TT tire pressure increase while on the road

[Springerdad]

I've done a search, but not found the answer I'm looking for, so here goes,,,,, During our last outing, in a new to us TT, I was monitoring tire pressure and temperature, and watched pressures climb to close to 80 psi after 2 hours on the interstate after starting out at a cold 65 psi. I'm guessing TT weight is about 10,000 lbs total, with the tongue at 1000 lbs with the WDH. I have not had a chance to scale it, since that was out first outing,,,,, but the big question is - for those of you with TPMS - what kind of pressures do you see after being on the highway at 60 mph?

[Pod2Vibe]

I see a 6-10 psi increase in cooler temps and 10-14 psi increase in summer, on my TPMS.

My MH is a bit over 11,000# and my Toad is about 2600#

[lbrjet]

Seems a little high to me. I have 7200 lbs on my axles and run 'E' rated tires with 65 lbs pressure. The highest I saw on a 4000 mile trip last summer was 71 lbs. How much did the tire temperature go up? I think about 10 lbs over would be considered 'normal' for summer. Mine run cool I guess.


2010 F250 5.4L 3.73
2011 Flagstaff 831FKBSS
Equal-i-zer 4pt 12K

[Springerdad]

I think it's a bit high too. I'm on ST225/75R15 'D' rated tires, that's what came on it. There's another thread I found where a chart by Goodyear is advising up to 10 PSI above max on sidewall for heavy loads. (not that that increases load capacity or speed ability) I would think that by starting out with 70 PSI in the tires, I could stop a little bit of sidewall flex that's creating the higher carcass temps and resulting pressure increase. Thoughts?

[davel1971]

pressure rises approximately 1 psi for every 10 degrees. Nitrogen is not affected by temperature changes. Might want to consider switching to nitrogen if you want you pressures to remain more constant.

[Springerdad]

Good point. These tires DO have nitrogen in them, or so says the sticker on the TT over them,,,,,,

[youroo]

We have never seen PSI increases like you state! Normal increase around 5 PSI on all 4, slightly more on the Sunshine Side! We run Air in tires! What do you set your Hi Temp and Hi PSI Alert at? Youroo!!

[youroo]

You stated a Chart by Goodyear,but what are your Tires on your Dutchman TT? As you talk about Sidewall flex? Youroo!!

[Springerdad]

Youroo, Westlake is the name on the sidewall, I think. A private label brand as we called them when I was in the auto/tire business. We saw 79 psi on the left side tires, (shade) at 64 mph on the trip up, and 71 psi both sides sun and shade on the trip back at 61 mph.

Sidewall flex - as we look at a radial tire loaded, on the ground, there is a 'squat' to the tire and a slight bulge in the sidewall. As the tire rolls, the sidewall flexes. Naturally, it causes internal friction in the carcass plies, and that creates heat, and the heat increases tire pressure. At some point, the heat causes the tire to dismantle itself. As we learned in Goodyear tire school, tires are 'bonded' together under pressure and heat. Get them too hot, and you can guess the rest.

[youroo]

This is why we Removed the tires that Came on our unit! They were like Bologna Skins, when removed you could WAD them up,replaced with Maxxis! Sidewalls on them are Very Strong! I only reference this in regards to Sidewall Flex,which Builds Heat and makes for a Road Wallering RV! Youroo!!

[D_B Travelers]

We run 65# in Goodyear Marathon ST225/75r15 Load D's and have only seen a 10# rise when running in Nevada, 108 degrees in June. Mostly around 6-8# for normal travel. TT is about 8500# loaded out with 1000# hitch weight. How fast are you running? That may be part of the issue. I usually run right at 65 MPH as that is the speed rating and I am not in a hurry anyway. BUT, you are on the right track and ahead of many RV'ers by having a pressure/temp monitor on your rig.

[Springerdad]

The trip out, we ran at 63 to 64 MPH. After seeing the big rise in pressure I backed down to 60 to 61, and the pressure stabilized and slowly dropped. This was in 60 degree weather. On the return trip, I ran at 61 to 62 MPH and never saw a pressure above 72psi. The temps were in the upper 70s.

[Tom48]

We ran C tires stock at 50 psi Gross is 7350 on 3500lb axles. That was not enough for my comfort. Now we run E tires at 70 psi and on the road they only increase by five degrees over ambient and gain about 5 psi. Maybe running a 10,000 trailer at only 65 psi is too soft and they are heating up more because they are soft.

Aren't D tires usually rated for 65 psi and E tires rated at 80.

[Brother Les]

Check your brakes on the unit. Make sure none are dragging. Take the tires and hubs off and physically look the brakes over. Check your hubs for any drag and wear and look over bearing and regrease. You are begging for a tire failure and it will not be pretty when one goes. Get this looked over before your next long trip.

[Springerdad]

Brother Les - already done. I had all four off the ground after our return and no drag.

Tom - you're correct on pressures for load range

[Springerdad]

FWIW, I went looking on the 'net and found an article that stated a 25% increase in tire pressure can be expected on a fully or nearly fully loaded tire driven at highway speeds....... in my case, 81psi + is acceptable. Huh.

[johntaylor]

Originally Posted by davel1971

Nitrogen is not affected by temperature changes.

Not true. All gases respond identically to temperature changes. It's Gay-Lussac's pressure-temperature law: P1 / T1 = P2 / T2

The only difference with nitrogen is that it is dry. Air contains water vapor. If you start out below the dew point temperature, some of that water vapor will be condensed out. As the tire warms, it will evaporate and increase the pressure, but only very slightly.

For the facts on nitrogen inflation, read this. Now I'll just sit back and wait for the nitrogen police.

[j free]

My 5er on a hot summer day will increase up to 15 degrees on the sun side of the trailer. The non sun side will be as much as 4 degrees less. This is on a hot summer day around California and Arizona. It all depends on what your driving on temps and sun. When you set up the TPMS you input a high warning alarm and My system has that alarm set at 30 degrees over standard temp. I do have Good years on my rig.
By the way my TV tires do the same thing as my 5er.

[MilCop4523]

we are hauling an 09 Sundance 34 foot bunk house. We also run teh Truck Systems Technologies 507 system and start out at 70 lbs on the cold pressure side and it climbs to about 92 to 93 lbs in teh moderate heat.
A bit below 98 degrees in hotter temperatures.
Have driven through a rain shower and watched those numbers drop 15 degrees in less than 5 minutes.
I think you are safe. its the sudden loss and temps above 100 degrees that they say to watch out for

[Springerdad]

Originally Posted by johntaylor

Not true. All gases respond identically to temperature changes. It's Gay-Lussac's pressure-temperature law: P1 / T1 = P2 / T2

The only difference with nitrogen is that it is dry. Air contains water vapor. If you start out below the dew point temperature, some of that water vapor will be condensed out. As the tire warms, it will evaporate and increase the pressure, but only very slightly.

For the facts on nitrogen inflation, read this. Now I'll just sit back and wait for the nitrogen police.

Thanks for that. I was going to refute that myself but decided to keep quiet.