I'm putting together a set of wheels and tires for SCCA solo2 STR class. The class limits rim width to 9" and tires to 255s. So after considerable research I'm fairly certain that I will be OK with 18x9 +20 rims all around and either 255/40/18 F and 255/45/18 R or 255/45/18 all around. Does anyone see any issues with either set up? Any advantage or disadvantage to the 40 - 45 set up vs. the 45 all around?

Thanks in advance!!!

 

Advantage would be compromise between rolling resistance and handling of course.
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^^^ Not sure I get this? I can see slightly less sidewall flex with the lower profile affecting handling but rolling resistance?

 

I would do the 40's front and rear. Neutral handling and shorter gearing.

 

If these were going to be AutoX only wheels and tires I'd go that way but since the budget doesn't allow for two sets right now, they are going to do double duty as daily drivers for probably longer than the life of this set of tires.

My speedometer is already a % or 2 slow so I don't really want to go another 2.4% in that direction. The 45s on the rear should make it almost dead on and from what I've been able to find the speedometers on these cars are either not adjustable or not easily adjustable. Someone correct me if I'm wrong...

The other consideration is purely asthetic. I'm only running tien h-techs, -0.5 front and -0.3 rear (it's a roadster) so I'm thinking about wheel well gap as well.

When they becomes a dedicated set of race tires I'd probably go with the 40s front and rear. For now I'm leaning toward 45s on both ends to get the neutral handling piece unless someone comes up with something I'm not thinking of.