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Old 02-11-2014, 04:39 PM   #1
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Auto, 3.21, and 33" - Will I regret it?

I have a 2013 JK Sport that I got as my first Jeep (one that leaks like a sieve, but that's another story). It's a DD and will probably only be used for very light off roading - the most I might get is some flat fenders to avoid rubbing and 19/60 springs for lifting - not many mods since we're going to be saving up for a house.

I bought it before I knew about the different gearing, it has a 3.21 rear. I know I have to adjust the tire size with a pro-cal (though I think my dealer can do it - they sell some bigger-wheeled wranglers on their lot).

Right now I've got the 24S package 255/75R17 Wrangler SR-A's which come in around 32" on the 17" 5-spoke wheels that I'll be ditching.

I'd like to go for some black 16x8 wheels (with appropriate backspacing to avoid rubbing) in alloy if I can find 'em to save a few lbs. along with some 285/75R16's (which would probably make up for any weight saved on alloy wheels).


Will I regret going to bigger tires like that - mileage, performance, etc. -with those gears and an automatic? Will it screw up shift points and whatnot just going to 33's?

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Old 02-11-2014, 06:06 PM   #2
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Others here can give more imput but I think running the 33s will be fine I have the 2012 with 3.21s and I run 32s no issues If you want to run bigger get a procal I think under $200 instead of having your dealer do it at that or more and you can do more than adjust your Speedo I think you can change shift points too not sure but something to check out.

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Old 02-11-2014, 06:14 PM   #3
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IMO you will be fine...of course I live in North East IN and it is pretty flat around here...but I think that the 3.21's are more than enough coupled with the Pentastar for up to maybe 34"s....assuming you change the shift points. Now let me toss a "qualifier" on that. I wouldn't want to wheel with that set up.

I say that because my TJ did fine on the street and "light" off-road with 3.73's and 33"s. But I started getting stuck, in places I never got stuck before, when I was running 31"s. and that is when I decided I had a choice no wheeling, or regear. I regeared the TJ I have the JK's for the street.
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Old 02-11-2014, 08:01 PM   #4
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I have an auto, 33's, and 3.21 gears and it's absolutely fine. I can't notice a difference between stock and the new setup in terms of performance. As for gas mileage, it's been so cold here that my mileage is crap regardless of tire setup. Also, I'm at altitude (Denver), and even so, it's still perfectly fine.
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Old 02-11-2014, 08:29 PM   #5
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I've got a 2013 2 door sport auto with 3.21 gears and 295/70/17 (33.8x12)cooper discoverer stt. I can feel a slight difference but I haven't gotten a procal yet. I haven't regretted and I don't think you will either
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Old 02-11-2014, 08:34 PM   #6
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I have duratracs they are 285/75/17 with xd hoss wheels. I have 3.21 gears and I noticed a pretty big deference. I think the width does not help. They measure a little under 33 inches. I know your wanting to buy tires and not be disappointed I was in the same place. With that being said If I could go back I would have regeared and put 35"s on it. Just me though good luck
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Old 02-11-2014, 09:57 PM   #7
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I just bought a 2014 JKUS with the 3.21 gears. I was hesitant at first with a lift and bigger tires. I liked my stock ride. Very smooth, so I went with the budget booster lift or (coil spacers) 2 1/2 and the pro comp 33x12.50x17. I also wanted to keep the lift small to be able to easily fit in garage. I will say there is a slight loss of power but not as much as you think ( they're not made for speed). The mileage? Yeah 1-2 mpg less. Overall it is very worth it, jeep looks awesome now.
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Old 02-11-2014, 10:09 PM   #8
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I have a 2011 JK Sport and put 33" tires on it with a 3.21 gear ratio. I notice it with the mph difference on the interstate however gas hasnt changed that much. I enjoy my 33's however some people may tell you different. I agree that they look better on a 2DR than a 4DR
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Old 02-11-2014, 10:23 PM   #9
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If you're in the mountains or hilly areas you'll notice the difference as it'll bog down a little. The 3.6 is a pretty peppy engine though.
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Old 02-11-2014, 11:31 PM   #10
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I have 3.21 and 33's, I didn't notice any difference from my stock tires. The 3.6 and auto are a good match.
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Old 02-12-2014, 07:44 AM   #11
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Quote:
Originally Posted by Joshlhicks84 View Post
I have duratracs they are 285/75/17 with xd hoss wheels. I have 3.21 gears and I noticed a pretty big deference. I think the width does not help. They measure a little under 33 inches. I know your wanting to buy tires and not be disappointed I was in the same place. With that being said If I could go back I would have regeared and put 35"s on it. Just me though good luck
Looks like the OP has a two door, you have a four door..big difference. I have a JK 2 door sport with Crager soft 8's and 33" tires and hardly notice the difference.(3:21 gears)
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Old 02-12-2014, 07:56 AM   #12
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Offroading in 4HI will be slightly affected, it will feel "heavy". I now tend to use 4LO more often.

6th gear in the highway is useless, no power whatsoever. I corrected that by installing an Intake/ Exhaust/ Bullydog tuner, gave me power I lost.

All in all, it's good.
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Old 02-12-2014, 07:57 AM   #13
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2012 2-door w/ 3:21.

I ran 33x12.5 for 2 years and had zero issues. With the 3.6 I really didn't even notice any power loss. You'll be fine.
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Old 02-12-2014, 01:24 PM   #14
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Ive got an 4dr, but Im running a 13 sport s with 3.21's auto on 35's and it has lots of power. I am running a Flashcal, much needed to change the shift points. Without it, it would hold gears to long.
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Old 02-19-2014, 09:49 AM   #15
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Thank you for starting this thread lol. I have a jk auto + 3.21 and really would like to put 33" duratracs someday. I've read countless posts and people are really all over the place in terms of opinions and I still am not sure if it's worth doing. Mpg I don't care about, it's the power loss I am cautious about. So my question is what are the true negatives of putting 33s on with 3.21 gearing. I know about all the positives lol
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Old 02-19-2014, 11:48 AM   #16
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Satisfied with factory gear ratio?

Not scientific, but this may be of some interest to you. If I recall correctly there was another poll from that time period that also considered the 4.10 gears, but I don't think I posted that poll so harder for me to find.
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Old 02-19-2014, 12:15 PM   #17
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After reading that thread I still don't have full clarity on the true pros/cons with the following: 33s + 3.21 auto on a 13' jk. It's my DD but I plan to do some light off roading.
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Old 02-19-2014, 06:56 PM   #18
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Talking

Bump. I'm not trying to beat on a dead horse, but i'd really appreciate some clarity for my expectations if I went with 33s! Thanks!
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Old 02-24-2014, 09:55 AM   #19
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OK OK OK, ONE last miracle bump. Again, not trying to keep another "3.21" thread alive, but I just want to know my limits on tire size with what gearing I have. Thank you.
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Old 02-24-2014, 10:03 AM   #20
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I had 13 with auto 4 door with 3.21 and 33's would be max for what I consider decent performance. if you live in flat land and do very little off roading maybe go bigger but from my prespective living in hilly areas the auto hunts too much even with 33's. I am much happier with 4.10's now.
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Old 02-24-2014, 10:10 AM   #21
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I know that there is tremendous flexibility with 3.73+. But I'm just trying to get an idea if I can put 33's w/ 3.21 without losing "noticeable performance". Keep in mind its a 2DR
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Old 02-24-2014, 10:11 AM   #22
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The Sport S has 32" tall tire on it to begin with with so the little increase in diameter isnt going to effect driveability much. the weight difference in tires is where it will come into play. The stock SRA's are 33lbs (claimed) to the Duratracs 285 (33) are 54lbs claimed.

Like I said earlier, Im running 35x12's on the stock 3.21 gearing and find the driveability close to stock WITH the superchips flashcal. Without it, the Jeep would almost redline before switching gears... I highly doubt you will experience much difference, if so pick up a procal or flashcal to help with the shift points
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Old 02-24-2014, 10:18 AM   #23
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The Sport S has 32" tall tire on it to begin with with so the little increase in diameter isnt going to effect driveability much. the weight difference in tires is where it will come into play. The stock SRA's are 33lbs (claimed) to the Duratracs 285 (33) are 54lbs claimed.

Like I said earlier, Im running 35x12's on the stock 3.21 gearing and find the driveability close to stock WITH the superchips flashcal. Without it, the Jeep would almost redline before switching gears... I highly doubt you will experience much difference, if so pick up a procal or flashcal to help with the shift points
So if i were to run duratracs (285) w/ a procal or flashcal, I shouldn't feel a big difference? Sorry I am a complete newbie when it comes to tires/tire sizes/flashcals etc.
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Old 02-24-2014, 10:28 AM   #24
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So if i were to run duratracs (285) w/ a procal or flashcal, I shouldn't feel a big difference? Sorry I am a complete newbie when it comes to tires/tire sizes/flashcals etc.
No worries
There shouldnt be any noticeable change at all other than the bigger grin on your face turning the new duratracs. And the hum from the tires of course lol
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Old 02-24-2014, 10:40 AM   #25
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I paired up my 3.21 Auto JKU with 32" BFG KM2 MT Rubicon takeoffs and re-calibrated with a FlashPaq. I noticed the transmission searched for gears a little more on hills, but it has improved as the PCM adapts. I don't know whether or not this is a result of larger tires, but I really have to open the throttle in reverse in order to back out of my lower driveway (steep grade), more than any other vehicles I've parked down there, including a '98 suburban.
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Old 02-24-2014, 10:47 AM   #26
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I went with 33x12.50x15 DT on my 13 with 3:21 auto. I bought the AEV flascal and it did help with shift points and corrected the speedo. Love the 33s and there was very very little difference in power . Would do it again with no regrets.
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Old 02-24-2014, 10:52 AM   #27
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I went with 33x12.50x15 DT on my 13 with 3:21 auto. I bought the AEV flascal and it did help with shift points and corrected the speedo. Love the 33s and there was very very little difference in power . Would do it again with no regrets.
Thank you for sharing your experience. Now would you consider putting a 2.5 lift on your rig or do you not think it'd be worth it?
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Old 02-24-2014, 11:03 AM   #28
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Thank you for sharing your experience. Now would you consider putting a 2.5 lift on your rig or do you not think it'd be worth it?
Are you thinking for clearance of the Duratracs or just be be higher?

Also one thing to remember, lifting anything will affect performance and mpg loss at highway speeds not only because of increased driveline strain (tires,angles of drive shafts) but because of the high volume of air being allowed under the vehicle.
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Old 02-24-2014, 11:23 AM   #29
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Are you thinking for clearance of the Duratracs or just be be higher?

Also one thing to remember, lifting anything will affect performance and mpg loss at highway speeds not only because of increased driveline strain (tires,angles of drive shafts) but because of the high volume of air being allowed under the vehicle.
Just to be higher. But I'll take it one step at a time. As long as 33s will have a minimal effect on performance, I'll be happy. I don't plan on regearing.
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Old 02-24-2014, 12:11 PM   #30
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Ahh, then lift if you want to lift. The higher than stock the better lol. I wouldnt have any worries on the 33's effecting performance.

Just make sure to post pics when their on

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