Tire pressures, what to expect

[Tireman9]

Originally Posted by slow

I set my air pressures 5 psi below max when the ambient temperature first thing in the morning at daylight is 15 C (~60F). That is the typical temp for us in the mornings when we set off towing. I am comfortable with the 5 psi below max since a 10 F temp rise brings them up to max. This way I do not have to keep adjusting the air pressure the entire season.

I do not know why so many people thing under inflating their tires is a good idea. Every mile you run underinflated does some additional damage to your structure.


With my recommended +10% you have plenty of room for daily changes without having to mess with your tires. Just NEVER run lower than the MINIMUM inflation based on scale measured load and the info in the tables.


Tires can tolerate a significant increase in pressure. We tire engineers know that and design and test accordingly.

[Tireman9]

Originally Posted by travelin texans

"Cold pressure" is before traveling. Best to check in the morning before traveling. You do not have to check precisely at 68 degrees.

^x2

[Jerry S]

Way too many worry warts here, do as Tireman9 says and forgetaboutit.

[slow]

Originally Posted by Tireman9

I do not know why so many people thing under inflating their tires is a good idea. Every mile you run underinflated does some additional damage to your structure.


With my recommended +10% you have plenty of room for daily changes without having to mess with your tires. Just NEVER run lower than the MINIMUM inflation based on scale measured load and the info in the tables.


Tires can tolerate a significant increase in pressure. We tire engineers know that and design and test accordingly.

So rather than setting 5 psi below max at 15 C, I should set to max at 15 C since that is my typical morning and departure temp.

[jadatis]

I have been calculating again.
Your TMPS measured 108psi/110psi at 50 degrF ambiënt temp, so not driven this means inside tire also 50 degrF. If then you would have read it when ambiënt temp was 65 degrF the second written would be given by TMPS system, probably rounded to 1 psi, most TMPS give it in steps of 1 psi. And 3th is the presure you read when driving so warmer inside tire air.
The about 10% pressure-rising when ambiënt temp is 65 degrF and driving about 50/55mph, comes from an inside tire temp of 110 to115 degr F in tire.


108 psi /50 degrF, 111.6 psi/ 65 degrF, 122psi/109 degrF.

110psi/50 degrF , 113.7 psi/ 65 degrF , 125psi/112 degrF.

Draw your own conclusions, this all I gave on a " nice to know basis"
Realise that I call myself " pigheaded Dutch selfdeclared tirepressure-specialist" , this to point out that I am not a profesional in tires.
For most Dutch and not American, is already a reason to not trust my given information. But the calculation is right asuming no vollume change of tire by the different pressure, wich it practically is for an already pressurised tire.

[notanlines]

Let me throw this wrench into the works. Your TPMS probably does a reasonable job of tire pressures. Sometime take your handy-dandy infrared thermometer and measure the temperature of the wheel and the surface of the tire and see what you get.
It has been said a few times, now once more. Don't overthink this. Air pressure before you leave in the morning and be done with it.

[JRTJH]

When you consider that the temperature sensor in any TPMS "stem system" is going to measure the temperature "at the end of a stalk, 1.5-2.5 inches out in the airstream" and that "stalk" may or may not transfer heat as efficiently as the wheel, rubber tire, air inside that rubber tire might transfer heat, then add in the "cooling effect" of that "temperature sensor" slinging around in the atomosphere, sometimes aided by cooling humidity, sometimes hampered by "scorching sunlight at high noon" and you'll begin to get the idea that temperature "measured by a TPMS valve stem cap" is, at the very best, a close approximation of reality.... Then when you add in all the variables encountered, you can easily come to the conclusion that it may very well not even be a "close approximation"....

TPMS "external sensors" don't do a very good job of "sensing internal tire temperatures".... About the only "close to reality" is to compare both the sensors on the shady side of the trailer and compare both the sensors on the sunny side of the trailer. If each "pair is somewhat close" then that's about as "much temperature reality as you'll get" from a "stem cap TPMS" readout.

Think of it this way: Aim the red dot from an infra-red thermometer at a mirror, bounce the reflection off the mirror toward the tire and judge whether you're close or not to reading the area of the tire where you're concerned with temperature.... Your TPMS may (or may not) be as accurate as the reflected red dot reading.....

[jadatis]

Infrared-thermometers only give temp of the outside ,and the place you aim them on.
So are also not reliable.
Best you can get is remember the cold pressure and ambiënt temp at the moment of cold measurement, then calculate from the difference in pressure, the temperature in tire.

Some tmps systems with internal sensors, compensate the pressure back to fi 65 degr F.
Only with internal sensors this can be done, because those send pretty exact the temp in tire , to the little computer.

[JRTJH]

Originally Posted by jadatis

Infrared-thermometers only give temp of the outside ,and the place you aim them on.
So are also not reliable.
Best you can get is remember the cold pressure and ambiënt temp at the moment of cold measurement, then calculate from the difference in pressure, the temperature in tire.

Some tmps systems with internal sensors, compensate the pressure back to fi 65 degr F.
Only with internal sensors this can be done, because those send pretty exact the temp in tire , to the little computer.

There are (AFAIK) no "market available TPMS systems with internal sensors available for travel trailer use.

[+Ruff Rider]

I check my tire pressures before I leave on my trip. That is the last time I check tire pressures for the entire trip. I do however look at them to make sure I don't have a low tire. Checking air pressures lets air out every time. I dont believe in TPMS. To much stuff in the truck already. How many times do you check your truck tires? I can't remember the last time I checked them.

[tech740]

Originally Posted by +Ruff Rider

I check my tire pressures before I leave on my trip. That is the last time I check tire pressures for the entire trip. I do however look at them to make sure I don't have a low tire. Checking air pressures lets air out every time. I dont believe in TPMS. To much stuff in the truck already. How many times do you check your truck tires? I can't remember the last time I checked them.

I check mine with the TPMS before and during every trip, both the camper and the truck.

[JRTJH]

Originally Posted by +Ruff Rider

I check my tire pressures before I leave on my trip. That is the last time I check tire pressures for the entire trip. I do however look at them to make sure I don't have a low tire. Checking air pressures lets air out every time. I dont believe in TPMS. To much stuff in the truck already. How many times do you check your truck tires? I can't remember the last time I checked them.

I check tire pressure EVERY morning before towing. If we are staying in a location for 2 weeks, I do not check tire pressure until the day of departure, but tires "don't roll without a current pressure check"..... That's truck tires, trailer tires and if we're double towing, the tires on the boat or motorcycle trailer as well. Additionally, at EVERY stop, as the truck is "cooling down by idling" I walk around the truck/trailers and use an infra-red thermometer to check temperature on every tire. I'm looking for a "large variance in temperature" not a "subtle 1 or 2 degree difference. If I notice a marked increase in temperature at one wheel location, I don't move the rig until I've determined the cause.

I also check lug nut torque the first day of each trip. I do not check lug torque during the trip unless there is a reason to retorque (change of tire, flat tire, etc)…..

[flybouy]

Wow, lot's of opinions on this. I know NASCAR drivers will have a 1/2 lb psi added/subtracted when track Temps rise or fall. I'm not driving my camper making constant left turns at 200+ mph so here's what I do.

I check truck and trailer tire pressures before a trip. Set pressure with a good gauges known to be accurate. Trailer get's set to max cold 80 psi. No adjustment on that unless it's below about 40f. The TPMS will let me know if there is a problem (the air and temp min/max is adjustable in the trailer TPMS).

As John does, when I stop I let the truck idle down so the turbo spools down and cools off. That's when the the dog and I take a walk. Leash in one hand, inferred thermometer in the other. My main concern are hub Temps but I do shoot the brake drum and the tire. On the way back I'll shoot the ball coupler as well. It's not like it costs money or takes a lot of time. If it's very hot, 90 deg f or above with blacktop Temps approaching 140+ in the sun I'll bend down and "shoot" the rear diff.
This has worked well for me. YMMV

[CrazyCain]

Originally Posted by JRTJH

I check tire pressure EVERY morning before towing. If we are staying in a location for 2 weeks, I do not check tire pressure until the day of departure, but tires "don't roll without a current pressure check"..... That's truck tires, trailer tires and if we're double towing, the tires on the boat or motorcycle trailer as well. Additionally, at EVERY stop, as the truck is "cooling down by idling" I walk around the truck/trailers and use an infra-red thermometer to check temperature on every tire. I'm looking for a "large variance in temperature" not a "subtle 1 or 2 degree difference. If I notice a marked increase in temperature at one wheel location, I don't move the rig until I've determined the cause.

I also check lug nut torque the first day of each trip. I do not check lug torque during the trip unless there is a reason to retorque (change of tire, flat tire, etc)…..

Spot on!!

[RVPP]

Originally Posted by 66joej

I believe the manual says set tire pressures when cold. Could be 0F or +70F. YMMV

Back in high school science class I recall "STP". Standard temperature and pressure. Standard temp. was 70degs. F. at sea level. How if you're in Denver the air pressure in WAY different than say Miami not to mention the temp. So all of you nice folks can figure out what 'cold' is. Me, I stay near sea level and I prefer warm temps. Happy trails folks.

[CWtheMan]

This is how NHTSA describes proper tire inflation pressures for OE tires.

"The vehicle manufacturer's recommended tire inflation pressure is the proper psi when a tire is cold, meaning it has not been driven on for at least three hours. To get an accurate tire pressure reading, you must measure tire pressure when the tires are cold."

When someone reads more into what's there, it's their opinion.

[chunker]

It's amazing to read all these posts where some start talking about "their method" referring to weights of the RV, PSI for tires etc. Since I suspect 90+% of RV owners can't spell CAT scales, know where to find them, or how to use them. I suspect some people don't trust or use a TPMS because #1 they don't understand it, #2 they are too cheap to buy one, #3 they operate in a "what I don't know can't hurt me" mode. Then there's of course the trolls who just make up crap and post on forums to stir the pot.

For the most part you are free to operate as recklessly as you wish just don't take out other innocent people in the process. I won't cite examples because some wouldn't understand anyway. Me, I'll continue to utilize my TPMS, know my weights based on scale tickets, adjust speed and load for the conditions, and try use the best available equipment. If I stepped on someones toes here I'm really sorry you stuck your toes out so far.

[+Ruff Rider]

You know why people need a DRW truck?
Its because they think they need to carry so much crap in there truck. What did RVers do before all this TPMS, Cameras Navigation systems. We had fun camping and going places. Now some RVers think they need all this crap to be safe. It's utter nonsense.
Checking air pressures every day, honey get the inferred temp thingy LOL, I have my back up camera on all the time because I have to see some guy behind you.
Camping for some folks is more work than its worth. If I had to worry as much as some folks do I would just stay home.
Only reason you have to add air to your tires is because you let to much air out checking. All these charts and stickers numbers Cat Scales trips. Its all a bunch of crap. You just don't need to worry all the time. Just stay home and be safe.

[Roscommon48]

assuming you have 'g' rated tires so the increase in normal and the tires are built with the increase in mind. as stated above don't over think it.


if you are concerned talk to a tire company.

[CWtheMan]

Inflating our trailer and tow vehicle tires to the load carried is not the accepted or recommended method. That particular method is from the Federal Motor Carrier Safety Administration (FMCSA) – trucking industry – and is not applicable with the Federal Motor Vehicle Safety Standards (FMVSS) that apply to our trailers and tow vehicles.

A common misunderstanding about our tires is the recommended inflation pressures depicted on the vehicle certification label and in the vehicle owner’s manual. Those recommendations are correct for that vehicle as manufactured and will remain correct unless the GVWR is modified.

Tire industry standards tell us how to keep those recommendations correct. Here’s how. Replacement tires are required to provide, at the very minimum, an amount of load capacity equal to what the Original Equipment (OE) tires provided via tire inflation. NHTSA allows the use of auxiliary placards for providing the recommended inflation pressures for the replacement tires should they be different from the OE tire pressures. All of us have the option to use increased inflation pressures between what has been recommended and what is shown as maximum on the tire sidewall. Brand names don’t make a difference; that’s why they are never mentioned in the regulations.

When I don’t use the acronym IMO in my posts it means I have not knowingly strayed from the regulations and standards messages.