Tire Pressures and Tire Temperature

[CapriRacer]

Originally Posted by ckottum

CapriRacer, does this mean that if we run our Michelin 16" LTX tires on our Airstream at 60 psi, rather than the 80 psi maximum pressure indicated on the sidewall, that is a correct pressure if it passes your pressure test procedure?

That seems to be in conflict with another tire engineer who has recently cautioned here that any tire used on a multi-axle travel trailer with lowered pressure is more likely to experience tread separation from sideway scrubbing when turning the trailer, so we should always use the maximum sidewall indicated pressure.

Or are you suggesting we should always use the maximum sidewall indicated pressure, and then use your pressure test procedure to ensure it is enough? I suppose the two tire engineers would be in agreement then?

The correct tire pressure for our Airstream remains unclear to me.

cheryl

Cheryl,

I think Roger and I are on the same page. RARELY, will the final answer be significantly less than the maximum.

At the same time, I am recognizing that it is POSSIBLE that all the charts and calculations result in something LESS than the maximum and the test is a way to confirm.

I can understand why the correct pressure is unclear. What should have happened, didn't. That's why we are going through all this - to do what should have been done so that it is transparent to the end user.

[Msmoto]

This has been very helpful, and I will do the cold/hot inflation test next week. As I carry a compressor in the back of my truck, I can make adjustments at anytime by simply starting up the generator also in the truck bed.

Thanks much for all the help.

[Msmoto]

Update: after hundreds of miles pulling, temps in the 90's, all my tires/wheels were only warm to touch, not hot in any way. Suggests I must be close with the pressures. However, with my extra fuel onboard in the bed of the truck, I went across the scales and read: Front axle 4490 lbs, rear 4920 lbs, trailer 7280 lbs.

Current pressures are F/R on truck 60 psi, trailer 65 psi, and I believe I will increase the rear tires on the truck to 65 psi due to the slightly bigger load with the extra 475 lbs of fuel in the bed.

Oh, yes, subtracting the 475 from the 4920 shows 4445, or nearly perfect front/ rear balance without extra fuel, which suggests to me the hitch must be set up about right at present.

Also, sure is nice to go a thousand miles without having to add fuel ....LOL


Ms Tommie Lauer
Greensboro, NC
2015 Serenity 30 RB / 2008 Dodge Cummins 4 X 4
WBCCI #4165 AIR #31871

[overlander63]

Originally Posted by Msmoto

Also, sure is nice to go a thousand miles without having to add fuel ....LOL

Of course, when it finally is time to refuel, your credit card starts whimpering...

[Tireman9]

Originally Posted by Msmoto

Having just installed new 16" wheels on my 2015 Serenity, along with the Firestone Transforce LT225/75R16, I am attempting to decide on the correct tire pressure and how to determine this.

In ambient temperatures of 80º F, at no time was the tire more than warm. Even with 30 - 40 mph sideways gusts of wind over several hundred miles, the tires and wheels remained only warm to my hand, never hot enough to prevent touching.

My question is, can one determine the correct tire pressure based upon how arm the tire gets in use? It would seem to me, if the tire were under inflated, it would become much warmer, way to hot to touch. Correct inflation would result in the coolest running temperature.

Mine are at 65 PSI currently and I am thinking this is the correct pressure, but would like the experience of others with 16" wheels/tires.

No using tire temperature is NOT the correct way to determin inflation pressure.

Motorhomes and TV are different then trailers.

All vehicles
1. learn the actual load on each tire position. Link to work sheet available on this web page. If you can't do that then at least learn the actual load on each axle when the vehicle is fully loaded.

2. Consult the tire load & inflation tables to learn the MINIMUM pressure each tire needs to carry the load. If you don't learn the individual position load then assume some side to side unbalance on each axle as almost none are 50/50. Some are off as much as 45/55. As a minimum I would suggest that one side carries 53% of the axle load. Use that load to learn the MINIMUM cold inflation.

3. All tires on an axle should have the same inflation i.e. you will be inflating to the pressure needed by the heavier loaded side.

4. Give yourself some margin so you don't have to add air every time the temperature drops. Remember 10F means about 2% pressure change.
I suggest a 10 % margin over the minimum. This way you should be able to go weeks or even month before you need to add air.

5. Run a TPMS so you get a warning of a slow leak so to avoid a Run Low Flex Failure or "Blowout"

6. Trailer exception. You still need to confirm you have enough pressure to carry the load BUT if you have a multi axle trailer you have a special situation. Whenever turning a corner or rounding a curve there are internal structural forces trying to tear the tread and belts off the tires. This is called "Interply Shear" Google the term if you want to learn more. The best thing to do if you have a multi axle trailer is to run the inflation molded on the tire sidewall. This will lower the extra shear forces.

[Msmoto]

Trailer weighs 7280 lbs. each axle carries about half, or 3640 lbs. if one wheel has 55%, this would be about 2000 lbs. per the chart, 60 psi would be correct....ironically, this is what the folks at the tire store used. But, at a 10% additional margin, 65 psi is close......and this is what I am using.

The trailer is stored in a garage, tire pressures are checked before each trip, and temp in the garage is about 80 degrees F. Pressures had dropped about a pound since last trip a month ago.

I am fairly precise about these things and decided on 65 psi based on the recommendations of AS, plus adding my 10% to the tire dealer's original pressure.

Actually, using a very accurate infrared temperature gauge which can see temp differences across the tire face is quite useful in determine how the tire is going down the road. This same technique is used for race cars for chassis set up.


Ms Tommie Lauer
Greensboro, NC
2015 Serenity 30 RB / 2008 Dodge Cummins 4 X 4
WBCCI #4165 AIR #31871

[Tireman9]

Temperature guns are good for checking heat conductive materials such as your wheels or brake drums & hubs but there can be 40F to 60F variation in areas only 1/2 to 1/4" apart on a tire as rubber is an insulator as seen in my blog post of may 15 2012 thermographic picture.

[blufishin]

I recently installed a TPMS on my new 25FC that provides tire temp as well as pressure. Went for a test run yesterday in the interstate and observed tire temps ranging between 91 and 110 with the higher temps on the front axle. Outside temp was 85 degrees. Max speed 65. GYM tire pressure approx 65psi. Can anyone tell me what the typical tire temp is under these circumstances? Why the higher temps on the front tires? And how reliable is the data from a TPMS? Thanks, Jere

[SteveSueMac]

Originally Posted by blufishin

I recently installed a TPMS on my new 25FC that provides tire temp as well as pressure. Went for a test run yesterday in the interstate and observed tire temps ranging between 91 and 110 with the higher temps on the front axle. Outside temp was 85 degrees. Max speed 65. GYM tire pressure approx 65psi. Can anyone tell me what the typical tire temp is under these circumstances? Why the higher temps on the front tires? And how reliable is the data from a TPMS? Thanks, Jere

Hi - see posts 26 and 49 in this thread.

I also started another tread to ask what you should expect to see and got the answer that up to a 10% rise in pressure and 30 degree increase above ambient temperature for highway driving is expected (a preference of 5-10% pressure rise and if above 15%, do something very different - again, see the 2 posts referenced above).

Your fronts may be hotter because you've loaded them with more weight either because you have more weight sitting on or in front of your front axle or because your trailer isn't level (I'm guessing nose down?) which would put more load on the front axle. It could also be sticking brakes.

Any of those conditions on your setup could be the problem. It's also possible (not likely) the 2 TPMS sensors in the front happen to register higher than the 2 in the rear.

[Tireman9]

Originally Posted by Msmoto

Update: after hundreds of miles pulling, temps in the 90's, all my tires/wheels were only warm to touch, not hot in any way. Suggests I must be close with the pressures. However, with my extra fuel onboard in the bed of the truck, I went across the scales and read: Front axle 4490 lbs, rear 4920 lbs, trailer 7280 lbs.

Current pressures are F/R on truck 60 psi, trailer 65 psi, and I believe I will increase the rear tires on the truck to 65 psi due to the slightly bigger load with the extra 475 lbs of fuel in the bed.

Oh, yes, subtracting the 475 from the 4920 shows 4445, or nearly perfect front/ rear balance without extra fuel, which suggests to me the hitch must be set up about right at present.

Also, sure is nice to go a thousand miles without having to add fuel ....LOL


Ms Tommie Lauer
Greensboro, NC
2015 Serenity 30 RB / 2008 Dodge Cummins 4 X 4
WBCCI #4165 AIR #31871

A quick trip across a truck scale to learn the actual load on eaxh axle of both the TV and each axle on the TT will give you ne numbers you need to learn the MINIMUM Cold Inflation Pressure needed.
A bump of 10% on the TV is certainly reasonable.

Multi axle TT are a different matter.
The ir CIP should be the tire sidewall pressure (unless you have gone over size or up a Load Range or two).
It is the Interply Shear force (Google: Tire Interply Shear for the background) that can contribute or even cause a Tread & Belt Separation.