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4 Wheel Drive/SUVs/wheel backspacing?

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Expert: - 7/7/2006


Question
I have a 04 Wrangler "X" with the stock aluminum 15-7" wheels.  I am wanting to raise it just a bit and put on bigger wheels and tires.  I have picked out some 15-8" wheels and a 2" lift.  I am wanting the "wider" look instead of the "higher".  What is the widest tire that I can use and still have full steering range?  I would like to use 31-12.50.  If I go that wide will I have to worry about wheel backspacing and if so how much?

Answer
Greg,

The amount of lift you need, will be determined by the size of the tire you want to run.  I never recommend a body lift, as they tend to alter the handling characteristics of the suspension.  A true suspension lift is much better, as they are much more stable than a body lift.  I know a couple of people that run 31" tires on their stock TJ's with few problems.  This can depend on how tough the trails are that you plan on running.

Every vehicle has different requirements for the larger tires, such as the lift size, will you need to modify/cut out the fender flares, etc.  Due to this,  I would suggest that you purchase a few off-road magazines, and contact some of the distributors of lift kits.  They can advise you as to what size lift you would need to install the size tires you want.  Normally, with that wide of a tire, a 3.5" to 4" offset is fairly common.  If you want the wider look, you can go with a 10" tire instead of the 8".  I prefer the 8" for the tougher trails, since you can go with a little less air pressure, and the tires tend to protect the wheel a little more.

Here is a web site for you to check out.  I don't agree with everything they say, but this is a good place to start.

http://www.jeeptech.com/tire/

Carl  

4 Wheel Drive/SUVs

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Carl Brandt

Expertise

Will discuss suspensions, lifts, lockers along with tire suggestions. Trail ratings and possible requirements needed for specific type of trails. Safety equipment and what you should carry with you. Certified off-road instructor. I am not a mechanic, and 4-Wheeling is a hobby, so if I can't answer a technical question it is due to my mechanical knowledge being related to vehicles that I have owned, or have worked on. I do not have manuals on all vehicles.

Experience

40 plus years of 4 wheeling in a variety of vehicles. At the present time, my major off-road rig is a 94 Jeep Wrangler with a spring over and a 1 1/2" suspension lift. This gives me a total lift of 7" or so. I have lockers front and rear. I have removed the track bars, and sway bar for maximum articulation. I am running a stock 2.5 ltr 4 cylinder with a Jacobs ignition along with a cold air high flow filter. It has 4.56:1 gears with a Dodge NV4500 transmission along with a 3.8:1 Atlas II transfer case. This gives me a final ratio of 105:1 in low gear/low range. Other vehicles I own, are a 96 Ford F-250 with a 6" lift, posi rear end, 36" Hummer tires, 5 speed with a fuel injected 460 ci engine, an 87 Samurai with an 8" lift, Ford 9" rear end with a spool, Chevy Dana 44 front end with an electric locker, 5.88 gears, 16% reduction in high range and a 6.5:1 low range with 35" Baja Claws, and a stock 2003 Grand Cherokee Overland. Trails I have run are the Rubicon (10 times), Dusey Ershim, Fordyce Creek trail, McGrew trail, several trails in Moab, Utah along with local monthly runs.

Organizations
Lost Coast 4x4's Cal 4-Wheel Corva UFWDA Blue Ribbon Coalition

Education/Credentials
Certified off-road instructor - Certificates in engineering/electronics

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