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Tire size and fuel mileage
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=55772
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Author:  kccrd [ Tue Sep 21, 2010 8:51 pm ]
Post subject:  Tire size and fuel mileage

How many of you are running 215/85/16s and how do you like the E load range?

Author:  onthehunt [ Tue Sep 21, 2010 9:34 pm ]
Post subject:  Re: Tire size and fuel mileage

E-range sucks for mileage and ride. It was also all I could find in this size. There are a few d load range tires in this size, but I don't believe it would make a difference.

Author:  CRD Joe [ Tue Sep 21, 2010 10:27 pm ]
Post subject:  Re: Tire size and fuel mileage

Why would the load range such for either?

Author:  geordi [ Wed Sep 22, 2010 1:51 am ]
Post subject:  Re: Tire size and fuel mileage

Stronger tire = thicker rubber = heavier tire = stiffer sidewalls.

He has a point, if you are looking for a wallowing car-like ride... Why'd you buy a Jeep in the first place? There are Load Range D tires available in that size, the BF Goodrich Commercial T/A TRACTION is a strong mud / snow tread that is in a D. Interesting observation however - Side-by-side with my previous tires, the BFG Commercial T/A in a Highway tread and LRE, the tractions look a LOT wider. Like almost 235 width, yet they are still the 215.

At the same shop, at the same time I was getting the Tractions put on, they had a stack of 215/85/15 Goodyear LT tires in (IIRC) an LRE. Those looked like pizza cutters, NARROWER than the highway tread tires, yet all were the same size!

I will say that I feel like I'm getting a SOLID and honest 26mpg out of these tractions, where I was lower with the LRE tires. Ride quality... My family still moans about the ride on surface streets with bumps, but on the highway these ride better than the highway tread (at 60psi for both) and the family is happier. They tend to prefer the car-like (wallowing) ride of the Mercury Mariner hybrid tho, with the KJ's stock size tires on that. I hate those seats however - make my legs hurt.

Taller tires are better for mileage on the highway, at the expense of a tiny amount of acceleration quickness. Ride quality is a function of the stiffness of the tire and the air pressure. DO NOT RUN ANY LRD or LRE TIRE AT THE "DOOR STICKER" AIR PRESSURE!!!!!! That pressure is ONLY for the stock size and stock brand, and UNSAFE if you upgrade to a larger / stronger tire. Too little air in a larger tire (like 80psi max, only filled to 35) will cause excessive sidewall flex, and unpredictable flex / wallowing in turns. It could even cause a rollover in a sudden turn that would not have happened at a higher pressure.

You have to do your own experimentation, but I suggest rocking your hand from the 11 o'clock to the 1 o'clock position on the steering wheel while driving at about 20mph with your tires. Get the feel to a point where you can no longer feel the KJ "lag" behind your movements (because the body is still compressing into the tire while you reverse your turn) and see where the pressure is at. If the KJ feels like it is on rails and doing EXACTLY what you command - Thats a good spot. For my brand and size, the highway tread LRE were ok anywhere between 50 and 80psi - I ran them higher when towing heavy. Below 50, the handling started to really feel mushy. The Traction tires are softer, They are max at 60psi, and also feel mushy below about 45psi. I run those now at about 55psi.

As always... Your Mileage May Vary.

Author:  CATCRD [ Wed Sep 22, 2010 5:08 pm ]
Post subject:  Re: Tire size and fuel mileage

I run the 215/85s in a not-so-aggressive all-terrain pattern. They are load range D and I run them at about 40psi with a 65psi sidewall max. I can still get upper 20s as far as mpg, and on a pure highway trip can hit 30.

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