Hi all, I'm replacing my tires here in a couple of weeks due to innerwear in the rears. 2016 is300 awd, bc coils, figs lca bushings, rear spc camber arms on stock fsport wheels. So 225 40 18 fronts and 255 35 18 rears. Am I able to do 245 40 18 rears without messing up the AWD system? Someone selling a set of take-offs with 200 miles for a great price and I'd like to know if that rear will work before I dish out for all NEW store-bought tires.

 

I would not advise doing this. I would try to get something even closer to stock. Those 245's will probably be stretched on the stock wheels anyway.

 

I don’t think the 1cm width change will be a issue, but you will be close to the AWD front/rear difference that would trigger an error (IIRC, you need to stay under 3%). However, as the rear tires wear, they will get closer to the front diameter (unless your fronts are already worn, pushing you over the 3% differential) (ignore the poke and inset numbers):


You’d be better off if the profile was 35 (like the original):


You can go to willtheyfit to compare your existing fronts to the old and new rears, to see the size and speedometer differences.