Air pressure question

[racefn]

I recently added TST sensors, I have always run air pressures from tire chart, in my case 105 front and 90 rear, I noticed on trip from Indiana to Az last week air temps in front tire rose about 18 lbs. and in rear a little less, is this normal?, I lowered cold pressures in morning to keep pressures down, now I'm sure that was the right thing to do, outside temps probably ranged from 40-60 most days, when you set pressures should they be running temps or cold temps, i have always assumed cold temps, but after seeing how much they rise, not to sure anymore.

[luvlabs]

It is normal for your tire pressure to increase as the tire warms up. This is not going to hurt the tire.

You should continue to set your cold pressures to what is appropriate for your tire loading (110/90 psi). Lowering the cold pressures was wrong and you could be damaging your tires by running them at too low of pressure.

[CLIFFTALL]

Originally Posted by luvlabs

It is normal for your tire pressure to increase as the tire warms up. This is not going to hurt the tire.

You should continue to set your cold pressures to what is appropriate for your tire loading (110/90 psi). Lowering the cold pressures was wrong and you could be damaging your tires by running them at too low of pressure.

X2
Cliff

[racefn]

Thanks, I knew they would increase, just surprised at the amount, as my car only moves a couple of pounds, max tire pressure on sidewall says 120lbs and running temps were over, thats what happens when you get new gadgets that beep and flash, Its funny how when I didn't know, I wasn't worried.

Thanks again
Bob

[wb7auk]

It is normal when the tire heats up to increase the hot air pressure 15 to 20 lbs.
As posted changing the cold pressure less means the tire is under inflated not good.

[stik]

Originally Posted by racefn

Thanks, I knew they would increase, just surprised at the amount, as my car only moves a couple of pounds, max tire pressure on sidewall says 120lbs and running temps were over, thats what happens when you get new gadgets that beep and flash, Its funny how when I didn't know, I wasn't worried.

Thanks again
Bob

I am pretty sure if you look closely at the tire that the Max pressure of 120 lbs refers to max COLD pressure.

[Gadget63]

Don't make the same mistake as I did when I installed my monitoring system. Don't go chasing tire pressure. Set them up when the tires are cold to what you have been doing and to stop that annoying alarm going off, set a higher maximum pressure. All tires heat up and expand when driving for a while. It is better to run a tire with more air than less. Less causes blowouts, trust me I know!

[racefn]

Originally Posted by Gadget63

Don't make the same mistake as I did when I installed my monitoring system. Don't go chasing tire pressure. Set them up when the tires are cold to what you have been doing and to stop that annoying alarm going off, set a higher maximum pressure. All tires heat up and expand when driving for a while. It is better to run a tire with more air than less. Less causes blowouts, trust me I know!

I am hearing you and the others loud and clear, Thanks Again

[sparkydog]

On a recent trip in 45-50 degree temps, my tires fluctuated as much as 12-15 lbs, lower in the rain, higher on dry pavement. Your pressures are normal, as said before always set pressures cold, based on manuf. recommendations, or actual wt. if you happen to weigh it.

[vsheetz]

Tires pressure will also vary by several PSI whether they are in the sun or not.

I too was somewhat surprized at the variences I was able to see once I installed a TPMS.

[Zoafan]

Side question, for those of you towning a trailer what PSI do you keep your tires at?

[Gadget63]

Originally Posted by vsheetz

Tires pressure will also vary by several PSI whether they are in the sun or not.

I too was somewhat surprized at the variences I was able to see once I installed a TPMS.

Yes I was amazed at that finding too! Although all tires had the same pressure before starting out, the side of the rig facing the sun had higher air pressure and that included the tow dolly too!

[Mr_D]

Originally Posted by stik

I am pretty sure if you look closely at the tire that the Max pressure of 120 lbs refers to max COLD pressure.

And it's not actually the maximum pressure! It's the MINIMUM pressure required to support the MAXIMUM weight rating of the tire. It's spelled out in the manufacturers literature

From page 2 of the 06/07 Michelin RV Tire Guide: "If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."

BTW: this is for truck and large MH tires. Smaller tires like on cars it is the maximum pressure the tire should ever have.

[DAN L]

Originally Posted by racefn

Thanks, I knew they would increase, just surprised at the amount, as my car only moves a couple of pounds, max tire pressure on sidewall says 120lbs and running temps were over, thats what happens when you get new gadgets that beep and flash, Its funny how when I didn't know, I wasn't worried.

Thanks again
Bob

you should notice that your rear inboard tires will run hotter, thus pressure will increase more than the outboard tires. this is normal.