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Tire Pressure Calculation
Disclaimer is that I have done what I think is extensive research regarding the subject and I think I have an idea of what needs to be done.

I am running Firestone Transforce HT, 8.75R16.5LT 115/111R on all 6 tires. My GVWR is 10,500 thousand pounds. My understanding is that each axle needs to be divided by the amount of tires present. I also understand that weighing the vehicle is the best route to determine tire pressure per axle. Given all this, please share any thoughts that will ensure I go about this correctly so to achieve correct pressure. TIA.
LD 22', 1989 Custom Build. Chassis 1990 Chevy Van G30, 5.7l.
Re: Tire Pressure Calculation
Reply #1 –
Did you read "All About Tires," in The Lazy Daze Companion? I believe it contains the information you need.
Sam
 
Re: Tire Pressure Calculation
Reply #2 –
The LD Owner's Manual also has the needed inflation information and a tire pressure/weight chart. The duals have different recommended pressures than the front tires.
Use LD's chart or the tire manufacturer's pressure chart for your tires.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Tire Pressure Calculation
Reply #4 –
Quote from: Mindispower  - 
Disclaimer is that I have done what I think is extensive research regarding the subject and I think I have an idea of what needs to be done.

I am running Firestone Transforce HT, 8.75R16.5LT 115/111R on all 6 tires. My GVWR is 10,500 thousand pounds. My understanding is that each axle needs to be divided by the amount of tires present. I also understand that weighing the vehicle is the best route to determine tire pressure per axle. Given all this, please share any thoughts that will ensure I go about this correctly so to achieve correct pressure. TIA.

This chart might be helpful...  Firestone Transforce HT Tire Pressure Chart
Cheryl (a.k.a. Desert Diva)
1998 Lazy Daze (26.5 mid-bath)
2002 Honda CR-V
Re: Tire Pressure Calculation
Reply #5 –
Quote from: Larry W  - 
The LD Owner's Manual also has the needed inflation information and a tire pressure/weight chart. The duals have different recommended pressures than the front tires.
Use LD's chart or the tire manufacturer's pressure chart for your tires.

Larry

I think you posted this previously, but this Michelin Guide for RV Tires basically covered all the bases and gave great information.  Thanks again!  Michelin Guide for RV Tires
Cheryl (a.k.a. Desert Diva)
1998 Lazy Daze (26.5 mid-bath)
2002 Honda CR-V
Re: Tire Pressure Calculation
Reply #8 –
You need to:

1. Load your LD as it would be at its maximum travel weight. Full fuel, full propane, in our case full water and empty gray and black tanks, full cargo, food, etc. and occupants in the seats where they normally travel. It might be easiest to do this at the start of a trip.

2. Go to a truck scale. Many truck stops have these or perhaps use Google maps to locate one. Weigh each axle separately and then the whole rig. That is, put just the front axle (both tires) on the scale and weigh. Then just the rear axle (all four tires) on the scale and weigh. Then both axles on the scale and weigh. As a cross check the axle weights should add up to the total weight (approximately). Contrary to a lot of RV opinion you do not need to weigh each tire or rear tire pair separately unless you're tying to correct some gross side-to-side or front-to-back cargo imbalances.

3. Go to your LD owner's manual. Use your front axle weight to determine the front tire pressure. Use the rear axle weight to determine the rear tire pressure.

4. Set the pressures cold, in the morning out of the sun, at the elevation you'll be traveling. I usually add 2-3 psi as a cushion.

5. This shouldn't be a problem, but in your case the cold inflation pressure should never exceed 80 lbs, the maximum inflation for your tires. If you need more pressure than that you need to reduce the load affecting those tires, either by moving the load around or removing some weight entirely.

Do not set different pressures side to side. Both front tires should have the same pressure. All four rear tires should have the same pressure. Adding the 2-3 psi I suggest will compensate for side-to-side weight variations.

If you don't have the LD owner's manual for your year and chassis LD perhaps someone else here does and can copy and send the tire inflation page to you. Or perhaps the LD factory could supply that.

If in doubt err on the side of more, not less pressure, provided you don't exceed 80 psi.
Terry
2003 26.5'RB
Gardnerville, NV
Re: Tire Pressure Calculation
Reply #9 –
I just did this using a Cat Scale at our local Flying J. The 3-part segmented scales allow you to place the front axle on the front segment and the rear axle on the middle segment, so it takes all the weights at one time. That makes it really simple and fast!
Greg & Victoria
2017 Mid-Bath  “Nocona” towing a manual 2015 Forester
Previously a 1985 TK
SKP #61264
Re: Tire Pressure Calculation
Reply #10 –
RE: CAT Scales

Most CAT and DOT scales actually have three scale pads.  With care, it is usually possible to place the steering wheels on the first pad, the dually wheels on the second, and the entire Toad on the third pad.  One can thus monitor weight for tire pressure management, as well as GCVWR compliance.  This is especially important when traveling in regions with mountain passes where FORD specifies de-rating of the GCVWR for altitude.

Warren
Warren
2019 MB “Dream Catcher”
Jeep Wrangler JL
Re: Tire Pressure Calculation
Reply #11 –
Quote from: WhiteElk  - 
 

This is especially important when traveling in regions with mountain passes where FORD specifies de-rating of the GCVWR for altitude.

When a high altitude pass causes you to exceed the GCVW with the derated power of the V10, engage wife drive.
Disconnect the Jeep and have her or any willing, licensed passenger, drive the Jeep separately to the top.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Tire Pressure Calculation
Reply #12 –
Indeed Larry, “Wife Drive” is a critically important feature when towing in the mountain states.  And, in case of my DW, she likes the opportunity to drive the Jeep! 
Warren
2019 MB “Dream Catcher”
Jeep Wrangler JL
Re: Tire Pressure Calculation
Reply #13 –
I just broke my own rule of disconnecting at 7,400 feet. Westbound on US40 over Rabbit Ears pass (to Steamboat Springs) is a gradual climb. I was lazy and towed up it to 9,400 at 38 to 44 mph.

Woohoo, Going down is a long 7 miles of 7%. I braked to allow second gear to engage to avoid using my brakes much. No way could I ascend eastbound towing.
Don & Dorothy
Sold our LD in June of 2023

Our boring always non-PC travel blog
Traveling Dorothy
Re: Tire Pressure Calculation
Reply #14 –
Quote from: Larry W  - 
When a high altitude pass causes you to exceed the GCVW with the derated power of the V10, engage wife drive.
Disconnect the Jeep and have her or any willing, licensed passenger, drive the Jeep separately to the top.

Larry

Sounds like my problem is that I mostl likely need a wife!... or maybe a passenger... but NO.  Solo all the way to the top.
Kristin
1997 MB
Re: Tire Pressure Calculation
Reply #15 –
Quote from: Kristin Lambert  - 
Sounds like my problem is that I most likely need a wife!... or maybe a passenger... but NO.  Solo all the way to the top.
Kristin

LOL...  I have the same problem - just took my RV back to storage and had to hook up the tow car.  However, the thought of making a bad "life choice" scares me more...
Cheryl (a.k.a. Desert Diva)
1998 Lazy Daze (26.5 mid-bath)
2002 Honda CR-V