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Discussion Starter · #1 ·
I have a fairly new 12 JK Sport S auto and so far I'm loving it. I've only offloaded a couple of times but I do plan on doing it a bit more as I get experience and learn the ropes. This Jeep is my DD and I do have a 40 mile commute each day on the highway, so I want to make sure my mileage and highway driving doesn't suffer too much. I also want it to be at least as quick, if not quicker on the road. I already have an expensive mountain biking habit so I'm not in the position to throw a ton of money into this, but I can't leave it stock...

Here is what I'm looking at:

Tires/Wheels > I'm on the stock rims and tires now. I was planning on wearing the tires out before switching but I might switch them out earlier. I'm thinking 33" Duratecs would work well. I'm unsure if I will keep the 17" stockers or go with a 15" or 16" rim. I'm concerned about how the sidewalls will feel with the smaller rim. Comments?

Lift > 2.5" Teraflex lift kit. Do I go with the Teraflex shocks or stick with the stockers?

Gearing > I believe mine comes with the 3.21 gearing. If I were to regear I'd want to go on the higher side in case I get bigger tires down the road. What gear would you recommend? What's the downside to having too much vs. too little?

Thanks in advance for any comments.
 

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Tires/Wheels > I'm on the stock rims and tires now. I was planning on wearing the tires out before switching but I might switch them out earlier. I'm thinking 33" Duratecs would work well. I'm unsure if I will keep the 17" stockers or go with a 15" or 16" rim. I'm concerned about how the sidewalls will feel with the smaller rim. Comments?
Get rid of the stockers. It'll be cheaper overall and the ride will be better, especially with 15" wheels. Here's what I did: (http://www.wranglerforum.com/f33/new-33x12-5r15-duratracs-on-black-rock-d-windows-126381.html). Here's another great option: (http://www.wranglerforum.com/f33/33x12-5r15-goodyear-duratracs-installed-pics-and-video-96568.html).

Lift > 2.5" Teraflex lift kit. Do I go with the Teraflex shocks or stick with the stockers?
I have the coil version of this lift. You'll need to get the kit with the shock extensions if you want to keep the stock shocks. If you can afford it, I'd say go with the TeraFlex shocks or get a set of better aftermarket shocks like Old Man Emu or Bilstein. I have the Old Man Emus.

Gearing > I believe mine comes with the 3.21 gearing. If I were to regear I'd want to go on the higher side in case I get bigger tires down the road. What gear would you recommend? What's the downside to having too much vs. too little?
With a 2012, you'll be fine on 33s with 3.21 gears, especially a lightweight combo like what's shown in the threads I linked above. If you go to 35" tires, you may find yourself more seriously desiring a regear.

If you do decide to regear, here's a chart to help you decide. It looks to me like 4.56 or 4.88 is the best spot to put the 3.6 for either 33s or 35s.



As for the "downside" of overgearing, I think you can see it in the chart. If you have the auto transmission for example, and you put in 5.38 gears with 33" tires, you'd be spinning nearly 3200 RPMs at 70 mph. If you were going 80 mph, your RPMs would be even higher. You'd have lots of power of course, but it would be loud, hard on your engine, and I'd expect your gas mileage would take quite a hit.

The goal with a regear is generally either to (a) return to stock numbers after adding bigger tires or (b) find the "sweet spot" in terms of engine performance. The "stock numbers" are basically in the high yellow or low green zones depending on what gear ratio you started with. The "sweet spot" for engine performance is (I would expect) probably more in the high green or low blue zones.
 

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Discussion Starter · #3 ·
Get rid of the stockers. It'll be cheaper overall and the ride will be better, especially with 15" wheels. Here's what I did: (http://www.wranglerforum.com/f33/new-33x12-5r15-duratracs-on-black-rock-d-windows-126381.html). Here's another great option: (http://www.wranglerforum.com/f33/33x12-5r15-goodyear-duratracs-installed-pics-and-video-96568.html).



I have the coil version of this lift. You'll need to get the kit with the shock extensions if you want to keep the stock shocks. If you can afford it, I'd say go with the TeraFlex shocks or get a set of better aftermarket shocks like Old Man Emu or Bilstein. I have the Old Man Emus.



With a 2012, you'll be fine on 33s with 3.21 gears, especially a lightweight combo like what's shown in the threads I linked above. If you go to 35" tires, you may find yourself more seriously desiring a regear.

If you do decide to regear, here's a chart to help you decide. It looks to me like 4.56 or 4.88 is the best spot to put the 3.6 for either 33s or 35s.



As for the "downside" of overgearing, I think you can see it in the chart. If you have the auto transmission for example, and you put in 5.38 gears with 33" tires, you'd be spinning nearly 3200 RPMs at 70 mph. If you were going 80 mph, your RPMs would be even higher. You'd have lots of power of course, but it would be loud, hard on your engine, and I'd expect your gas mileage would take quite a hit.

The goal with a regear is generally either to (a) return to stock numbers after adding bigger tires or (b) find the "sweet spot" in terms of engine performance. The "stock numbers" are basically in the high yellow or low green zones depending on what gear ratio you started with. The "sweet spot" for engine performance is (I would expect) probably more in the high green or low blue zones.
Thanks for the info. That tire/rim combo does look badass. Kinda puts the stockers to shame.

I'll have to see what the budget brings for the lift. Is a lift required to run that tire/rim combo?

I'll probably forgo the gear change. It is a ton of money for power that I'd probably forget about after the 1st month of having it.
 

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regearing will be where most of ur money will go.. all though the 2012 jk can turn the bigger tires. ur going to lose some performance moving up to a 33" tire , and if ur concern is wanting more perfomance.. then a 33" tire would not be for u , unless u did regear, and if ur going to regear i think most people would say go with the 4.10 or higher, depending how much money ur going to throw into this thing.. but a 4.10 waill be a good all around gear for most applications.. can do a 33 with plenty of performance and can do a 35 with no problems..
 

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I'll have to see what the budget brings for the lift. Is a lift required to run that tire/rim combo?
A lift won't be required to run those tires onroad, but when your suspension flexes offroad the tires will rub on the fender flares. So the answer is "sort of." You can get spacer lifts (budget boosts) pretty cheaply. Like this one. (FYI, though--I wouldn't recommend the coil lifts by that company, just the spacer lifts. Look elsewhere for coil lifts.)
 

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MTH you are getting scary good at answering this stuff. I mean you've integrated correct specs, info, pictures..etc. Now I was thinking you need to get serious and move on to a power point presentation. :popcorn:

Oh aren't you supposed to be working too? :D
 

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Gearing > I believe mine comes with the 3.21 gearing. If I were to regear I'd want to go on the higher side in case I get bigger tires down the road. What gear would you recommend? What's the downside to having too much vs. too little?

Thanks in advance for any comments.
Actually you would want to gear lower. Numerically higher numbers equate to a lower gear ratio.
 

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MTH you are getting scary good at answering this stuff. I mean you've integrated correct specs, info, pictures..etc. Now I was thinking you need to get serious and move on to a power point presentation. :popcorn:
It sure seems that way doesn't it? But we all know it's just an illusion. There are like six topics that (a) every newbie wants to know about and (b) I have sufficient knowledge to answer. The topics are often related (lift, tire size, gearing, etc.) so the answers are often synthesized together.

BUT - Outside of those topics, I'm a complete idiot. Go ahead, ask me a lighting question . . . go ahead . . . You'll get a blank stare while I wait for Hilldweller to come help.

Oh aren't you supposed to be working too? :D
Every question can be answered by saying, "It depends . . . ." :hide:

Did I mention Jeeps are more interesting than legal research? True story. :D
 

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Discussion Starter · #9 ·
A lift won't be required to run those tires onroad, but when your suspension flexes offroad the tires will rub on the fender flares. So the answer is "sort of." You can get spacer lifts (budget boosts) pretty cheaply. Like this one. (FYI, though--I wouldn't recommend the coil lifts by that company, just the spacer lifts. Look elsewhere for coil lifts.)
Remind me again so I don't have to look it up. What's the difference between the spacer and the true lift. Why is the lift better.
 

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Remind me again so I don't have to look it up. What's the difference between the spacer and the true lift. Why is the lift better.
They are both "true lifts."

There are essentially three types of lifts for a JK: (1) Body lifts, (2) spacer lifts or "budget boosts," and (3) coil or spring lifts.

Body lifts just insert spacers between the body and the frame. It creates the illusion that the jeep is higher, when in actuality the frame and undercarriage remains in the same place. Other than the illusion of height, the only benefit these offer is that they raise the fender flares along with the rest of the body, allowing you to run larger tires. But since the JK comes with 32" tires stock and can cram in 33" tires without a lift, these aren't really recommended for the JK. They also have odd side effects like shortening your shift lever as a result of the Jeep's body moving upward without taking the engine, transmission, frame, etc. with it.

Spacer lifts or "budget boosts" are spacers that you put on top of your current coil springs. They look like hockey pucks. Unlike a body lift, they will actually raise the frame further off the ground. These are commonly used in the JK. The principal downside is that your coil springs themselves aren't any longer, so you haven't increased the amount of articulation your jeep can handle. Also, since you're keeping your stock coils, the "ride" is likely to feel unchanged or at least very similar.

Coil or spring lifts actually replace your current coil springs with new, longer coil springs. The result is the same as a budget boost but you actually have longer springs. These can not only enable greater articulation, but can improve the ride quality as you can get coils that are superior to the stock coils that came on the jeep.

Coils are more expensive than "hockey pucks," and, therefore, coil lifts are more expensive than budget boosts and body lifts. The reason I recommended Rough Country's budget boost is that for the price, it's hard to beat. Sure, Rough Country is a "discount" type of manufacturer, but how fancy can you really get with hockey pucks? Their coil lifts however, have a reputation for sagging over time, so I'd avoid them. YMMV of course, I understand some folks are very pleased with their Rough Country coil lift.
 

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This Jeep is my DD and I do have a 40 mile commute each day on the highway, so I want to make sure my mileage and highway driving doesn't suffer too much.
Let's see, you want 33" tires, a 2" lift, and regearing... but you don't want to hurt your gas mileage too bad???

If you do those things, your mileage will suck. It's all a trade off, but don't have any illusion that you can do all these things and your mpg will be close to what you have now.
 

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Wow MTH you could have answered all my questions a long time ago. You are a wealth of information. Thanks for sharing.
 

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Discussion Starter · #15 ·
Let's see, you want 33" tires, a 2" lift, and regearing... but you don't want to hurt your gas mileage too bad???

If you do those things, your mileage will suck. It's all a trade off, but don't have any illusion that you can do all these things and your mpg will be close to what you have now.
What's wrong with wanting it all? :thumb:
 
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