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Old 03-18-2015, 06:42 PM   #1
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What's my tire pressure????

here's what I got.... the tires are 275-70-22.5....

on the scale. the most I have ever weighed in the front is 7,040 lbs...
on the rear 17,400 lbs...

the rear includes tounge weight of trailer...
the front is lighter with the trailer so the weight is with out....

like to see what you come up with...
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Old 03-18-2015, 06:59 PM   #2
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Front tires = 3520lbs (div 2)
Rear tires = 4350lbs (div 4)

From the Inflation tables,

http://www.firestonetrucktires.com/p...Load_Table.pdf

The minimum cold pressure to support these weights is

Front = 85psi (4920lbs)
Rear = 85psi (4590lbs)

The pressure is the minimum in the table, it doesn't go lower, The weight is what is listed for that pressure)
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Old 03-18-2015, 07:27 PM   #3
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Quote:
Originally Posted by Waiter21 View Post
Front tires = 3520lbs (div 2)
Rear tires = 4350lbs (div 4)

From the Inflation tables,

http://www.firestonetrucktires.com/p...Load_Table.pdf

The minimum cold pressure to support these weights is

Front = 85psi (4920lbs)
Rear = 85psi (4590lbs)

The pressure is the minimum in the table, it doesn't go lower, The weight is what is listed for that pressure)
thanks for posting,,... so is that where you would run them???
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Old 03-18-2015, 09:05 PM   #4
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What does the tire placard in the MH state to run? If you run the minimum required to support the weight, the tires are operating at their maximum limit continually. You might find this pdf from the Rubber Manufacturers Association interesting http://www.mcgeecompany.com/wp-conte...ete-manual.pdf Scroll down to page 55, which addresses MotorHome tires. The right side of the page states: However, the tires should never be operated at less than the mfgrs. tire placard pressures.
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Old 03-19-2015, 12:42 AM   #5
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What does the tire placard in the MH state to run? If you run the minimum required to support the weight, the tires are operating at their maximum limit continually. You might find this pdf from the Rubber Manufacturers Association interesting www.mcgeecompany.com/wp-content/uploads/2010/12/complete-manual.pdf Scroll down to page 55, which addresses MotorHome tires. The right side of the page states: However, the tires should never be operated at less than the mfgrs. tire placard pressures.
my new motorhome came with 255-70-22.5's I changed them to 275-70-22.5's...
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Old 03-19-2015, 01:32 AM   #6
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Direct from the tire manufacturers the correct info is:
The pressure on the sidewall of a Michelin RV tire and many others is not the "Maximum" the tire should ever have (unlike car tires) it is the minimum to support the maximum rated carrying capacity of the tire.

From the Michelin RV Tire Guide:
Quote:
"If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."
From page 6 of the GoodYear RV Tire and Care Guide:
Quote:
"How much air is enough?
The proper air inflation for your tires depends on how much your fully loaded RV or trailer weighs. Look at the sidewall of your RV tire and you’ll see the maximum load capacity for the tire size and load rating, as well as the minimum cold air inflation, needed to carry that maximum load."
From TOYO:
Quote:
Q: What are the consequences of inflating the tires to accommodate the actual loads?
A: If the inflation pressure corresponds to the actual tire load according to the tire manufacturer’s load and pressure table, the tire will be running at 100% of its rated load at that pressure. This practice may not provide sufficient safety margin. Any air pressure loss below the minimum required to carry the load can result in eventual tire failure.
But then they go ahead and publish a weight/pressure chart allowing lower pressure for RV's!!

From the August 2010 Motorhome Magazine "Tread Carefully" tire article:
Quote:
The maximum load capacity allowed for the size tire and load rating and the minimum cold air inflation needed to carry that maximum load are
located on the tire’s sidewall.
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Old 03-19-2015, 05:14 AM   #7
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See what your placard says, It should give a tire size, pressure, and max weight.

Since the actual weights are well below published pressure weights, I'd probably go with 85psi cold.

Front actual weight = 3520lbs.. Max weight for 85psi is 4920lbs
Rear actual weight = 4350lbs.. Max weight for 85psi is 4590lbs

The tire charts post a minimum and maximum pressures and corresponding weights that can be supported for the tire if its mounted as a single or a dully.

For that tire its minimum 85 psi, maximum 120 psi.

I would not exceed 120 psi with that tire. Max weights at that pressure are 7000 lbs (single) and 6395 lbs (dully)
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Old 03-19-2015, 06:13 AM   #8
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Quote:
Originally Posted by Mr_D View Post
Direct from the tire manufacturers the correct info is:
The pressure on the sidewall of a Michelin RV tire and many others is not the "Maximum" the tire should ever have (unlike car tires) it is the minimum to support the maximum rated carrying capacity of the tire.

From the Michelin RV Tire Guide: From page 6 of the GoodYear RV Tire and Care Guide:From TOYO:But then they go ahead and publish a weight/pressure chart allowing lower pressure for RV's!!

From the August 2010 Motorhome Magazine "Tread Carefully" tire article:
thanks for the post, with all the info here,...what pressure would you run?
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Old 03-19-2015, 06:26 AM   #9
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Originally Posted by Waiter21 View Post
See what your placard says, It should give a tire size, pressure, and max weight.

Since the actual weights are well below published pressure weights, I'd probably go with 85psi cold.

Front actual weight = 3520lbs.. Max weight for 85psi is 4920lbs
Rear actual weight = 4350lbs.. Max weight for 85psi is 4590lbs

The tire charts post a minimum and maximum pressures and corresponding weights that can be supported for the tire if its mounted as a single or a dully.

For that tire its minimum 85 psi, maximum 120 psi.

I would not exceed 120 psi with that tire. Max weights at that pressure are 7000 lbs (single) and 6395 lbs (dully)
so at 85 psi I could run up to a maximum of 14,000 lbs front and 20,000 lbs rear..correct

so, with that being said... @ 85psi and loaded weight of 7000 lbs front...I'm only at 50% of max load weight for that tire @ that air pressure???


and @ 85psi and loaded weight of 17,400 rear I'm at 87% of max load weight for that tire @ that air pressure?????


giv'n that added info.....
what would you say the best load to psi ratio is ... in percentage????


would you want all the tires to be the same percentage ???


or does that even matter???




to get to 80% on the rear is 100 psi
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Old 03-19-2015, 08:08 AM   #10
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Quote:
so at 85 psi I could run up to a maximum of 14,000 lbs front and 20,000 lbs rear..correct
NO, that is not correct - The weights are for each tire, not each axle.

Please refer to the table, find your tire, then you can look at the pressure vs load.

According to the table, at 85psi cold, the maximum weight your tire will support is:

Front tire - 4920lbs .. Front axle = (4920 * 2 = 9,840lbs)

Dully tire - 4590lbs .. Rear axle = (4590 * 4 = 18,360lbs)

The pressures from the table are Minimum pressure for that load. You can put in higher pressure if you wish, I would not exceed 120psi for that particular tire.

You must also consider "What is the pressure when the tire is hot?. That pressure should not exceed 120psi (the max for your tire)
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Old 03-19-2015, 09:42 AM   #11
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NO, that is not correct - The weights are for each tire, not each axle.

Please refer to the table, find your tire, then you can look at the pressure vs load.

According to the table, at 85psi cold, the maximum weight your tire will support is:

Front tire - 4920lbs .. Front axle = (4920 * 2 = 9,840lbs)

Dully tire - 4590lbs .. Rear axle = (4590 * 4 = 18,360lbs)

The pressures from the table are Minimum pressure for that load. You can put in higher pressure if you wish, I would not exceed 120psi for that particular tire.

You must also consider "What is the pressure when the tire is hot?. That pressure should not exceed 120psi (the max for your tire)
lol...thanks ... I knew I had some thing screwed up

I doubled the already doubled weight
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Old 03-19-2015, 09:47 AM   #12
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NO, that is not correct - The weights are for each tire, not each axle.

Please refer to the table, find your tire, then you can look at the pressure vs load.

According to the table, at 85psi cold, the maximum weight your tire will support is:

Front tire - 4920lbs .. Front axle = (4920 * 2 = 9,840lbs)

Dully tire - 4590lbs .. Rear axle = (4590 * 4 = 18,360lbs)

The pressures from the table are Minimum pressure for that load. You can put in higher pressure if you wish, I would not exceed 120psi for that particular tire.

You must also consider "What is the pressure when the tire is hot?. That pressure should not exceed 120psi (the max for your tire)
so then,... the FRONT @ 85 psi has a load rating of 10,000 which is 70% of the load rating

so then the question still remains...

what is the magic formula for picking tires the will have a dual purpose

what percent of maximum do you say is the weight to load rating
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Old 03-19-2015, 09:55 AM   #13
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NO -

The load rating is 9840 max if you inflate to 85psi. That number comes from the table that you need to refer to.

That table will give you the load rating at different pressures.

If you wish to carry 10,000, you will need to increase the pressure to at least 90psi, That will provide a maximum load of 5160 lbs per tire for a single tire load, or 10,320lbs maximum for your front axle.

What do you mean by "Dual Purpose" tires?
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Old 03-19-2015, 10:06 AM   #14
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NO -

If you put 85 psi in your front tires, the maximum load you can carry in the front is 9,840 lbs.

If you wish to carry 10,000 lbs in the front, you will need to increase the pressure in the front tires.
ok, I round' off the 10k

so I'm at 71.5 %

the question still whats the rule of thumb ... the happy camper...the I'm in the money... the clam on high tide/..the cutt'n a fat hog..percentage???
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