Regearing a Sahara

clos0791

New member
Hey guys, I will be installing 285 65 18 bf K02s on my new 2015 jk Sahara with a 2.5 in lift. Do I need any regearing done? I'm using Fuel 18in wheels. Will my jk still ride the same? Mileage? Etc.

Thanks for any info, much appreciated.
 

wayoflife

Administrator
Staff member
It'll really depends on what gears you have. If your Sahara came with 3.73 gears, you can get by with them but if it came with 3.21's, you'll want to regear to a higher ratio. Either way, you will need something like an AEV ProCal or Superchips Flashcal to recalibrate your speedometer. MPG will definitely go down a bit - just nature of the beast.
 

mad dog 21

New member
If I remember correctly those should only be 33" tires and won't really affect anything. Like said above " check what gears you have". You should be running 3.73 gears in a Sahara model. Also, you shouldn't have to recalibrate your speedo because the difference is so minute.
 

swampdog

New member
If I remember correctly those should only be 33" tires and won't really affect anything. Like said above " check what gears you have". You should be running 3.73 gears in a Sahara model. Also, you shouldn't have to recalibrate your speedo because the difference is so minute.

Most Saharas with the 3.6 actually are built with the 3.21 gears, at least all the ones that I ride with are / were.
 

lidless07X

Member
If the new tires are load range E you will definitely notice a difference in ride just due to the heavier duty tires. E range tires are typically used on F250/350 2500/3500 trucks.

I sold off my factory 18's and went down in wheel size because tire choices were limited and expensive on 18's. If you shop wisely and sell your factory tires and wheels, you can almost pay for an entire set of tires,wheels, sensors, and shipping for the same as just getting 18" tires.

As far as gearing, it depends on what you currently have. My Sahara came with the 3:73 option but very few Saharas have them. You most likely have 3:21.
 

wayoflife

Administrator
Staff member
If I remember correctly those should only be 33" tires and won't really affect anything. Like said above " check what gears you have". You should be running 3.73 gears in a Sahara model. Also, you shouldn't have to recalibrate your speedo because the difference is so minute.

Not exactly accurate info here. A true 33x12.50 will have an actual measurement that is about 31" tall. A 285/65R18 will have an actual measurement that's taller than that so, while it may not be significant enough to really matter, there WILL be a noticeable loss in power especially if he's running 3.21 gears. As far as his speedo goes, I totally disagree and would say that he SHOULD recalibrate it as the difference WILL BE enough over his stock tires to make it off by about 3-4 MPH. This could be enough to effect his shift points.
 

IBeHeWhoIsJoshua

New member
Hey guys, I will be installing 285 65 18 bf K02s on my new 2015 jk Sahara with a 2.5 in lift. Do I need any regearing done? I'm using Fuel 18in wheels. Will my jk still ride the same? Mileage? Etc.

Thanks for any info, much appreciated.

Not exactly accurate info here. A true 33x12.50 will have an actual measurement that is about 31" tall. A 285/65R18 will have an actual measurement that's taller than that so, while it may not be significant enough to really matter, there WILL be a noticeable loss in power especially if he's running 3.21 gears. As far as his speedo goes, I totally disagree and would say that he SHOULD recalibrate it as the difference WILL BE enough over his stock tires to make it off by about 3-4 MPH. This could be enough to effect his shift points.

From my unfortunate experience with 3.21's, some sort of tuner and actually measuring the tire makes a MASSIVE difference in the drive ability. I had the street crawler stock tires, Rubicon take-offs, 35" Nittos, and now 37" Toyos. Nothin quick about her but she can keep up with normal traffic. I really wish re-gearing the way I want was in my financial ability. But, even going to 285/65R18, do yourself a favor and measure the tire installed and tune accordingly. That will at least buy you time to decide whether you want to stick with that tire size and or save for re-gearing.
 

CarolinaDozer

New member
I ran a BFG KO LT285/70R17E for years on mine with no issues on stock 3.21 gears. the milage will suffer but the pentastar has the power. I would at least do a reset to the learn values with a good scanner thats all I did with mine using my Modis. The speedometer on mine really didn't change though, only by a mile or two. I took it past one of those radar speed checks every day for a month on my way to work and they were almost spot on. So? But regardless for what a procal costs thats what i should have done for all the other advantages. When your a tech and your cheap and the Modis is staring you in the face. :bleh:
 

clos0791

New member
If I remember correctly those should only be 33" tires and won't really affect anything. Like said above " check what gears you have". You should be running 3.73 gears in a Sahara model. Also, you shouldn't have to recalibrate your speedo because the difference is so minute.

Thanks for the feedback, I just checked my sticker and under my optional equipment, it says 3.73 front/rear axle ratios. It comes with the max tow package which I have. I am now assuming that I do have the 3.73, what a relief!. I think many Saharas come with the 3.21 as standard equipment without the max tow package.
 

clos0791

New member
It'll really depends on what gears you have. If your Sahara came with 3.73 gears, you can get by with them but if it came with 3.21's, you'll want to regear to a higher ratio. Either way, you will need something like an AEV ProCal or Superchips Flashcal to recalibrate your speedometer. MPG will definitely go down a bit - just nature of the beast.

Thanks so much for taking the time to respond. I'm a new JK owner, but had a 98 sport in the past. My Sahara came with the 3.73 gear option. I am happy that I don't have to regear with my new tires. If you don't mind, what is the easiest way to recalibrate my speedometer? Is The AEV Pro Cal or Superchips Flashcal expensive? Can I do it myself? Do I recalibrate after installing the new tires? Thanks again Eddie!
 

JoeB-JKURX

New member
I've not tried a Flashcal nor have I seen one used. I do, however, have a Procal and it is dead easy to use for speedo cal, TPMS settings, and shift point adjustment (if you have the auto tranny - which I do not). It also has a function to help you center your steering wheel after a lift or steering system maintenance.
 
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