Tire Pressure Increases

[WeRetired]

I have a monitoring system, when tires are cold all read outs are in line with my recommended pressures. After about 20 minutes of travel pressures have increased by 15 to 20 pounds. Temps don’t get high, 105 to 110 range. Checked truck tire sensors and they are doing same thing, psi increases 15 to 20 psi. Is this a phenomenon that can be explained to my simple mind. Thanks

[hamm2018]

Originally Posted by WeRetired

I have a monitoring system, when tires are cold all read outs are in line with my recommended pressures. After about 20 minutes of travel pressures have increased by 15 to 20 pounds. Temps don’t get high, 105 to 110 range. Checked truck tire sensors and they are doing same thing, psi increases 15 to 20 psi. Is this a phenomenon that can be explained to my simple mind. Thanks

Temps go up, pressure goes up. What are the tire temps before you start driving? What are the tire temps when you are checking the pressure at that time? I would bet they increase also.

[mdka99]

As the tires turn there is flexing in the sidewall. This causes heat and the heat raises the tire pressure.

[Mr_D]

Normal and taken into consideration when designing the tire.

[WeRetired]

Temps at start up are same as outside temps, I was thinking this was part of the design, just never heard of it before.

[grindstone01]

Yes, the tire PSI will increase with use and now that you have a TPMS, you can fine tune your running tire PSI. My fifth wheel tires are rated for 110 PSI so I try to set the starting PSI at around 100 PSI to achieve a 120 running PSI. On cold seasons, I will start out at 105 PSI. The days of one tire PSI setting for all conditions are becoming the old days.
The key is to watch your tire wear to avoid center wear (over inflated) or outside edge wear (under inflated).

[chunker]

Originally Posted by grindstone01

Yes, the tire PSI will increase with use and now that you have a TPMS, you can fine tune your running tire PSI. My fifth wheel tires are rated for 110 PSI so I try to set the starting PSI at around 100 PSI to achieve a 120 running PSI. On cold seasons, I will start out at 105 PSI. The days of one tire PSI setting for all conditions are becoming the old days.
The key is to watch your tire wear to avoid center wear (over inflated) or outside edge wear (under inflated).

It's unnecessary and potentially bad to be making temperature adjustments based on potential temperature rise. When setting the pressure at maximum to carry the prescribed load, the rise in temperature, and corresponding rise in pressure, is factored into the design of the tire. If you are loaded to maximum weight for that tire/wheel/axle and start off under pressure, you run the risk of overheating and internal damages to the tire. The amount low that you mention probably is a low risk but with RV tires I like to have as much advantage on my side as possible. Sunny side vs shaded side will also make a difference in your starting "cold" temperatures.

[Tightwadted]

When I first installed my TPMS worried about the same thing, found out it is normal for them to go up. Your recommend tire pressures usually say "cold" so don't change them. set to recommended "cold" pressure, then monitor. tires will usually be at ambient temp. first time my Tpms read in the triple digits I was concerned, until I used my IR temp gun and the spare was same temp as the tires on the road. sun + black tire = heat

[grindstone01]

People are strict about a cold PSI setting but accept a 5-20 PSI difference when the tire is rolling down the road. I find it hard to believe that one day a running PSI of 110 is OK and on a warmer day, 130 PSI is also OK. Starting off under inflated only last for the first mile, then the PSI will build up to operating PSI.
A TPMS is a tool to allow a finer tire operation. I find that 120 running PSI works best for me on my rig and I can usually estimate the (seasonal) starting PSI to maintain the 120 PSI operating range.
I have always been concerned that 130 PSI seen on a tire rated for 110 PSI is just a dangerous bomb full of kinetic energy waiting to be released on the next pot hole hit. BTDT and I have replaced 2 cracked rims from a 130 PSI pot hole hit just last year, when I let my guard down one trip! I had even told the wife to look for a pull over spot so I could release some tire air when I hit the expensive pot hole. A lesson learned the hard way on tires and rims that were both rated for 110 PSI.
I would not be too concerned about tire temperature unless you see temps above 150F, then just slow down.

[Spdracr39]

Tire pressures drop in the winter and rise in the summer. Adjust pressures based on an average temp day for the season when the tires haven't moved in a few hours. Set it at what ever the cold psi recommendation is for your load and don't worry about the increase when driving. Do monitor the tire temps though and if one is out of line with the others and the pressure is higher than the others you know something is up. BTW even the sun being on one side vs the other can increase temps and pressures by 5% or so.

[MSHappyCampers]

Don't worry about it! All's good!

[twinboat]

How did we not blow up tires from TO MUCH pressure before TPMS.

We didn't, tires fail from running low pressures or road hazards.

[Hooligan]

Tire pressure recommendations are based on cold temperatures. It is wrong to adjust cold tire pressure to anticipate running temperatures. Tire mfgr's know tire pressure will increase about 2% for each 10 degree rise in tire temperature, and anticipate that when publishing tire pressure tables.. For RV tires in the 80-110 lb range this is about 2 psi/10 degrees increase.
More info here: https://www.tirerack.com/tires/tiret....jsp?techid=73

You may have to adjust tire pressure for summer or winter temperature extremes.

[WeRetired]

Thanks for all of the input, just drive and not worry about it.