Tires and wheels - how does changing size affect handling?

Hi all,

I am new to Jeeps and just bought the one you see as my avitar. It is a 2012 Sport.

My question is how changing to smaller wheels/tires would affect handling.

The Jeep is lifted I am sure, but I don't know how much. The wheels are American Eagles and are 9" or so. The tires are 33x12.50R20.

If I go back to original size it looks like the Jeep will sit about 2" lower (almost 4" difference in tire diameter). Original size would be about 3 1/2" narrower than the ones on it now.

I see that I should be getting about 10% better MPG since the rotations per mile is lower with the bigger tires (tiresize.com/comparison).

What is your opinion? Would I get better handling if I went to something closer to original? Would you keep what I have or change?

Thanks for your opinions!
Jim

 

@Arizona Jim IMO run the 33s for better overall usage. They are only sightly larger than OEM and with a simple programmer the CPU can be programmed if not already for the tire size for optimum performance, economy and shift points.

 

According to this, they are a fair amount different (at least IMO). Not that I mind better MPG.

I appreciate your take on keeping them. I like the look for sure, and don't really want to go through getting new wheels and tires and then selling the ones that I have on it. The tires are brand new.

Jim

 

That is a great chart that aggrex posted. The speedometer error does show quite a bit of difference, hopefully you have a calibrated speedo. Although, the stopping distance is increased quite a bit with a larger tire, can make your transmission run hotter, plus it is harder on your brakes. A larger brake booster will help stopping distance, but just keep your eyes open and your fingers crossed and you will be fine. After all your Jeep was not designed for that size tire. I run 33s on my CJ7 and have noticed all the issues.

 

@Arizona Jim ....missed the part about the 20" tires while reading at work+working. For stock to small lifts (2-3") a conservative upgrade would be 32"-to-33" and 34-35" at the upper end. If economy is your goal then the OEM 225/75R16 are the way to go along with the lower center of gravity for handling but for better results off-road I want the lift and larger tires. Not a fan of the 20" for various reasons for example 17" wheels have a better selection of tires and the larger sidewall pays dividends when traversing trails. Based off your avatar pic your JK will look somewhat funny running smaller OEM size tires due to the lift that is already installed. One thing to watch out for is the weight of your heavy spare tire on the tail gate. The OEM tailgate+hinge are rated for approx 85-90lb.

***this is the 33" tires I had in mind when I was supposed to be working at work. Same speedo error but the programmer can correct this minor issue.

 

Where do I find a programmer to re-calibrate the speedo? Thx

 

Currently two of the popular units that do more than speedo correction are AEV Procal and Flashcal (available from various jeep accessory venders). I'm looking into the inexpensive newbie: OBD jscan that's cheaper and does more for less.

http://jscan.net/

 

I'm still looking into what @aggrex posted up. The jscan app. But I use the Fascal Superchip. And have had awesome results with it.
https://www.quadratec.com/products/17609_5131.htm

 

Early 2019 a buzz in the jeep community started going nuts about JSCAN. Reviewers are finding same or better functionality over AEV Procal+Flashcal SC etc for a fraction of the cost

 

Check out this Jscan video: https://www.youtube.com/watch?v=BRA6blYbcMY

 

Bought this Bluetooth OBD reader off Amazon to work with the JSCAN

$32 Vgate iCar Pro Bluetooth 4.0 (BLE) OBD2 Fault Code Reader OBDII Code Scanner Car Check Engine Light for iOS/Android

https://www.amazon.com/gp/product/B06XGB4873/ref=as_li_tl?ie=UTF8