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Old 10-23-2009, 07:43 AM   #1
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Question Newbie TJ Tire/Wheel/Gear Questions

Hello Everyone,

I'm new to the forum and have a few questions that I'm sure you experts can help answer.

I recently bought a 2005 Wrangler SE, I-6, auto trans. all stock, with the stock steel wheels and well-worn 215/75R15's. I am considering buying Black Rock 15x8 black steel wheels and BFG A/Ts in 30x9.5x15. Primary use is on-pavement, Chicago winters and light trail use. Since my wife and daughter will also be using the Jeep, a lift kit is out of the question for now.

My questions:

Will this tire/wheel combo fit well and look good? What are the backspacing requirements? Do I need to change the speedo gear? Do I need to change anything with the other transmission/axle gears?

Also, if anyone can recommend a reputable and knowledgeable Jeep/4x4 garage in the N. Illinois area (Lake County), that'd be great.

Thanks in advance!

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Old 10-23-2009, 07:50 AM   #2
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Do you want only bigger tires or also a lift kit?

With the stock suspensions 31x10.5x15 tires look good. If you want them on the stock rims I would install additional wheel spacers.
IMO you have to change the speedo gear.

You should have 3.07 gears in your axle. The TJ will become a bit slower with 31" tires but IMO that´s still ok.
Take a look an your diff cover in the rear. On one of the bolts should be a little metal plate. on that you can read which gears you have.




Btw. welcome to WF !

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Old 10-23-2009, 02:25 PM   #3
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Quote:
Originally Posted by nitzel2572 View Post
Hello Everyone,

I'm new to the forum and have a few questions that I'm sure you experts can help answer.

I recently bought a 2005 Wrangler SE, I-6, auto trans. all stock, with the stock steel wheels and well-worn 215/75R15's. I am considering buying Black Rock 15x8 black steel wheels and BFG A/Ts in 30x9.5x15. Primary use is on-pavement, Chicago winters and light trail use. Since my wife and daughter will also be using the Jeep, a lift kit is out of the question for now.

My questions:

Will this tire/wheel combo fit well and look good? What are the backspacing requirements? Do I need to change the speedo gear? Do I need to change anything with the other transmission/axle gears?

Also, if anyone can recommend a reputable and knowledgeable Jeep/4x4 garage in the N. Illinois area (Lake County), that'd be great.

Thanks in advance!
The rims will be too wide for the tires. From what I've learn (from this forum and from the experience of friends that are attending different competitions), for 9.5, you need maximum 7'' wide rims. Even for 10.5, there is the risk of having the tires unseated, when wheeling, with 8" rims.
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Old 10-25-2009, 02:35 AM   #4
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The rims will be too wide for the tires. From what I've learn (from this forum and from the experience of friends that are attending different competitions), for 9.5, you need maximum 7'' wide rims. Even for 10.5, there is the risk of having the tires unseated, when wheeling, with 8" rims.
Not necessarily . Sports came from the factory with 30x9.50s (which never really measured out to 9.50...more like 8.7 or close to that) on 15x8 inch alloy wheels. Why would they come from the factory with that if they have a greater risk of being unseated? I have 31x10.50s on my 15x8s right now..no problems...never had problem airing down on 30.9.50s either on those same 15x8 inch rims. Don't go by hearsay go by personal experience, not someone elses. Yeah, your friend unseated in a competition...do you think the OP is gonna be doing hardcore rock-crawling? Primary pavement and even for mild to moderate or semi difficult offroading..15x8s from a 9.50 inch wide to a 12.50 inch wide will work just fine.

OP: 15x8s will be just fine. And if you EVER go to bigger tires you can go up to a 12.50 inch wide tire with no problems.
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Old 10-25-2009, 05:48 PM   #5
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20sport06, thanks much for the common sense advice. Additional questions: I'm looking at a set of Black Rock 15x8 steelies. They offer backspacing in 4.25" and 4.75". Which BS would be best for 30x9.5x15 and for 31x10.5x15 (I still haven't decided on tire size yet)??? As a reminder I have a stock suspension 2005 TJ.
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Old 10-25-2009, 06:35 PM   #6
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Originally Posted by nitzel2572 View Post
20sport06, thanks much for the common sense advice. Additional questions: I'm looking at a set of Black Rock 15x8 steelies. They offer backspacing in 4.25" and 4.75". Which BS would be best for 30x9.5x15 and for 31x10.5x15 (I still haven't decided on tire size yet)??? As a reminder I have a stock suspension 2005 TJ.
I ran 4 inch bs on my 30x9.50s because i liked the wider stance that they gave with them and now the stance on my 31s. Go with either of those...if you ever plan on going bigger than 31s get 4.25 if not then just go with 4.75
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Old 10-25-2009, 06:40 PM   #7
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How much wider were the 4"? Did you have to extend your fenders as well?
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Old 10-25-2009, 08:34 PM   #8
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How much wider were the 4"? Did you have to extend your fenders as well?
well technically...in maryland the tires HAVE to be covered but idk about illinois..but my 9.50s stuck out a lil less than an inch. and my 10.50s stick out about an inch or so.

Think of it this way. Your stock backspacing is 5.5 inches. If you go to 4.75 or 4.25 you will be pushing the tire out 1.25" more with 4.25 inch backspacing and 0.75" more with 4.75 inch backspacing.

heres my 31x10.50 with 4 inch backspacing. (use back tire for reference)



here it is with 30.9.50 with 4 inch backspacing *use front tire*
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Old 10-26-2009, 07:35 AM   #9
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well technically...in maryland the tires HAVE to be covered but idk about illinois..but my 9.50s stuck out a lil less than an inch. and my 10.50s stick out about an inch or so.

Think of it this way. Your stock backspacing is 5.5 inches. If you go to 4.75 or 4.25 you will be pushing the tire out 1.25" more with 4.25 inch backspacing and 0.75" more with 4.75 inch backspacing.

heres my 31x10.50 with 4 inch backspacing. (use back tire for reference)



here it is with 30.9.50 with 4 inch backspacing *use front tire*
Thanks again - that was very helpful!!!
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Old 10-26-2009, 08:40 AM   #10
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No problem. With 3.07 gears 31s won't be horrible but you will probably notice a lil difference and how the Jeep accelerates.

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