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Unread 01-10-2011, 09:38 PM   #1
Mikesquared
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BFG 285/70R17 vs. 315/70R17

So i've finally saved up enough money to get new tires and rims for my 07 JK but after digging around on the forum i've got a couple concerns. It took me forever but iv'e decided on flat black Pro Comp 7069 17 x 9 rims and am now wondering what tires to get. I know i want BFG T/A KO's but have some questions about which of the two tires to get 285/70R17's (32.7 inch diameter) or 315/70R17's (34.4 inch diameter)? I have a 2.5 inch Terra Flex BB and am concerned that the 315' will still rub. Will they? I'd much rather have the 315's but have been reading all kinds of horror stories on the forum about having to re-gear and lost power and poor mileage, etc. I'm not planning to re-gear so will i be ok to run the 315's without rubbing or do i just play it safe and get the 285's?

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Unread 01-10-2011, 09:57 PM   #2
RockyClymer
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Well, you have the auto Sahara and I suspect a 3.21 gearing (maybe a 3.73 if you got the towing package) either way, if you jump to 35s, your performance will be miserable (just search this forum for examples and comments) and you would probably need to re gear to a 5.13 (see the chart in the FAQ section for recommended gearing for different tire sizes) on the other hand - with a 2.5 BB and the rims you will get (make sure you get 4.5 in backspacing) will probably not rub at all.

Unless you want to get regeared - I would stick to the 32s...just MO.
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Unread 01-10-2011, 10:04 PM   #3
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Quote:
Originally Posted by RockyClymer View Post
Well, you have the auto Sahara and I suspect a 3.21 gearing (maybe a 3.73 if you got the towing package) either way, if you jump to 35s, your performance will be miserable (just search this forum for examples and comments) and you would probably need to re gear to a 5.13 (see the chart in the FAQ section for recommended gearing for different tire sizes) on the other hand - with a 2.5 BB and the rims you will get (make sure you get 4.5 in backspacing) will probably not rub at all.

Unless you want to get regeared - I would stick to the 32s...just MO.
Agreed. Have seen a few jokers running around on 35s with 3.21's...you don't want to do it.

Edit: granted they have a manual...but you get the point
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Unread 01-10-2011, 11:49 PM   #4
dan-jeepy
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wow small gears for some good size tires. 32ish is the best if u dont want to re-gear. im in the same boat and i have decide to go with the 285 with the TF 2.5 lift. i was happy the other day off roadin' in my JK in the stock sport set-up. with lite off roadin and the highway travel i think this is best for the little v6. until i have the money for a bigger motor.
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Unread 01-11-2011, 06:08 AM   #5
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Originally Posted by dan-jeepy View Post
wow small gears for some good size tires. 32ish is the best if u dont want to re-gear. im in the same boat and i have decide to go with the 285 with the TF 2.5 lift. i was happy the other day off roadin' in my JK in the stock sport set-up. with lite off roadin and the highway travel i think this is best for the little v6. until i have the money for a bigger motor.
I've been known to bark my 35's. I don't have a supercharger or any engine mods.

To the OP, 286/70-17 is popular for those that don't regear. I ran 315/70-17 for a while with automatic and 4.10's. The longer I had that configuration, the more pissed off I got. At first, I thought this isn't so bad. As time went on, it became more aggravating and peaked when I needed to do some extremely light towing and had a hell of a time. The 5.13's are the best mod to my Jeep I have made.
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Unread 01-11-2011, 02:37 PM   #6
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Maybe just the two doors, but my '07 has 4.10 stock. Going from 32" to 32.7" is not going to make that much of a difference. My stock tires are about 10,000 miles from needing replacement and either the 285/65R18 or 305/65R18 A/T KO (Sahara wheels) is what I'm going to replace it with. My other set is the 8069 17x9 with 33x12.5R17 Nitto Mud Grapplers. Not a noticeable power difference or mpg difference. personal experience
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Unread 01-11-2011, 03:08 PM   #7
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go big you'll wish you went bigger
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Unread 01-11-2011, 06:02 PM   #8
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I have 285/70/17’s & 4.10's (Auto Trans). The power around town is pretty good, but once I hit the hills it sucks. I can't imagine what 34.4 (35's) would be like without the proper gearing. If you go with the 34.4 tires I would say that a regear is in your future as well as a proper tire carrier. If you are on a budget go with the 33's. If you think that you will regret the 33's and want 35's, start saving for gears, tire carrier, and programmer. Do it right the first time. I want 35's, but they are a lot of money to run them correctly.
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Unread 01-11-2011, 06:12 PM   #9
cbeas
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Split the difference & go with 305/65/17's. I just put these on last week & love it!!
p1030356.jpg   p1030357.jpg   p1030360.jpg  
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Unread 01-11-2011, 07:27 PM   #10
Mikesquared
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Thanks for all of the advice guys. It looks like the 285's is gonna be the way to go for now. cbeas, thanks for the pictures. My JK's black too so it's great to see what it'll look like. Now i'm super stoked to get these things put on quick! But i'm not sure what you mean by "split the difference?" The 305/65/17's are actually only 32.6 inches and list on Quadratec for $293.99? I thought stock Sahara's were on 18's? Am i wrong? My guess is you meant 305/65/18 which stand at 33.6 inches and list for $324.99. I can get the 285's installed for $277. Either way the tires look great but the Pro Comp flat black 7069 rims i want don't come in an 18. What about your spare? Gonna get a cover and keep the stock one?
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Unread 01-11-2011, 07:36 PM   #11
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Mine is an X so it has 17 inch wheels. By splitting the difference I just meant that for me I didn't want to go as tall as the 315's but I wanted wider than a 285. The 285/70/17 & 305/65/17 are within one tenth of an inch of each other in height, so that's negligible to me. I didn't want to go too tall since I have an automatic & don't want to spend the cash on regearing. This is the perfect setup for me.

As for the spare...it's on there now. I took the pictures before it came in. The place I got the tires locally had to order the 5th one.

Whatever size you go with you'll love it! I stuck with the BFG's since I ran 2 different sets on my old TJ & they never let me down. My JK drives so much better with these on!
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Unread 01-11-2011, 08:03 PM   #12
Mikesquared
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Sounds like were in the same boat regarding automatic and no re-gearing. I've only heard great things about BFG's. I do a ton of freeway driving up to my cabin in northern WI so i've been told that the more narrow 285 could be the way to go for that reason as well. Thanks again for the pics. I'll try to repay the favor when everything is mounted. I'm now so close to a done deal i can almost smell the rubber!
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Unread 01-11-2011, 08:17 PM   #13
cbeas
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What a nice smell it is too! It's crazy how excited we get over dropping so much money on rubber...It's a Jeep thing I guess! I keep going down to the basement just to look at mine!
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Unread 01-12-2011, 06:09 AM   #14
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Split the difference & go with 305/65/17's. I just put these on last week & love it!!
Breakin the bank to buy 5 tires? Whats the story with the spare?
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Unread 01-12-2011, 06:18 AM   #15
paul84043
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If you go much bigger than the 285's you'll also want to cut your pinch seam back. There's some overhead to going larger than that.
Keep in mind a set of tires is probably going to last you 3 years on average. That's time to get a feel for what you're going to do with the Jeep, and to save some cash to do it.
I don't see the downside to doing the "smaller" tires right now personally unless you've got a big old wad of cash sitting around.
Also, if you really want to know the actual tire size....don't rely on a math conversion, actually measure the tires that you're wanting to get....they vary quite a bit.

I'd also look around at more tires...the duracraps get some mixed reviews depending on your usage...some love them...some not so much. We went with a slightly more aggressive a/t with good factory siping and a center strip that keeps them very quiet.
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