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Discussion Starter #1
This is about as sexy as John Goodman in a speedo but it definitely works, particularly for heavy pickups.

Keep your tires aired up rock-hard.

This is a must for folks with firebomb tires but it makes a big difference on other brands as well.

I use 235-85 E rated tires and I keep them inflated to 80 psi, front and rear. Any more and the tire starts to "crown" - bulge out in the middle of the tread. That will wear the center of the tire out quickly. Not recommended.

My truck is very sensitive to this. If the tires get down to 70 psi, I lose 1 MPG. At 60 psi, 3 MPG. Ask me how I know that. Don't gundeck the tire inflation.
 

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The Unseen Mod
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well my PJ's say 65psi but it didnt wear right so I played with the air, maybe this time i will leave it at 65psi and see how it goes I used to get good mileage to.
 

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Discussion Starter #3
Use the max pressure listed on the sidewall. That is generally the crowning pressure. The pressure will be much less for C or D rated tires.

It will ride rough but MPG will improve.
 

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Don't EFN worry about it
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In my case I am just fouled I guess. I run 285-75-16s on my stock alum. wheels. I really need 10 " wheels to get proper foot print. My other 97 I had 235-85s and they were aired up to 80 but it was a 2wheel drive and I drove it out of town alot.
 

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The Unseen Mod
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I dont mind the ride I've never had anything smaller then a 33 lol so im used to it. should I back it off some it wears wrong like the center my buddy got 50k on his 38 Pj's
 

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AllYourBaseAreBelongToUs
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Maybe that's part of why I only get about 14mpg. I ride around at race psi front and rear everywhere. :D
 

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Hog Whisperer
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Ok I got a 6700lb F250 I run Yokohama geolanders 285 75 16. wHAT do I run front pressure and rear pressure for good ride and best tread wear? At 600 for four I need to know. Tate
 

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i have been running 55 in my 305s the max it 65
 

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AllYourBaseAreBelongToUs
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I'm gonna try that on my trip to Panama City this weekend and see what happens. I'll post the results.
 

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Discussion Starter #12
Go for it! Gotta admit this is one of the cheapest things you can do to improve MPG.

As a rule the pressure on the sidewall is the "crowning" pressure. If I remember right, it is generally 35 psi for "C" rated tires, 65 psi for "D" rated tires and 80 psi for "E" rated tires.
 

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my 305s are E rated but only have a max psi of 65. i think it has to do with the volume of air or something like that
 

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Hog Whisperer
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Is there not some consideration for front engine weight on the tires and the lack of weight on the rear tires? or is MPG and tire wear two different things? How can the max pressure from the manufacturer account for my trucks weight when they don't know what vehicle their tire is going on? Am only looking to learn TAte
 

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Because the "crowning pressure" doesn't change whether the tire has a load on it or not.

Max pressure is determined by what point the tire will crown, not what the load is.

Although I do think max load is advertised at max psi as well. Can someone confirm this?

I think my tires say 2xxx lbs at 80 psi.
 

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CSAR Bish
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Do raised truck bed caps help with better miliage? It seemed to help when I was towing my open trailer with my monster of a jeep on the back cross country, but what about while not towing like every day driving
 

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Yes, load will affect tire wear based on inflation pressure. Unloaded the rear tires need less air pressure because the tire is supporting less load. What is on the sidewall is for rated load/pressure. In some cases I'll over-inflate tires to keep temps and tread wear good.

The BFG A/T's I've got on my toy hauling truck are D tires and are 50 or 55psi on the side wall. To keep the tire temperature safe I have to run the rears at 65-70psi and I run the fronts around 60-65psi. This give the best tread life as well. If I run less pressure the tire gets far too hot and the tread wears on the outsides.
 

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Discussion Starter #19
XTremXJ asked:
"...but what about while not towing like every day driving"

Dave says;
For non-towing driving, a flat backed cap, whether flush top or raised, is the kiss of death aerodynamically. They make your truck the aero equivalent of an Excursion or van - a self-propelled brick. If you are towing they give you some scope for smoothing out your trailer, but for running down the road unhooked...frankly they suck.
 

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CSAR Bish
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gotcha, while having a load it helps to broaden or smooth out the transition of the angle of aerodynamics but when empty is will cause turbulance acting in drag on the rear of the truck.. By removing the cap, the force of the low pressure on the top of the truck plumets after the cab into the bed creating a soft buffer and exiting after the tail gate to a smaller area of void creating a smaller portion of drag.. Smaller Void, less drag.. Dammit Ive incorperated aerospace science into my everyday life, what can I say I fly and its my job, but I usually leave the thinking at work
 
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