I want to make sure I won't upset the stability/traction control, since stock the Journey sedan comes with the same width wheels/tires all around.

 

RWD is much less critical regarding tire sizing, but best to keep within 3% of the OEM diameter and your front & rear diameters as close to each other as possible.
Here's a list I posted about the best tire combos for the most common wheel diameters, just need to pick the right width & offset wheels to mount the listed tires properly.
https://www.myg37.com/forums/brakes-...ml#post3992771

 

No, there's no issue. The stagger on OEM duckfeet for the RWD Sport package is 1", and I have a 1.5" stagger with my Vossens. It pretty common.

 

You seem to be a wealth of knowledge on wheels for our platform, can you recommend a proper offset for 18" Enkei RPF1's 8.5" up front and 9.5" in the rear?

 

shoot me a PM and I'll check what they have and get back to you tonight.

 

Done, thank you!

 

The 2010 sales brochure shows an option for two Sport Wheel packages for the Journey model. The first is "Split 5-spoke 18-inch aluminum alloy wheels with 225/50R18 all-season tires (AWD model)." Door number two was "Split 5-spoke 18-inch aluminum alloy wheels with 225/50R18 tires (front) and 245/45R18 tires (rear) summer performance tires (RWD model)" so apparently the factory had no problem with different size tires on the RWD models. According to the tire size calculator:

https://tiresize.com/calculator/

the difference in tire circumference between the two tire sizes on the RWD choice is 0.2 inches or 5 revs/mile. 225/50R18 has a diameter of 26.9 inches and circumference of 84.3 inches; 245/45R18 has a diameter of 26.7 inches and circumference of 83.8 inches.