set my new 34 inch ridge grapplers at 30psi. that is the pressure when it runs down the street about 5 miles and they level out at 3o psi. When I first start out there at about 26-27. I understand that up here in the real cold weather pressure drops. But when its say 15 degrees outside is the air in those tires really heating up that much that quickly or are my sensors just lazy in the cold?

 

Check them with a tire gauge. Compare the readings with the TPM readings.

 

My experience is that the TPMs are pretty darn accurate hot or cold and when the air in your tire contains more moisture, which can vary per tire, the tire pressure can increase quicker. Nitrogen has become a bit more popular since it doesn't fluctuate as much and is known to be less corrosive on wheels overtime not that I have experienced the latter point. For the record I don't run nitrogen just air.

 

Do let us know what you find by gauging them manually. I am surprised by that type of change. At least that quickly. I know at trackdays with the bike, you have a cold temp and hot temp on tire psi. But that can be a 100 degree swing. They are supposed to be at 165 degrees for a hot check and only have a 3-5 psi change from cold to hot.

 

look like the sensors get lazy when its cold. I checked cold vs when they hit 30 on the display and it started at 29 cold according to the guage 26-27 on the display. When it hit 30 on the display pressures were between 30 and 31 with the tester. So I the real world they vary about 1lb from cold to 5 miles down the road. 2lbs max. For cold I'm talking 14 degrees F. today

 

I could see them changing 2 to 3 psi an hour down the highway as opposed to 15 degrees in you're driveway.

 

The lower pressure you start the more pressure increases (and it will increase faster) from the flexing of the tire as you drive (yes, they flex on smooth pavement) because of the increased friction causing a larger temperature rise.