clos0791

Hello everyone,

I have a quick question and maybe some of you have experience with this.

I have a 2015 JKU Sahara that came stock with 255 70 18 tires and wheels. I bought BFG K02's 285 70 17 and 17x9 wheels to go with it. I am really excited about my new wheels and tires. The K02's look pretty aggressive for an AT. I am not much into rock-crawling but more of a modest trail jeeper. I have also purchased a 2.5 budget boost. The difference between my stock tires and the K02's is minimal. The K02 is about 1/2 inch taller, a little over an inch thicker, sidewalls are about an inch bigger, and the circum is 2 inches longer. At 80 mph, the actual is 81.5 mph.

Do I need something like the AEV Procal to adjust my speedometer and other stuff? Is it really necessary with these modifications that I plan to make? Any advise will help me decide what to do, thank you!

Northridge4x4

It's a small enough difference you are probably OK. We do recommend a calibrator with any tire size change, as we have seen issues with shifting, ESP, and traction control. The Jeep has wheel speed sensors at all four corners, as well as a sensor in your steering wheel. It looks at the input from these, and it's possible for the computer to sense the Jeep is out of control when it's not. We have also seen issues with the Jeep shifting erratically, hanging gears, and even going into limp mode. Again, with such a minimal change it's likely you'll be fine but always better to be safe than sorry!

clos0791

Thanks for your advise! I am leaning towards just buying the Procal and get it over with. I have a feeling that if I dont, I will pay for it later down the road, LOL!!

You guys have great customer service. I recently bought JW speaker taillights and fog lights from Northridge4x4. One taillight came defective and you guys took care of it right away. The new taillight will be here tomorrow. Kudos to Meg, Thanks!!

MavisJk

I personally used the Superchips flashcal. I went with that over the AEV procal just for the fact that it has a screen and the price difference. I believe that the Superchips one has been updated recently so the prices between the AEV and Superchips ones are closer now. You could also upgrade the flashcal to the flashpaq for more tuning options.

When i changed from stock tires to 285/75 17 Nittos my average went from 15ish to around 13 mpg. After adjusting the tire size with the flashcal the average went up to 17-18 mpg. I'm pretty sure that if its for an automatic it changes the shift points to achieve this. It says it in the manual, but make sure you measure the actual mounted tire height as opposed to the advertised tire height (my tires measured to be almost exactly 33 inches but 285/75 17 should technically be closer to 34).

zstairlessone

Sorry for the hijack, but can you take a picture with them on the Jeep and a tape measure so I can see how tall they are??

bbolander

That size is typically 33.0 OD. Tire Rack has good size info charts.

jedg

They are 32.7 before mounting. On a set of factory rims on a JK they measure 31.5. That measured size will vary based on rim width and weight of vehicle.

zstairlessone

Thanks, my 34" tires measure at 33-1/4 on rims on the Jeep. I want to go from my KM2s to KO2s but not by losing tire size, and 285 is the widest I see in my future.

fishtailer

I made the same mod as clos0791 --> 285/70/17 BFG KO2s. When I measured the diameter at 30 psi, it was 31.5 inches even though it calcs to 32.7. Somewhat disappointed in the lack of 33" height but I am consoled like the bossy look and strong recommendation on these tires by several others on JK Forum. Additionally, the tire guys really emphasize the durability of the sidewalls on the tires vs the lower priced General Grabbers I was also considering.
Perhaps the diameter will be more at higher psi, but i want the softer ride.
Unfortunate that BFG does not make a 285/75/17 KO2. Hmmm: wonder why?

bbolander

Tire Rack shows a BFG KM2 in 285/75/17. 33.9" OD