Tire Pressure Increase On the Road

[rameyer84]

Just got a TST tire pressure monitor and tried it out last weekend on a short trip. Have Sailun tires on an 18,000 lb. fifth wheel that registered 106 to 108 psi before hitting the road. It was a sunny day with temperature around 95. I expected the pressures to rise as I went down the road, but they went up 10 to 12 psi per tire. All four trailer tires were registering 120 to 122 by the time I got to my destination an hour later.

Question, is this normal increase for tire pressures on a hot day?

[Mr_D]

Yes.

[rameyer84]

Originally Posted by Mr_D

Yes.

Thanks. Sometimes ignorance is bliss.

[Bob_C]

Mine rise that much.....

[road dogs]

My 5th wheel tires are 80psi, I always keep them at 75 before a trip for a little expansion headroom.

[twinboat]

What did we do before TPMS temps ?

Tires don't fail from over pressure.

[Do26]

From Roger Marble and experience... The inflation pressures are for ambient. Wheel and tires can handle the heat and pressure buildup during normal usage. 2% pressure increase per 10 deg temp rise. So a 10 to 15% increase can be normal. 100 degree increase (20% psi) is likely acceptable if not due to under inflation.

Tpms defaults to 158 deg for warning level... No need to leave "room" for pressure increase, set based on tire resting ambient.

[PAtrailtrim]

Yepper, this is normal. Rise impacted by ambient and road temperature. Approximately 8 to 12 psi for me.

[grindstone01]

My Sailuns do the same thing. I will start out at 105 PSI and have seen them go up to 128 PSI on a hot day.
I have been challenged many times for this, but I will try to keep my rolling PSI down to around 120 PSI which may require letting some air out.
My opinion/thought is that the tires running at 128 PSI are overinflated and besides wearing the center thread, they make for a hard ride on the trailer.
Don't be afraid to fine tune your tire PSI now that you know what they are doing while going down the road. Just because the old school said to set the tires at cold temp and leave them alone, doesn't mean it can't be improved as better tools (TPMS) give us more information.

[greystroke]

10-15 is normal for me.

[Do26]

The recommendation for setting as relaxed ambient is with the engineering knowledge of running increases in temp and pressure... The company engineers and racer engineers (Roger is/was both!) are paid on their knowledge.

Some racers can use bleed off valves, but some can't, so resting ambient is well known and studied.

[cletesingler]

I've seen my GY Marathons increase at least 20 PSI in the TX heat, especially considering concrete vice blacktop road surface. To determine reasonableness I check tire temperatures, and really note that those tires in the sun are always hotter and higher pressures than those on the shady side. In any case, I know that the engineers have calculated this stuff extremely well and I don't think they plan on us deflating for mother nature even in TX. And, if you deflate, where are you going to add pressure when you cool down? Since I'm no where near the weight for 80 PSI, I have more than 10 PSI to "play with" and I usually avoid 100 PSI on my LRE GY Endurances in today's 100 degF. Now a 25 - 35 PSI increase with OEM Chinese tires is another story, remembering well that the increase exceeded allowable limit for my TPMS and I often got the alarm for high pressure........

[Daycruiser]

People worry too much about the tire temperatures, if you set the tire inflation correctly when cold the rest is academic. it's all about the tire pressures staying up when rolling down the road.

[mobilemike]

Originally Posted by road dogs

My 5th wheel tires are 80psi, I always keep them at 75 before a trip for a little expansion headroom.

There is a reason the tire pressures are set COLD.

The engineers have calculated the increase in pressure when running hot.

Set them at the pressure you need for the load and disregard the pressure increase when they get hot. Its part of the equation already.