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Thread: Tire PSI
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Old 11-18-2020, 08:41 PM   #19
Junior Member
Brand: Still Looking
State: Europe
Posts: 14
THOR #7351
Originally Posted by Sdkim View Post
Hello everyone,

I have a 2020 Challenger 37FH. The tire size is 255/80 R22.5 XRV. The rv weighs in at 7,890 lbs front axle, 15,990 lbs rear axle.

I was advised to fill my tires at 110 psi for all six tires.

Does this sound right?

Thanks in advance.
With my made spreadsheet , it comes to Front 91 psi and rear 100 psi.

Disclaimer: you yourselfe are responcible for the given axleweights . And that is where it goes wrong often. Best is weighing per axle-end, second best per axle, in the loading ( also persons and pets) you drive with ( dont forget the water).

My advice is calculated with a formula that leads to higher pressure then the officially used, and I first add 10% to the load.
Your trucktires are most likely calculated in maximum load for 120kmph/75mph, and sometimes I even calculate for as if 160kmph/99mph. This together with the 10% adding, it gives highest reserve, with still acceptable comfort and gripp.
Will give those psi too. FRONT 102 PSI , REAR 103 PSI.
But this is still no 110 psi.
For this I lowered the single maxload for every 10kmph by 1 loadindex step, so front 138 -4=134
and rear from 135 to 134 only , because duall load already have lesser deflection.
That exlplaines the only 3 psi higher for rear, while front goes from 91 psi to 102 psi.

So if you are certain of the axleweights, first lower to front 100 and rear 105psi. Then if comfort is acceptable, dont go lower. Especially the 10 psi lower on front is noticed by driver and codriver in comfort,because seated close to the front-axle.
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