Important info on tire pressure increase—Don’t believe everything you read

[MoonShadow_1911]

Reposted from rvtravel.com

https://www.rvtravel.com/important-i...read-rvt-1100/

The topic of tire pressure seems to never die.

I just ran across a post from an enthusiast in Europe who has the “hobby”(??) of worrying about tire temperature and pressure.

He started out a few years ago by developing his own Load and Pressure formula, which is fine if that is what he finds interesting. But he then published the results of this new equation.

Now, if someone wants to play around with the established worldwide tire industry standards, that is up to them. The problem I have is that it is hard enough to educate RV owners on the importance of using the established tables. We do not need to add confusion from an individual, no matter how well intended, who is not a tire engineer. Even with my 40+ years of experience in tire design and testing on tires used on trucks, passenger cars, and Indy cars, I rely on the industry-published standards tables like this:



I also confirm with similar standards from Europe and Japan when necessary.



Yes, there are companies and people that do not understand tires and they think there is some “magic” temperature, when the major tire companies ALL agree with TRA, ETRTO and JATMA (in picture above) that ambient is the only correct reference temperature.

In the U.S. there is a very large tire retailer, Tire Rack, that focuses on high-performance tires but also sells regular tires. For years they said that pressure increases by 1% for each rise of temperature of 10° F. After I contacted them a few years ago and sent them a link to my RVTireSafety.net blog, they corrected their information to the much more accurate 2% for each 10° F.

There is a relationship between tire temperature and pressure

While there definitely is a relationship between tire temperature and pressure, most people have been led to believe that their TPMS is reporting the temperature of their tire. This is just misleading information. The problem with being concerned with tire temperature readings from TPMS is that the temperature reported by TPMS is actually the temperature of the metal wheel which is conducting heat from the metal hub and brakes. If a TPMS warns of high temperature, it usually means there is a mechanical problem with wheel bearings or brakes.

If there were a problem with an increase in the temperature of the tire structure it would show up with an increase in pressure long before there would be a meaningful increase in the temperature reading.

RE tire pressure increase: If the cold pressure has been set correctly, i.e., based on measured tire loading, and the cold pressure is set to no lower than the pressure for that load in the tables, there should not be a pressure increase of more than about 20% unless you are speeding, i.e., higher than 65 to 75 mph for tires in RV usage. I have found that if people run 10% more than the minimum pressure specified in the tables for their measured load, they will only see the pressure rise of 10 to 15%. Not everyone can run that +10% pressure because they would exceed the max wheel psi. These folks will need to reduce their tire loads.

Roger Marble

Check out my Blog www.RVTireSafety.Net

[MoonShadow_1911]

I posted this because it gives good information on tire pressures and TPMS temperature readings.

The gist of the article is your initial tire pressure should be based on the ambient temperature before driving, that tire pressure increases 2% for every 10° F of temperature change, and temperature monitoring isn't monitoring the tire, but the temperature of the rim, which is probably coming from the hub and brakes.

[Hoopy Frood]

Always good reading, but not too sure I agree with his comments about TPMS temperature readings are not representative of tire temperatures. I agree that the TPMS sensor is most likely showing wheel temperature, but isn't the wheel temperature going to be very close to tire temperature? They aren't really independent of one another.

[xrated]

I think I'll stay out of this topic of discussion, my old brain just ain't in the mood for any deep thought today! LOL!

[Scott'n'Wendy]

Hmmmm. Went from the freezing Northern Ontario temps to the sunny Phoenix temps. I left in morning with the tires set to 80psi Ambient. On the way south I bled some air. On the way north later in the spring I added air. Seems simple to me. Tires stayed together for the trip.

Everybody needs to have a hobby I guess. Mine is shooting and scale models...lol....not tire pressures

[ajg617]

I reset the TV and RV tires at least a dozen times on two trips last year - always in the morning before the sun hits one side or the other. We started out with night temps in the mid 30s upstate NY and hit 106 in Wyoming. Heading across South Dakota, my TPMS PSI alarm went off at 145. Dropped 10mph and stopped at the next stop to let a 5psi out. According to Cooper, max pressure is +20% which would be 150 and max Temp is 180 - yikes we topped out at 108.

[jleonard]

We were on a 4 month trip last summer from Florida, out west to Wyoming, then east to CT then back to Florida. I only added air once to one tire, and that was only a couple of PSI.
Checked pressures before we went to the GD Florida rally last week and the pressures were perfect.
I now have Goodyear Endurance tires.
When I had the Westlakes, they needed air constantly.
I hate to jump to a conclusion based on only one sample, however........

[AZMike]

We were on a 4 month trip last summer from Florida, out west to Wyoming, then east to CT then back to Florida. I only added air once to one tire, and that was only a couple of PSI.
Checked pressures before we went to the GD Florida rally last week and the pressures were perfect.
I now have Goodyear Endurance tires.
When I had the Westlakes, they needed air constantly.
I hate to jump to a conclusion based on only one sample, however........

My experience with the Westlakes was similar to yours. I had to add air far too often (in my opinion). I rarely have to add air to my Endurance tires since I got them two years ago.

[Scott'n'Wendy]

Does mention about wheel pressure rating. A lot of people don't realize the wheels have a pressure rating too. My previous trailer had wheels that had "MAX 65PSI" cast into the backside of one of the spokes. I'm thinking that is a cold pressure as well but don't know for sure. I ran 80psi tires on those wheels at 80psi cold for a few years....