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Old 07-31-2021, 05:34 PM   #1
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Weight distribution / air pressure question

Beaver Monterey 1998 30 ft DP

CAT 330

(Onan 6.5kw rear mounted)



known rear heavy but surprised at the actual numbers


front: 6340 lbs
rear: 15,300 lbs


near full fuel (around 88 gallons)
empty fresh water (100 gal tank near center of axles)

3 kids and two adults
mostly empty storage and kitchen due to dramatic decline in health and getting ready to sell.


how much air should I put in the 225 Toyo tires
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Old 07-31-2021, 05:46 PM   #2
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Quote:
Originally Posted by minus 200 View Post
Beaver Monterey 1998 30 ft DP

CAT 330

(Onan 6.5kw rear mounted)



known rear heavy but surprised at the actual numbers


front: 6340 lbs
rear: 15,300 lbs


near full fuel (around 88 gallons)
empty fresh water (100 gal tank near center of axles)

3 kids and two adults
mostly empty storage and kitchen due to dramatic decline in health and getting ready to sell.


how much air should I put in the 225 Toyo tires
Google “toyo tire load chart” and find your tires, using your weights find the air pressures.
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Old 07-31-2021, 06:55 PM   #3
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Look up your tire size and weight here.

https://www.toyotires.com/media/2155...ion_tables.pdf
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Old 08-01-2021, 07:03 PM   #4
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What is listed on the Federal Tire Placard in the MH? That is for GVWR for your MH.
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Old 08-02-2021, 10:36 AM   #5
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Quote:
Originally Posted by Crasher View Post
Look up your tire size and weight here.

https://www.toyotires.com/media/2155...ion_tables.pdf
The EXACT answer!!
Scott
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Old 08-02-2021, 06:35 PM   #6
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Ok so let me ask a question about the caclualtion of the correct air pressure based upon axle weights. I saw a post about how they calculate pressures when you use a CAT scale that only will give Axle weights not each individual tire.



My coach front axle Total wt 7500.00 Rear15,420 loaded as i drive it, full of fuel half of water plus gear.



Using my front axle as the example
1. 7500/2 for each tire = 3750

2. multiply by 5% to account for not having axle end weight 1.05x 3750= 3938
3. look up the single load that is equal to or above 3938= 80 Psi

4. THEN they the recommend adding 10% to that pressure for safety margin 80 x 1.10=88psi.



so my question is, is it commonly accepted to add 5% for not having individual tire wts vs. total axle weight and is is also accepted to add on 10% for additional safety margin.

On my rears that calculation came to 94 Psi.



coach Gross weight is 22,920
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Old 08-02-2021, 07:11 PM   #7
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Seems like 10% and 5% is for same thing different margins.
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Old 08-02-2021, 07:26 PM   #8
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Quote:
Originally Posted by ftodaro View Post
Ok so let me ask a question about the caclualtion of the correct air pressure based upon axle weights. I saw a post about how they calculate pressures when you use a CAT scale that only will give Axle weights not each individual tire.



My coach front axle Total wt 7500.00 Rear15,420 loaded as i drive it, full of fuel half of water plus gear.



Using my front axle as the example
1. 7500/2 for each tire = 3750

2. multiply by 5% to account for not having axle end weight 1.05x 3750= 3938
3. look up the single load that is equal to or above 3938= 80 Psi

4. THEN they the recommend adding 10% to that pressure for safety margin 80 x 1.10=88psi.



so my question is, is it commonly accepted to add 5% for not having individual tire wts vs. total axle weight and is is also accepted to add on 10% for additional safety margin.

On my rears that calculation came to 94 Psi.



coach Gross weight is 22,920
This is a common formula. The 5% is to account for any difference side to side and the 10% is a safety margin to deal with outside temperature changes that affect tire pressures. Most will apply this formula on a 60 degree morning before the tire has rolled or warmed from exposure to the sun.
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Old 08-02-2021, 11:37 PM   #9
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Quote:
Originally Posted by ftodaro View Post
Ok so let me ask a question about the caclualtion of the correct air pressure based upon axle weights. I saw a post about how they calculate pressures when you use a CAT scale that only will give Axle weights not each individual tire.



My coach front axle Total wt 7500.00 Rear15,420 loaded as i drive it, full of fuel half of water plus gear.



Using my front axle as the example
1. 7500/2 for each tire = 3750

2. multiply by 5% to account for not having axle end weight 1.05x 3750= 3938
3. look up the single load that is equal to or above 3938= 80 Psi

4. THEN they the recommend adding 10% to that pressure for safety margin 80 x 1.10=88psi.



so my question is, is it commonly accepted to add 5% for not having individual tire wts vs. total axle weight and is is also accepted to add on 10% for additional safety margin.

On my rears that calculation came to 94 Psi.



coach Gross weight is 22,920
Well,
In all my RV years and using the provided tire pressure charts for the brand of tires I had at the time, I have never added any percentage. I look at their chart, find my tires and, find the weight I'm applying to either single or dual and, fill my tires to those pressures, done. So far, in oh, maybe 150K of RV miles, no issues, no odd wear, no ill handling effects of the coaches we've had, nothing. And I've never, ever done a four corner weight thing. As stated, I can't move anything anyways. All my stuff fits where it is, period.
Scott
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Old 08-03-2021, 04:46 AM   #10
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Quote:
Originally Posted by ftodaro View Post
Ok so let me ask a question about the caclualtion of the correct air pressure based upon axle weights. I saw a post about how they calculate pressures when you use a CAT scale that only will give Axle weights not each individual tire.



My coach front axle Total wt 7500.00 Rear15,420 loaded as i drive it, full of fuel half of water plus gear.



Using my front axle as the example
1. 7500/2 for each tire = 3750

2. multiply by 5% to account for not having axle end weight 1.05x 3750= 3938
3. look up the single load that is equal to or above 3938= 80 Psi

4. THEN they the recommend adding 10% to that pressure for safety margin 80 x 1.10=88psi.



so my question is, is it commonly accepted to add 5% for not having individual tire wts vs. total axle weight and is is also accepted to add on 10% for additional safety margin.

On my rears that calculation came to 94 Psi.



coach Gross weight is 22,920
I should have added that the placard on the coach recommends 100 Psi. I am about 3300 lbs under the GVWR rating and I am coming in at 88 front and 94 Rear.
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Old 08-03-2021, 07:05 AM   #11
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I should add to my previous post that although adding 10% for "safety" or temp changes is an accepted practice, I do not add the 5% or the 10%. Maybe 3-4 psi extra, but no more. Never had any tire issues. The last set I replaced at 5 years with 50,000 miles showed slightly less tread on the centers than outer edges. That would indicate running with slightly higher pressure than needed. Slightly higher is better than lower, so I continue to use the same practice.
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