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post #1 of 2 Old 05-19-2013, 08:53 AM Thread Starter
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Pressure Question

I am running 35x12.50R18 Toyo OpenCountry MTs with 60 psi in them. Is this too much? I also have noticed my mpgs have gone down a bit from running the higher pressure. I had only 35psi in them before, but I think that just wasnt enough. Any thoughts?

Wifes ride 2006 Crew Cab F350 With Rancho Lift Kit and 35X12.50R18 Toyo Open Country MTs

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post #2 of 2 Old 05-19-2013, 10:44 AM
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That your mpg went down from higher psi is the opposite of what's supposed to happen. Higher psi, to a certain degree, reduces rolling resistance and will also make you ride on less of the tread, depending on wheel width. A 12.5" wide tire on an 8" wheel at 60 psi is going to go bald in the center and have deeper tread on the outsides.

To find optimum tire wear, run chalk across the tread and adjust the psi to until it all scrubs off. I would start at max psi, then reduce psi until the chalk mark is scrubbed off. However, this only works on NEW tires. Older tires will have a flat surface to the road, but tread depth across the tire can vary. I run 315-75-16s on a 10 inch wheel and 40~45 psi is my optimum psi for best tread wear.

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