45 psi ?
JK Junkie
Joined: Nov 2009
Posts: 2,737
Likes: 1
From: Rochester, NY
At 40psi, my duratracs bounce all over the highway. There have been times where my rear end actually bounced sideways on the highway. Gas mileage was about 16.8 highway with wind. I dropped the pressure down to 33psi (my usual pressure) and the ride is much better! And my highway mpg went up to 17.8. I think the increased pressure is not really needed for a tire with a stiffer sidewall and higher load rating, since the tire doesn't really "shrink" with a minimal change in pressure. I can run 28 psi and the tire looks the same as it does at 40psi.
JK Enthusiast
Joined: Feb 2009
Posts: 186
Likes: 0
From: Western New York
I run my Load Range D BFG A/T's at 40 and the mpg's are 17-17.5 on the dash. I did a chalk test at 40 psi and mine look good. I tried them @ 33 and the mileage on the dash said 16. Also dependent on how much stuff you carry or tow.
Thread Starter
JK Newbie
Joined: Feb 2011
Posts: 45
Likes: 0
From: Seabrook, TX
I did do the chalk test at 40psi and did notice the outter lugs did have as much contact as the rest of the tire.
Thread Starter
JK Newbie
Joined: Feb 2011
Posts: 45
Likes: 0
From: Seabrook, TX
I usually run mine at 40psi on the road in my stock 2-door 6 speed. Recently, after a day of wheeling I only aired them back up to 35psi as I couldn't be bothered waiting for my slow ass compressor to do it's job. On the 100-odd mile trip back home the difference was very noticeable. The ride was certainly a bit softer & less bouncy, but I found I was downchanging more frequently on hills and to overtake and having to use more gas pedal just to maintain speed on the flat, let alone on hills. I calculated a loss of about 4-5 MPG running 35psi at 70MPH over 40psi at the same speed.
So higher psi's certainly make a noticeable difference to performance and mileage. At 40psi my tires always wear evenly and that's on a light stock 2-door, so 45 shouldn't affect the wear pattern too much though the ride may be as bouncy as all hell compared to what you're used to on 35psi.
So higher psi's certainly make a noticeable difference to performance and mileage. At 40psi my tires always wear evenly and that's on a light stock 2-door, so 45 shouldn't affect the wear pattern too much though the ride may be as bouncy as all hell compared to what you're used to on 35psi.
JK Enthusiast
Joined: Mar 2010
Posts: 133
Likes: 0
From: Miami, FL
You're taking some really unnecessary risks with your life (and any passengers lives as well) by running with overinflated tires.
Your traction (specifically wet weather), steering, cornering, braking/ABS will all behave a lot differently without the recommended amount of tread on the ground due to overinflation.
Also, if you were in an accident you could automatically be at fault in many states if its determined that you are running an unsafe 'configuration' on your vehicle. All the accident investigator or the insurance companies have to do is check and then state that it may have contributed.
Your traction (specifically wet weather), steering, cornering, braking/ABS will all behave a lot differently without the recommended amount of tread on the ground due to overinflation.
Also, if you were in an accident you could automatically be at fault in many states if its determined that you are running an unsafe 'configuration' on your vehicle. All the accident investigator or the insurance companies have to do is check and then state that it may have contributed.
Last edited by mattonline; Apr 12, 2011 at 12:14 PM.
JK Enthusiast
Joined: Jan 2011
Posts: 309
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From: Athens,Greece
45 psi is way to much, even 40 psi is unacceptable IMO. I run my 315/70/17s BFGs ATs at 30 psi and I am very happy with the way the car behaves on road. I used to run them at 34 psi but man what a big difference now. Moreover dont overfilled tires damage other suspension components?like ball joints? I don't think is worth the extra mpgs.
JK Enthusiast
Joined: Jun 2010
Posts: 378
Likes: 0
From: Ottawa ON
Tire to road contact is important, over inflating is dumb. Under inflating should be reserved for the trail. Off road or multi terrain style tires have huge lugs on them already and make the tire footprint that much smaller taking away grip.
JK Freak
Joined: Jan 2011
Posts: 658
Likes: 0
From: Alexandria, VA
Tire manufacturers generally recommend a PSI lower than what is ideal for optimal tire wear. This is done for at least a few reasons: 1.) softer ride; 2.) erring on the side of safety; and 3.) profit.