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Here are the "rules" I use.


First, running tires more than 5 psi over OR under the inflation required for a given weight will increase tire wear.


Second, each tire in a dually configuration (rear) will carry less weight at the same inflation than the same tire in a single configuration (front), but I have four tires sharing the load in the rear.


My '03 LS Crew Cab 3500 weighs 4010 front and 3120 rear unloaded. About 60% or the driver and front seat passenger weight goes on the front tires, and about 55% of any rear seat weight goes on the front. I measured the approximate center of the "load" from the front axle and the rear axle to determine this.


Now, for actual pressures in my stock LT215/85R16 tires:


Front singles: 55psi carries 4100 lbs, 60 psi carries 4360, and 65 psi (max for my tires) carries 4670 (FAWR). So I run 65 psi front.


Rear duals: 40 psi carries 5960, 45 psi carries 6500, 50 psi carries 7060, 55 psi carries 7460, 60 psi carries 7940, and 65 psi carries 8600 (RAWR is 8550). As I recall, I should actually be running 35 PSI rear when empty, but since the load changes frequently, I leave them at 45 psi when not towing. This results in a harsher ride than 35 or 40, but I don't have to air up and down several times a day. Also, my experience has taught me to always run about 5 or 10 psi higher than the actual load requires to maximize tire life (at the expense of a soft ride).


Transferring these numbers to your load, I would run the fronts at 65 psi at all times, and the rears at 40 when empty, and maybe 50 or 55 loaded with your 5er and gear.


Hope this helps,


Ralph
 

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Washboy,


Yes, it looks like you got it. Just be careful that you're reading the right lines in the chart, since the "tires used as singles" and "tires used as duals" are different values.


Also, don't forget to allow for that 60/40 distribution for the front seat. And even though the charts might indicate you need no air in the rear when empty, I don't think I'd ever run them less than 35 psi.


Ralph
 
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