Was at Costco asking to do just that and was told can't do just rears, must do all four. Think it's an up sell..
Car comes 225.50.18 all four sides. I asked for 245.45.18 for rears he said no,do all 4.lol I saw the tire and I'm like damnnnn that's big .... Hmmm don't wanna look stupid
Tires were Michelin pilot super sport and was given a out the door price of $952.25

Thanks guys

 

It makes no sense to run staggered sized tres on non staggered wheels. It will just keep you from rotating the tires which ends up costing you a lot more money over time. You can do it, but it's really weird. Do all 4 the same size.

 

The Pilot Super Sports are great tires summer tires. However, they aren't meant to be driven in near freezing temperatures. The don't have much grip in the cold. Trust me, I have them.

 

I'd go w/ Black Bettys' suggestion and run the 245s all around, 225s are pizza cutters, especially in back

 

True about the cold, I'm based in south Florida so cold for us is low 40's f.
Hope that won't happen too often
245's looked an inch wider than 225's, got me worried. anyone had that done before?
I'm excited about the better handling I'm gonna get though

 

Your sidewalls will flex more so I'm not sure you'll get better handling.

 

Your right, I'll call tomorrow about 235's . Thanks!

 

235s are a bit off w/ diameter compared to the 225 or 245. The 245/45/18s are only -0.66% different in diameter, the 235/50/18s are 1.45% off and the 235/45/18s are -2% different. Given the choices I'd either stick w/ 225s (I wouldn't but you could ) or the 245s.

 

Wow, this is very important to me. Much appreciated sir.
But with the sidewalls flexing on 245's .... Bout to shoot myself, feel so burnt lol

 

Omg, look what I found