed run. That was taken into account when the tire was engineered. The enemy of tires is heat, not pressure. If you LOWER the cold pressure because the hot temp pressure seems scary, the tire will flex more and get even hotter, at some point exceeding the temperature the manufacturer designed for. Then the tire fails from initial LOW pressure. I run all of my tires at the max allowed figure embossed on the sidewall, at less than the max load my tire will run cooler than the same tire at the "recommended" pressure for my machine. Lower pressure seems to encourage cupping also. The max on the sidewall also seems to slow cupping even more than the "recommended" pressure. I just accept whatever the tread wear rate is for that higher pressure. When the question comes up, how many miles did I get from tire X, my mileage to wear out is right up with the top claims. Even with automotive tires, my experience is that the max sidewall pressure provides even wear across the tread face. Perhaps radial ties are less sensitive to pressure for center or shoulder wear than were bias tires.

Your machine, do what you want, remember you happy BEFORE TPMS came along. By knowing that the manufacturers had all of this figured out long before you bought your first tire and before TPMS, you can be happy again, even with the data overload from TPMS.

 

The question that should have been asked was, what should your tire pressure be when refueling?

 

My rear tire routinely increases 7 psi on stable outside air temp and altitude!

 

400 ft to 13000 ft. 29 degrees F to over 100.

If you set a tire in the cold morning before the sun comes up and your still in the low lands, then ride all day through high mountain passes, your going to run some pretty high pressures. Nitrogen doesn't help.

 

Yep.


.

 

And you are keeping it a secret.

 

No "solid answer" for that either. Are you stopping for gas after an hour of urban stop and go low speed driving or after 2 hours of uninterrupted interstate cruising at 80 mph? Worrying about hot tire pressure after it has been properly set according to manufacturer's procedures and value is pointless. The tire is built for whatever happens during normal use.

 

You're not actually going to ride 'all day', presumably take a break at some time? Check 'em again after they have cooled down. However if you reset them they will obviously go down as you descend back to home.

Man has been riding/driving through mountains since the inflatable tyre was invented. Personally I wouldn't spend too much time on this. Have you phoned or emailed your tyre maker for their input?