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Old 05-24-2013, 10:41 AM   #1
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Yet another tire inflation question, but with a twist

I've searched through the forums but all I could find referenced too much air. I have a 99 Winnebago Chieftain, class A, 33 foot, bought it in April. The previous owner installed brand new Roadmaster RM170 245/70-19.5 (made by Cooper). The inflation tables for this tire don't even go down to my current weights! Let me clarify.

I am loaded up and ready for this weekend. I took the coach to get weighed last night and my front weight is 6020, rear weight is 11300. GAWR's are 7000 and 13500.

These tires have a max weight of 4540 @110 psi single and 4300 @ 110 psi dual. Doing the math: Max weight * 2 (4 for dually), divided by max psi = X. Then actual weight divided by X.

Front axle: 4540*2 = 9080, divided by 110 = 82.55. 6020/82.55 = 73 psi.
Rear axle: 4300*4 = 17200, divided by 110 = 156.36. 11300/156.36= 73 psi.

For my actual weights I should be running 73 psi all around. The inflation tables start at 3640 @ 80 psi single (a weight that actually exceeds my front axle GAWR), and 3415 @ 80 psi dual (a weight that actually exceeds my rear axle GAWR). It's obvious that the previous owner installed over-rated tires.

Here's my question, is it safe to run the tires at 73 psi for my actual weights or should I stick with the inflation tables and run the minimum on the tables, 80 psi?

Thanks,
Shawn
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Old 05-24-2013, 10:57 AM   #2
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Run the minimum in the tables. You need a minimum pressure to keep the beads secure in the rims.
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Old 05-24-2013, 10:58 AM   #3
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I would'nt go below the min on the tables. 80psi
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Old 05-24-2013, 11:09 AM   #4
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Thanks guys!
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