Does anyone know if anyone carries KUMHO's on island? I'm looking at buying a set of rears for the car and was going to get the same that I have now. I was also wondering if the setup that was on my car was correct.

The fronts: 225\45ZR17 91Y $135
The rears: 255\40ZR17 94Y $144 (They don't even have the tire in 40)

Should the tires both be either 45 or 40? I would rather go with 45 for both but wasn't sure if the previous owner did that for a reason.