TPMS: Too much info... how hot is too hot?

[jimmarako]

My current trailer came with the internal TST TPMS system. I really like it, but was wonder how hot is going to be too hot?

On our Memorial day trip both travel days turned out to be overcast with temps in the low 70's. During the 3 hour drive I notice all 4 trailer tires stayed fairly close in temp and PSI. The temps went up to low 100's while the PSI increased 5-6 PSI. This is a 30 degree temperature rise on a cloudy day.

In a few weeks we are taking a trip to Georgia heading down I81 -> I77 -> I85. Being July I can easily see the temps down south pushing 95+ degrees. If its sunny the road temps will be what.. 10-15 degrees higher? The tires on the sunny side will also be 10-15 degrees hotter.

Doing the math I get 95 + 10 +10 +30 = 145 degrees minimum for the sunny tires if everything I assumed holds true. This seems kinda hot to me.

Those of you that run TPMS on hot days what are you seeing temp wise? Am I way off base here? Or if 140, 150, 160,... normal expected temps?

Thanks
Jim M.

[Rockinh]

There is a pretty good article on this in the link. It will also tell you that the tire pressure monitors will only tell you the air temperature inside the rim and not the tread temperature, and the difference will be significant. Most Tpms will list 158 as a critical temperature to not exceed. The critical temperature for the tread is over 200 (around 220). I am not sure if those 2 measurments equate, just understand that you can set the temperature alarm in your monitor but the default will be around 158-160. A 50 degree rise is going to be normal and perhaps even low on a 95 degree day. You can help that by keeping your cold tire pressure up towards the high. I like to keep mine 10 under max. Check out this link.

https://www.rvtravel.com/is-there-a-...e-temperature/

[The Evil Twin]

Dead of summer I have seen as high as 150. There is sometimes a 10* difference in the tires. When it is above 95 outside I inflate to the max pressure to keep the tires cooler.

[Chuck_S]

Run ST (special trailer) tires at the maximum temperature listed on the sidewall. No need to run them softer, no one is riding inside.

-- Chuck

[The Evil Twin]

^^what he said
I meant to type “above”. That recommendation came from a Goodyear doc posted on this site.

[Chuck_S]

And I, of course, meant to type pressure, not temperature.

-- Chuck

[jimmarako]

Thanks for the replies. I have ST 225/75R15 load range D tires I keep near 65psi, so thats covered. Ignorance is bliss. Before TPMS and long as the tires (on cars/trucks) didn't look low all was good. Now seeing how high the temps get Uhg.

Next weekend we have a short ~2 hour trip. If its warm and sunny out I'll get another data point to think about.

Jim M.

[SlowrideHD]

First thing I would do is go up to a load range "E" and run 75 psi.

I run load range "G" on my camper at 105 psi cold. Better fuel mileage and my tires will probably outlast the camper.

[The Evil Twin]

Originally Posted by Chuck_S

And I, of course, meant to type pressure, not temperature.

-- Chuck

What day is it? Who knows....who cares...

[Tom48]

Our TH came with load range D tires which NEEDED TO START DAY COLD AT 65 psi. Set my LR-E tires Cold, to 75, 5 below their max. Never a problem And on both the sunny side of coach ran hotter and couple pounds higher than the shade side. Left high temp warning on our TST TPMS at factory default and set low pressure warning at 70. Saved our bacon couple times but never saw enough temp rise to concern me.

[TowPro]

my in-law is a warranty manager for a very large tire manufacture (for almost 30 years now).

I asked him that very question when I saw him last weekend.


He said at 170 deg I would start to be concerned and maybe slow down. at that point also check the PSI and load you have on the tire.


He said 170 deg the tire can start to get softer and war faster. He said race car tires start to push 200 deg F but they are designed to stick better when hot (and soft)

[CedarCreekWoody]

Probably the thing to really watch for is one tire running much hotter than the others or one that is heating up faster than others. This could signify a developing problem and would warrant stopping to check it.

[DouglasReid]

Another consideration is your speed.

Most ST tires are rated at 65 MPH. Driving faster heats them and can be dangerous.

[AlaskaErik]

Originally Posted by DouglasReid

Another consideration is your speed.

Most ST tires are rated at 65 MPH. Driving faster heats them and can be dangerous.

That's an old wives tale. I've never seen tires rated that low, although they probably exist. My Goodyear Endurance tires are speed rated to 87 mph, which is faster than I'll ever pull either of my trailers.

[DouglasReid]

Originally Posted by AlaskaErik

That's an old wives tale.

One of the best around, Maxxis 8008s, are so labeled on the sidewall.

Think and do as you choose..................Good Luck!

[AlaskaErik]

Originally Posted by DouglasReid

One of the best around, Maxxis 8008s, are so labeled on the sidewall.

Think and do as you choose..................Good Luck!

There seems to be some controversy about the Q rating of those tires. Maxxis, on their web site, labels these tires as high speed. I'll let others debate that one. My Goodyear Endurance tires are officially designated as being speed rated to 87 mph and I've towed my KZ at speeds up 80 mph.

[DouglasReid]

Originally Posted by AlaskaErik

There seems to be some controversy about the Q rating of those tires. Maxxis, on their web site, labels these tires as high speed. I'll let others debate that one. My Goodyear Endurance tires are officially designated as being speed rated to 87 mph and I've towed my KZ at speeds up 80 mph.

There isn't really any "controversy".

I had a set of 4. they were clearly labeled as a Maximum Speed of 65 MPH!

[jimmarako]

I wasn't going to say much but then I realized its my thread so why not

About the Maxxis tires. Looking into this I found a thread from 2 years ago discussing the "confusion" over the speed rating. The company does clearly suggest/say/mention that the tires are Q rated (which is 100MPH). But then their lawyers must have gotten involved because they mention 2 or 3 "tire agencies" that only allow trailer tires to be rated at 65MPH no matter who makes them. Then there was a discussion of the "tire data book" that limits trailers to 75MPH.

So it is very confusing.

I don't work with or near tires so I have no knowledge beyond what a typical weekend warrior would have. I agree with those that say what is stamped on the tire is what counts. Not whats on a website or is some data book.

If your Maxxis tires say 65 max, then I would believe that. My Castle rock tires say something like "Speed rated to 75MPH max "L"". If your Goodyears are stamped with an "N" then 87 it is.

This is like Deja Vu all over again. About 20 years ago I bought my first horse trailer and found some "trailer" Forum site. At the time the speed limit had only been 65 for several years. Many people were stating that trailer tires can't go over 55Mph and that you would be crazy to drive a trailer over 55 anyway. Today speed limits exceed 70 in many places so now people complain about going over 65 with a trailer.

Jim M.

[Tireman9]

Originally Posted by Rockinh

There is a pretty good article on this in the link. It will also tell you that the tire pressure monitors will only tell you the air temperature inside the rim and not the tread temperature, and the difference will be significant. Most Tpms will list 158 as a critical temperature to not exceed. The critical temperature for the tread is over 200 (around 220). I am not sure if those 2 measurments equate, just understand that you can set the temperature alarm in your monitor but the default will be around 158-160. A 50 degree rise is going to be normal and perhaps even low on a 95 degree day. You can help that by keeping your cold tire pressure up towards the high. I like to keep mine 10 under max. Check out this link.

https://www.rvtravel.com/is-there-a-...e-temperature/

Yup that was my blog post.


Yup most TPMS come with the max temperature set to 158F which is a good warning temp.


If you have ST tires and have not gone bigger in size or up in Load Range you should be running the pressure on the sidewall. I have a number of posts on ST tires and why you should run that pressure.
You should also review your RV owner's manual as you will see that in most cases they advise you to run the pressure shown on the RV Certification label (located on driver side, outside, toward the front) of your trailer.

[Tireman9]

Originally Posted by Tom48

Our TH came with load range D tires which NEEDED TO START DAY COLD AT 65 psi. Set my LR-E tires Cold, to 75, 5 below their max. Never a problem And on both the sunny side of coach ran hotter and couple pounds higher than the shade side. Left high temp warning on our TST TPMS at factory default and set low pressure warning at 70. Saved our bacon couple times but never saw enough temp rise to concern me.

You should not run lower pressure and count on the pressure rise when hot. The cold pressure is the only pressure we are concerned with and if properly set you should not have to worry about the hot pressure as we tire design engineers make allowances for normal temperature rise.