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Old 07-27-2021, 12:52 PM   #1
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Tire pressure/load questions based on scale weight

I will try and keep this short but as detailed as possible. Finally got around to having RV weighed today so I can better determine tire pressure. I know the individual wheel weight is preferred, but not readily available for me, so CAT scale weight is what was done.

My unit is 2021 Entegra Odyssey 26M on Ford E450 . Tires are Hankook LT225/75R16, load index 115/112, speed rating S, load range E. The sticker on the door of cab states GVWR of 14500, GAWR 5000 front and 9600 rear. Max load listed on the tire states 2680 at 80 psi for single, 2470 @ 80 psi for dual. Sticker on door of motorhome states max cargo capacity 2068 lbs, GCWR 22000 lbs.

Unit came from dealer pretty much at max tire pressure with 75 psi in front and 80 psi rear.

Today's numbers at the scale: steer axle 3640 lbs, drive axle 10160 lbs, total 13800 lbs.

Now my questions.

1. According to the Hankook tire pressure chart for this tire, I should be able to run between 45-50 psi on the front. Is that possible? Seems too low to me.

2. According to the scale numbers, I am overweight in the rear, but not by much. I have a 150cc scooter, weight 250#, hitch carrier is 100# for a total of 350#. Receiver rating is 750#. For weighing purposes I did have a full 43 gal fresh water tank. We never travel with that much water. Usually just a few gal to use bathroom if needed. So, taking the weight of the water off, I am pretty much right on , I think, So I would have to run the rears at max pressure of 80 psi.

So all in all, I come up with 45-50 psi in front and 80 psi rear.

Am I close to being on the right track here? Thanks!!
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Old 07-27-2021, 01:19 PM   #2
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What are you trying to accomplish?
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Old 07-27-2021, 01:54 PM   #3
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As mentioned in the first paragraph, I want to regulate my tire pressure to something other than the max like it came from the dealer. I thought that it was too high, especially in the front. Based on the numbers mentioned, they say I can run 45-50 in front, seems low to me. Also I am a little disappointed that I am already at max in the rear with just the scooter and full water tank.
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Old 07-27-2021, 02:57 PM   #4
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I am in a similar situation with regards to the front axle. My front axle weighs roughly 3200 pounds which means 40 psi in the front tires. That seems too low to me as well. I put in between 5 to 10 psi more pending how I am feeling that trip.

There is something to be said about setting your tire pressure at sea level, then travelling into high altitude mountains which naturally increases your tire pressure by some amount, and also being mindful the reverse scenario.

MAKE SURE you have an accurate tire gauge. Read my findings about them by CLICKING HERE. I learned that my most trusted tire gauge was reading 9 psi too high which meant I was putting in 9 psi too little air.
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Old 07-27-2021, 03:32 PM   #5
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Thank you. I have learned that sometimes posts don't have enough information, but I guess I went overboard on this one. I have made a handful of trips running 75 in front 80 in rear because that is how it came to me. Felt like the front was always skating. Based on my weight numbers today and the tire manufacturers chart, I will go with 48 plus 10(just because 48 seems too low)and a max 80 in the rear.
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Old 07-27-2021, 04:15 PM   #6
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Originally Posted by rd36mnm View Post
Thank you. I have learned that sometimes posts don't have enough information, but I guess I went overboard on this one. I have made a handful of trips running 75 in front 80 in rear because that is how it came to me. Felt like the front was always skating. Based on my weight numbers today and the tire manufacturers chart, I will go with 48 plus 10(just because 48 seems too low)and a max 80 in the rear.
2 questions come to mind.
Did you ask the dealer why they had the tires inflated to max rear and 75 front? I would assume there was a reason they would stray so far above the recommended pressures.
What does "skating" mean? Do you mean it wanders? Except on wet or otherwise slipperty roads, I don't think going from 75 to 58 or vice versa, in inflation pressure, will make much handling difference. Soft tires will wander like harder ones, if the alignment is off, or there is some other front end or suspension problem. Your vehicle has a full wall slide I believe, and is heavier than those without, which may be a contributing factor.
If the object of the game is to improve the ride by softening the tires, you may be disappointed, as these things aren't meant or able to ride like a Cadillac.
In my opinion.
Good luck with it, either way.
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Old 07-27-2021, 05:02 PM   #7
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The dealer didn't stray on any pressures, they went by the Federal placard numbers.

They are not going to sell it with less then what's called for.
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Old 07-27-2021, 05:08 PM   #8
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You have a scooter and carrier on the back.

How far out from where a ball would sit is that weight ?
Tongue weight is at the ball, not a foot or 2 behind it. That leverage can unload the front axle, adding weight to the rear.
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Old 07-27-2021, 05:14 PM   #9
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No I did not ask the dealer. They received from another dealer, had less than 18hrs to turn it around for me to pick up which I drove 300 miles to get. Alignment is fine, no pull either direction, hands off wheel easily. It handles about what I expected for a 14000 pound box running down tne road. I had no idea if the tire pressure would make a difference or not. I am not a tire expert. After reading so many posts about the importance of tire pressure and determining that by weight, I thought it prudent to get it weighed and ask the questions I did.
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Old 07-27-2021, 06:09 PM   #10
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You have a scooter and carrier on the back.

How far out from where a ball would sit is that weight ?
Tongue weight is at the ball, not a foot or 2 behind it. That leverage can unload the front axle, adding weight to the rear.
Thanks....that makes sense. Even though it's only 350#, it is about a foot back from the receiver.
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Old 07-28-2021, 05:00 AM   #11
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Quote:
Originally Posted by rd36mnm View Post
No I did not ask the dealer. They received from another dealer, had less than 18hrs to turn it around for me to pick up which I drove 300 miles to get. Alignment is fine, no pull either direction, hands off wheel easily. It handles about what I expected for a 14000 pound box running down tne road. I had no idea if the tire pressure would make a difference or not. I am not a tire expert. After reading so many posts about the importance of tire pressure and determining that by weight, I thought it prudent to get it weighed and ask the questions I did.
The bottom line is that the front tire pressure of 75 PSI is because that is what is required by Hankook for the tires and the front axle to support 5000 lbs. You are not supporting 5000 lbs on the front and you should air the tires based on the weight they are carrying plus 5 PSI. I spent some time working on weight-in-motion-scales and that is where I learned about the tire footprint. To much air for the weight the tire is carrying will reduce the size of the footprint and drag but will cause poor tire wear, a harsh ride, and make the steering feel loose. The tire manufacturer has done a lot of testing and that is where they came up with the inflation tables. Go with what they require based on weight. The sticker on the door jam is always going to go with the weight rating of the axle.

On the rear (we are in the same boat as you) Ford has shipped the chassis with the load rang E tire because that is sufficient for the 9600 lb rating of the axle. That means the rear tires are going to be at the maximum of 80 PSI. In my opinion we should be running Load Range F tires on the rear because there is no margin on the Load Range E. When and if we replace the rear tires it will be with Load Range F.
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Old 07-28-2021, 08:13 AM   #12
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In my opinion we should be running Load Range F tires on the rear because there is no margin on the Load Range E. When and if we replace the rear tires it will be with Load Range F.
I am curious. Why do you feel the high capacity load range E tires are insufficient? They claim to handle a minimum of 500 extra pounds per tire compared to typical load range "E" tires. That means a minimum of 2000 extra pounds of capacity in back.

Michelin offers two different Agilis CrossClimate tires for class C motorhomes. One is standard "E", the other has an added "C". I think it means "Commercial". That "C" can handle roughly 25% more weight.
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Old 07-28-2021, 09:49 AM   #13
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Concerning GAWR,, I know there are lots of people out there that have no problem exceeding it by 560 lbs. Doing that would bug me too much so I'd have to figure out something else to give me more peace of mind.

I know it's not pretty but my first thought would be to mount a hitch up front to carry the scooter on. That would pretty much get the rig back to a more proper weight distribution.

On tire pressure, looks like 80 psi is it for the rear. Would have to do some experimenting up front (keep psi above minimum) to see what works better.
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Old 07-28-2021, 11:07 AM   #14
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Thank you all, I now have my answers. I will max the rear at 80 psi and drop the fronts to the inflation table plus 5-10 and experiment. Not traveling with a full water tank, which we never do, should bring me to within GAWR on the rear. If we ever become long haul travelers, then things would change and I would look into a front hitch, but for the time being, we are pretty much doing short 200-350 miles round trip, so should be OK.
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