Correct wheel spacer size with aftermarket rims and tires.

[freshmn101]

I'm looking to upgrade the stock 18 inch 235 wide tires on the Model 3 with 19 inch 255 tires. I'm also looking to add spacers and need your opinion on the correct size. I see most people go with 15mm in the front and 20mm in the rear but this is with the stock 235 tires. Would that size make the car look too aggressive or still be flush with 255 wide tires? Should I go with smaller spacers? Post pics if you have any for reference.