360 performance tyre upgrade / sizing

Factory supplied;
215 – 45 X 18 fronts = 25.7” diameter
And
275 – 40 X 18 rears = 26.7” diameter

As a Porsche 911 centric guy, I’m not used to seeing tyres with such a large diameter difference.

Maybe F did it this way to build a bit of rake into the car???

If staying with these sizes, it seems the only grippy dry weather tyres available are the Bridgestone RE-11s.
I’d like to potentially change to other sizes to broaden the tyre choice.

I’m thinking of trying
225 - 40 X 18
285 - 35 X 18
Michelin PSSs

Now the questions;

1) If I go to smaller diameter tyres ~ 25.5”, (30 or 35 series) does that confuse any of the “stability management” or other ECU systems? I’m sure it would cause the speedo to read ~ 5% too fast.
2) Tell me what tyre sizes you have upgrade to and your experiences.

Thanks

Craig

 

Hey brother, me again. I went with Mich PSS 275/40 18 and 225/45 18 on my challenge wheels and they feel great with no issues a month or so in.