Tire Pressure and Temp

[rjackson]

[QUOTE=JFlightRisk;1083793]Your tire pressure will drop about one pound for every 10* the temperature drops, and another one to three pounds of loss per month. Tires are porous, just the nature of the rubber.

if your tires lose 1 to 3 lbs a month you have other problems

[Bill Johnson]

Originally Posted by foglght

The tires heat up pretty quickly even in colder temperatures. There is no reason to run them more than 80 hot (with the stock tire saying 80psi cold max).

Rear axle GVWR is 9500lbs and the dually tires (per side) are I believe rated at 4940 (depending on tire) so the total is 9,880lbs which is more than the rear axle should take anyway which would be at the 80PSI.

The charts are for the most part linear from 40-80psi so somewhere between 75-80 psi hot is all one would need.

Same with the front. Its rated at 5k lbs. The tires @ 80psi are rated for 5,360lbs.

If your rig is over GVWR that's a different problem.....

I typically run the tires at 70 cold. Never had an issue. They ride nicer as well.

A lot off topic, Just wondering if you ever got the shake fixed on the motorhome

[JFlightRisk]

[QUOTE=rjackson;1084339]

Originally Posted by JFlightRisk

Your tire pressure will drop about one pound for every 10* the temperature drops, and another one to three pounds of loss per month. Tires are porous, just the nature of the rubber.

if your tires lose 1 to 3 lbs a month you have other problems

I've found the monthly pressure drops depends on the brand and quality of the tire. The DW bought a car with brand x tires on it, and I had a heck of a time keeping air in them. I suspected bead leaks, strange to have it happen to all four, but possible, so I had a local tire shop break them down, clean the beads and seal them. Same problem. I took one off, put it in a vat of water, and you could see the bubbles form very slowly on the side walls. Bought a new set of top-of-the-line tires, and the problem went away. I don't buy that brand anymore.

[foglght]

Originally Posted by Bill Johnson

A lot off topic, Just wondering if you ever got the shake fixed on the motorhome

Well that is off topic.

Never did get it "fixed."

After all said and done, I believe it is a frame shake issue with either poor build or lack of engineering.

If I fill the fresh water tank and put my bike rack with bikes on it, it drives perfectly fine. If I'm completely unloaded and getting low on fuel, the shake re-appears. So the last 3-4 times I drive to the racetrack, I just make sure I fill the fresh water tank and put my ebike on the back.

I considered taking the hellwig springs out or softening them to see if it was a driveshaft alignment and ride height issue. Haven't had time for that yet.

Still has the problem when flat towing the jeep, though I haven't tried to put a full fresh water tank while flat towing yet. I've given up on taking it anywhere.

[Bill Johnson]

Originally Posted by foglght

Well that is off topic.

Never did get it "fixed."

After all said and done, I believe it is a frame shake issue with either poor build or lack of engineering.

If I fill the fresh water tank and put my bike rack with bikes on it, it drives perfectly fine. If I'm completely unloaded and getting low on fuel, the shake re-appears. So the last 3-4 times I drive to the racetrack, I just make sure I fill the fresh water tank and put my ebike on the back.

I considered taking the hellwig springs out or softening them to see if it was a driveshaft alignment and ride height issue. Haven't had time for that yet.

Still has the problem when flat towing the jeep, though I haven't tried to put a full fresh water tank while flat towing yet. I've given up on taking it anywhere.

Thanks, I came across the old thread and just wondered what it might be

[Tireman9]

Originally Posted by JFlightRisk

Your tire pressure will drop about one pound for every 10* the temperature drops, and another one to three pounds of loss per month. Tires are porous, just the nature of the rubber.

The added cargo in the bunks will have an effect, as will the sun shining on that side when you're traveling. If you set them to the max pressure, they have a built-in tolerance for the higher pressure when they're warm. They're engineered to take it, so no one has to continuously adjust for warm or cold tires as you drive.

Actual change is about 2% for each 10 F. The 1 psi for 10F is ok for passenger tires running 36 psi but not RVs running 65 to 80 or higher.

[Tireman9]

Originally Posted by JFlightRisk

Your tire pressure will drop about one pound for every 10* the temperature drops, and another one to three pounds of loss per month. Tires are porous, just the nature of the rubber.

The added cargo in the bunks will have an effect, as will the sun shining on that side when you're traveling. If you set them to the max pressure, they have a built-in tolerance for the higher pressure when they're warm. They're engineered to take it, so no one has to continuously adjust for warm or cold tires as you drive.

Sorry got logged out...


RE tire pressure variation. TPMS are not accurate pressure gauges. They are intended to warn about a pressure change.

[RoyB]

Don't know about a class C but my class A will run a few degrees hotter in the downwind tires in a crosswind. I assume this is caused by the added weight of the wind pushing sideways on the side of the barn.

[pconroy]

Originally Posted by Tireman9

Sorry got logged out...


RE tire pressure variation. TPMS are not accurate pressure gauges. They are intended to warn about a pressure change.

This is absolutely worth repeating. For the money I paid - I know my pressure and temperature values are NOT "NIST Certified" values. They're "good enough" for me to watch for big swings.

I've been pleased that the temperatures seem to be +/- 5*F of reality. The pressures are also within 3-5 lbs of "other gauges".

When the TPMS says "75 psi" I know it's "around 75, plus or minus a few pounds".

[Tireman9]

Originally Posted by RoyB

Don't know about a class C but my class A will run a few degrees hotter in the downwind tires in a crosswind. I assume this is caused by the added weight of the wind pushing sideways on the side of the barn.

Yes. Downwind tires will have more load which gives increased temperature.