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Old 10-09-2012, 01:59 PM   #1
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2" BB lift with 31's or 33's with a 4cyl?

I am picking up my 98 SE 4cyl next week. It has 30" BFG on there now. I am not sure which aftermarket rims are on there but there black steel. I am thinking that I will need tires soon so I want to know if the comination of adding a 2" lift and going up in tire size would be to much for the 2.5? I am ok with the performance now. I think once I add the lift it will look kinda weird with the 30" s on there. Not sure 32's would be available wouldnt they be a speacial order?

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Old 10-09-2012, 02:00 PM   #2
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You can get 32s but if it were me I'd stick with 31s.

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Old 10-09-2012, 02:01 PM   #3
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Quote:
Originally Posted by cedar
I am picking up my 98 SE 4cyl next week. It has 30" BFG on there now. I am not sure which aftermarket rims are on there but there black steel. I am thinking that I will need tires soon so I want to know if the comination of adding a 2" lift and going up in tire size would be to much for the 2.5? I am ok with the performance now. I think once I add the lift it will look kinda weird with the 30" s on there. Not sure 32's would be available wouldnt they be a speacial order?
Duratracs 33's actually measure closer to 32's... Might be something to think about. I'm planning on getting mine soon
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Old 10-09-2012, 02:03 PM   #4
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31's can be run with no lift with aftermarket wheels since the offset vs stock is less and pokes out the tires more. If you want to add 2" later... 31's look great with 2" lift... either coils or BB

Old pic of my TJ with 2" BB and 31's... 32's.... uh.... I wouldn't

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Old 10-09-2012, 02:31 PM   #5
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I have owned 2 TJs with the 2.5L engine & 5-speed transmission. Both had the 4.10 axle gears from the factory. I lifted both of them with a 2" budget boost, then installed 31" MT/R tires; I did not re-gear either one. In both cases, this was a good looking, good riding combination which still worked out okay on the highway.

Having said that, I wouldn't suggest going any taller than 31s with this engine/gear setup.
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Old 10-09-2012, 02:51 PM   #6
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Thanks for the reply's I think I will stay with 31's and a 2" lift.
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Old 10-09-2012, 02:55 PM   #7
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Originally Posted by TnDz TJ View Post
31's can be run with no lift with aftermarket wheels since the offset vs stock is less and pokes out the tires more. If you want to add 2" later... 31's look great with 2" lift... either coils or BB

Old pic of my TJ with 2" BB and 31's... 32's.... uh.... I wouldn't

Thanks! Nice Jeep! Are those rims 15's? which rims are they? and what rocker panel's do you have on there?
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Old 10-09-2012, 04:20 PM   #8
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Those are stock Jeep 15" rims painted black.
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Old 10-09-2012, 06:28 PM   #9
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Originally Posted by cedar View Post
Thanks! Nice Jeep! Are those rims 15's? which rims are they? and what rocker panel's do you have on there?

Thanks...Neil is right... stock 15x7's with Rustoleum Bedliner and the rockers are Rubicon Unlimited (LJ) Rockers that I cut down and fit to my TJ
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Old 10-09-2012, 06:41 PM   #10
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Originally Posted by Blsport7 View Post
Duratracs 33's actually measure closer to 32's... Might be something to think about. I'm planning on getting mine soon
so duratrac 33's would be smaller than most 33's?
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Old 10-11-2012, 07:06 AM   #11
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Quote:
Originally Posted by hmiller

so duratrac 33's would be smaller than most 33's?
Yes from what I'm told by many people
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Old 10-11-2012, 08:28 AM   #12
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This is half a 2 inch budget boost with 33x10.50x15 BFG AT's. I have the boost in the front, but not the back. The back is stock. Since this pic I added the bb to the rear also just to level it out. I get a slight rub at full turn but thats it.
It's a 4cyl 5spd with stock 4.10s. I run 65-70mph on the highway no problem and honestly, I haven't noticed much change in fuel economy.

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Old 10-11-2012, 10:02 AM   #13
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Originally Posted by Blsport7 View Post
Duratracs 33's actually measure closer to 32's... Might be something to think about. I'm planning on getting mine soon
Mine were 32 3/4" new
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Old 10-11-2012, 10:05 AM   #14
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sorry to highjack but what would be the biggest tire to run on a 4.0? I currently have 31's and want 33's.
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Old 10-12-2012, 02:10 PM   #15
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Quote:
Originally Posted by Enemy
sorry to highjack but what would be the biggest tire to run on a 4.0? I currently have 31's and want 33's.
What tires you can run depends more on gears than on the engine. Just find out what gears you have and that'll tell you for sure, but I'd guess that the 4.0 could handle 33's no problem even with the high-ish 3.21 gears.
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Old 10-12-2012, 02:47 PM   #16
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i have a 97 4 cyl with a 2 inch bb lift and 31's its a slug but not really any worse than it was with 30's go for it.
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Old 10-12-2012, 07:35 PM   #17
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Earlier in this thread I wrote:

Quote:
Originally Posted by Sherpa View Post
I wouldn't suggest going any taller than 31s with this engine/gear setup.
I offered this advice based on my own real-world experience of having run two different 2.5L 5-speed TJs with 4.10 axle gears and 31" MT/R tires. There are a number of factors going into this advice; I'm going to expound on one of them below.

Quote:
Originally Posted by hmiller View Post
so duratrac 33's would be smaller than most 33's?
It is very true that tire sizes do vary by manufacturer (and even tire model). Because of this, some feel it is important to research the exact diameter of a tire before purchasing it. While the diameter is certainly a good specification to know about a tire, it isn't the only important one--not by a long shot. As your tires get larger, their weight becomes more and more of a critical issue.

Adding weight to a vehicle is always detrimental to its performance; acceleration, fuel economy, and braking distance will all be negatively affected. However, all weight is not equal in this regard. The worst weight you can add--the weight that has the biggest impact on the three factors I just mentioned--is unsprung rotating weight... in other words, your tires and wheels.

For example, drive your Jeep with only you inside and note how quickly it accelerates to a given speed. Now throw 200 lbs of weight into the back and try it again. The time required will increase. Now remove that dead weight from the Jeep, and then install a new set of wheels and tires where each mounted wheel/tire weighs 50 pounds more than the one you removed. Perform a third acceleration test. The time required will be even longer than before despite the Jeep having the exact same curb weight in tests 2 and 3.

This is why you have to more than compensate for larger tires when you regear. I'll use my own Jeep as an example. I used to run 31" tires on my 3.73 gears, and I was happy with its acceleration and performance. I knew I'd be upgrading to 35" tires, and I'd want to regear to compensate. On paper, going from 31s to 35s is a 13% increase in diameter. To stay equal, you'd want to increase the gearing by the same amount... right? Multiplying 3.73 by 113% equals 4.21, so if I went with 4.56 gears then I would certainly be in good shape, right? That would be a gear increase of over 22%, or nearly double what the math says I require.

And yet my acceleration (and braking) are both noticeably slower than before I made my modifications. How can that be? A large part of the answer is that each 35" wheel/tire combo weighs 80 pounds. I even took weight into consideration when I bought the new wheels and tires, selecting some of the lightest 15x8 wheels I could find as well as choosing the BFG KM2 specifically because it was 7 pounds lighter (per tire) than the equivalent MT/R.

You may wonder how heavy my 31" tires were. They were mounted on Jeep factory 15x7 alloy wheels, and each mounted combo checked in at 61 pounds. But that's only 20 pounds each, you say. Yes, but all that extra weight has been added at the furthest point from the axis of rotation. This means my engine, as mighty as the 4.0L is, must struggle to get these four masses rotating every time I start moving. (And then my poor brakes must also struggle to bring this rotating mass to a halt every time I press the brake pedal.)

In short, rotating mass is a colossal pain in the patoot. Its negative effects worsen as you add weight further and further away from the axis of rotation. You would do well to keep this weight as low as possible.

Quote:
Originally Posted by bobbylx View Post
This is half a 2 inch budget boost with 33x10.50x15 BFG AT's.

It's a 4cyl 5spd with stock 4.10s. I run 65-70mph on the highway no problem
Maintaining a set speed on flat ground is not difficult; getting up to said speed (or even maintaining it on a steep hill) is where you'll see the impact of the larger tires. I know for a fact your acceleration has been affected, because I saw it when I only ran 31s.

Quote:
Originally Posted by Enemy View Post
sorry to highjack but what would be the biggest tire to run on a 4.0? I currently have 31's and want 33's.
You say your TJ is an X model, suggesting it has a Dana35 rear axle. I would suggest you not go any larger than a 33" tire on that axle, period--it simply isn't strong enough to handle it.
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Old 10-13-2012, 04:40 PM   #18
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I'm running 33x12.5x15 on 15x10 and 4" lift. Mine is 97, 4cyl with automatic, factory 3.73 gears and I cruise freeway at 65 easy. Up hills sometimes it drops to 55, but has great low end power.

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Old 10-18-2012, 02:34 PM   #19
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Quote:
Originally Posted by Sherpa View Post
Earlier in this thread I wrote:

Maintaining a set speed on flat ground is not difficult; getting up to said speed (or even maintaining it on a steep hill) is where you'll see the impact of the larger tires. I know for a fact your acceleration has been affected, because I saw it when I only ran 31s.
You are most likely correct. My disadvantage is that when I bought the Jeep it had 32x11.50's, then I went with 31's, then up to 33x10.50. Between all 3 the only difference I noticed was I like the handling of the 10.50 wide tire better, otherwise, no noticeable change.

As for speed, well, it gets me in and out of traffic and to and from work so it's not a problem for me. It accelerates well enough.
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Old 10-18-2012, 02:39 PM   #20
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I have a 98 with a 4" suspension lift running 33X12.50X15's and my 4 angry squirrels do just fine. it's no race car but i go where i want to go no problem.

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