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Old 07-17-2011, 01:14 PM   #1
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Tire Pressure

My first trip out this year I went to max pressure due to not being able to get weighed. It was a rough ride. Finally got to a scale (Weigh station) and got weights. Only thing missing was 1/2 tank fuel, about 240lbs. I was only able to get total axle and right side weights, so left are right subtracted from total. The following is what I got:

Front axle = 6240
Rear axle = 11280

Front right = 2960
Front left = 3280 So I assume to inflate axle tires for 3400lbs?

Right rear = 5860
Right left = 5420 Again, inflate axle tires for 3000lbs? Dually's

Is it common for side to side weight to be off like that?

What would you run for tire pressures? The chart I have doesn't go as low with weights I have figured. I am running GY G670 245/70R/19.5 F.

Thanks for any insight......
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Old 07-17-2011, 03:46 PM   #2
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70 PSI Front & Rear will give you a cushion for fuel/water/holding tanks.
If front tires start to show any riveing. Add 10 PSI more.

Yes its normal for weight to be different side to side.
Main reason 4 corner weights are recommended.
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Old 07-17-2011, 04:45 PM   #3
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I need help too! I have a 2001 ult adv Winnebago dp. The front axle weighs 9600 lbs, the rear 15,860 lbs. Full of fuel and goodies. Front tires are Mich 275/80 22.5 rated 3250 single. Rear tires are Kelly 295/75R 22.5 rated 5676 lbs dual. I have looked at charts until I am confused. How much air should I be running in these tires? Thanks for your input, Don
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Old 07-17-2011, 08:08 PM   #4
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I need help too! I have a 2001 ult adv Winnebago dp. The front axle weighs 9600 lbs, the rear 15,860 lbs. Full of fuel and goodies. Front tires are Mich 275/80 22.5 rated 3250 single. Rear tires are Kelly 295/75R 22.5 rated 5676 lbs dual. I have looked at charts until I am confused. How much air should I be running in these tires? Thanks for your input, Don

Don, kinda new at this so maybe I'm missing something. I look at your info. stating your front tires are rated for 3250, which when doubled to add the capacity of a second tire, equals 6500 pounds. You say the front axle weight is 9600? This makes you 3100 lbs overweight on the front axle, no? Same scenario in the back as well? Thinking if this is true, no amount of air pressure is going to be right. At minimum, you should be hunting for tires with much more capacity. 5000+ for the front, and 4000+ for the rear.
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Old 07-17-2011, 08:18 PM   #5
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Don, kinda new at this so maybe I'm missing something. I look at your info. stating your front tires are rated for 3250, which when doubled to add the capacity of a second tire, equals 6500 pounds. You say the front axle weight is 9600? This makes you 3100 lbs overweight on the front axle, no? Same scenario in the back as well? Thinking if this is true, no amount of air pressure is going to be right. At minimum, you should be hunting for tires with much more capacity. 5000+ for the front, and 4000+ for the rear.
I'm betting we're missing something in the translation here. We need to know the load range of your tires... usually stated "LRX" with X=load range. What do you mean when you say your tires are "rated" at XYZ? What charts have you been looking at?

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Old 07-17-2011, 08:47 PM   #6
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Quote:
Originally Posted by taboky View Post
My first trip out this year I went to max pressure due to not being able to get weighed. It was a rough ride. Finally got to a scale (Weigh station) and got weights. Only thing missing was 1/2 tank fuel, about 240lbs. I was only able to get total axle and right side weights, so left are right subtracted from total. The following is what I got:

Front axle = 6240
Rear axle = 11280

Front right = 2960
Front left = 3280 So I assume to inflate axle tires for 3400lbs?

Right rear = 5860
Right left = 5420 Again, inflate axle tires for 3000lbs? Dually's

Is it common for side to side weight to be off like that?

What would you run for tire pressures? The chart I have doesn't go as low with weights I have figured. I am running GY G670 245/70R/19.5 F.

Thanks for any insight......
Been spending too much time around Wayne the Marine haven't you.
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Old 07-18-2011, 04:54 AM   #7
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Yes it is common to have that much weight diff. Mine has the refg, washer dryer, 3 8D house batts, charger/inverter all on the left side. You will need to set your tire pressures for the highest weight on each axle, and all pressures should be the same in all tires on an axle.
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Old 07-18-2011, 06:54 AM   #8
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Quote:
Originally Posted by wingman8 View Post
I need help too! I have a 2001 ult adv Winnebago dp. The front axle weighs 9600 lbs, the rear 15,860 lbs. Full of fuel and goodies. Front tires are Mich 275/80 22.5 rated 3250 single. Rear tires are Kelly 295/75R 22.5 rated 5676 lbs dual. I have looked at charts until I am confused. How much air should I be running in these tires? Thanks for your input, Don
I am sorry but I gave the rating on the front tires in KG not LBS. They are rated at 7,160 lbs. This gives me 14,329lbs on the front which weighs 9,600 lbs. Rear tires rated at 5,675 lbs dual so is that 22,700 lbs for the rear axle with 4 of them? Please bear with me on this, I'm old. Thanks, Don
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Old 07-18-2011, 07:02 AM   #9
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Quote:
Originally Posted by wingman8 View Post
I am sorry but I gave the rating on the front tires in KG not LBS. They are rated at 7,160 lbs. This gives me 14,329lbs on the front which weighs 9,600 lbs. Rear tires rated at 5,675 lbs dual so is that 22,700 lbs for the rear axle with 4 of them? Please bear with me on this, I'm old. Thanks, Don
Old is good Don or at least it beats the alternative. You're on the right track with your weights and pressures.

In your situation I would pressurize the front tires for the highest weight plus add 10% to that weight for safety margin. Always round up on the tire charts. Like wise on the rears.
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Old 07-18-2011, 01:18 PM   #10
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Quote:
I need help too! I have a 2001 ult adv Winnebago dp. The front axle weighs 9600 lbs, the rear 15,860 lbs. Full of fuel and goodies. Front tires are Mich 275/80 22.5 rated 3250 single. Rear tires are Kelly 295/75R 22.5 rated 5676 lbs dual. I have looked at charts until I am confused. How much air should I be running in these tires? Thanks for your input, Don
For the front you need to allow for 9600/2 plus a safety margin for side-side imbalance. For the rear, 15860/4 + safety margin. I would allow at least a 5% for imbalanced load, so 9600/2 + 5% = 4800 + 240 = 5040 lbs on the front tires and 15860/4 + 5% = 3965 + 198 = 4163 lb on each rear.

The 3250 kg "rating" is the max load for a Load Range H Michelin 275/80, so using the table for that tire I get 80 psi (which will carry 5140 lbs). I would bump that up to 85 psi for some extra margin.

I don't have a Kelly tire inflation table.
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Old 07-18-2011, 02:51 PM   #11
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Quote:
Originally Posted by Triker56 View Post
70 PSI Front & Rear will give you a cushion for fuel/water/holding tanks.
If front tires start to show any riveing. Add 10 PSI more.

Yes its normal for weight to be different side to side.
Main reason 4 corner weights are recommended.
70? That seems low, doesn't it? The chart only goes down to 80 with weights. I guess they didn't expect that tire to carry that light a load. It is a 22k chassis. Guess I need to accumulate more crap
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Old 07-18-2011, 09:42 PM   #12
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Thanks for your advice Gary. I tried 95lbs in the front and drove about 75 miles and checked them. They were up to 110 lbs, of course it has been over 100 degrees here for a long time. Hard telling what the highway temp was. I'm sure the hot weather didn't help any. After blowing several tires off of my 40' toyhauler with the recomended 80lbs air I am getting gun shy, very expensive. I want to do all I can to keep this MH from bolwing tires, thanks again. Don
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Old 07-18-2011, 10:03 PM   #13
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Quote:
Originally Posted by wingman8 View Post
I am sorry but I gave the rating on the front tires in KG not LBS. They are rated at 7,160 lbs. This gives me 14,329lbs on the front which weighs 9,600 lbs. Rear tires rated at 5,675 lbs dual so is that 22,700 lbs for the rear axle with 4 of them? Please bear with me on this, I'm old. Thanks, Don
By Federal law and most state laws the rear axle can only be rated for 20,000#'s even though the tires can support more, UNLESS you have a tag axle. This is called the Bridge Gross Weight Formula of the Federal Bridge Law
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Old 07-18-2011, 10:04 PM   #14
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70? That seems low, doesn't it? The chart only goes down to 80 with weights. I guess they didn't expect that tire to carry that light a load. It is a 22k chassis. Guess I need to accumulate more crap
If the weight chart starts at 80psi then that is the minimum you need even if your rig weighs less.
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