Another noob wheel question request
 

I have done some tuning to my FR-S, and now I'm thinking of some new shoes for my daily driver. I was thinking of 18" wheels in a square setup to keep some of the original ride character. I was also thinking of going with a little more grip since I'm now at 200.75HP at the wheel with my tune. I was looking at going 8.5" wide. Down the road if I add FI I'll go wider t in the rear to 9.5 in a staggered setup. I'm think I like the Gram Light 57xtreme wheels, I just like the look of them. They look sporty.

So, now to my questions, Will going wider wheels reduce my MPG very much? I'm sure it will a little since there is more resistance from the grip, but is is significant? Will it make the ride significant rougher? I would also like to keep the stock ride hight. Since I'm going with a larger wheel do I need to lower it to keep the stock ride hight? Is 8.5 to wide to keep the character of a little loose in the rear? Last question, do I need to re-calibrate my Speedometer to keep it accurate?

I know some of you have great experience in this. This is my first time adding after market wheels and I just want to make sure I'm doing it right. I know some of this also depends on my tire choice and side wall on that tire. So many variables to consider, I'm a bit overwhelmed. I know there are shops out there I can consult on this. I'd just like a reality check before I walk in to a wheel shop and get fooled by a sales guy trying to just get a sale. I also want to make sure I'm making a wise choice of a wheel upgrade. I know I can add grippier tires to the stock wheels too.

Thank you in advance.

Rolling resistance drag, which weight and tires impact, isn't a big portion of the overall drag at higher speeds. You'll see a larger impact during stop and go driving than highway is what I'm saying. It really depends how grippy and heavy of a wheel and tire combo you go with. Way too many variables to definitively say how much your mpg will be impacted.

You should choose a tire size that keeps the tire circumference the same or close to the same. A 225/40-18 (637.2mm) is roughly the same diameter as a 215/45-17 (625.3mm). Bumping down to a 35 series tire would decrease the diameter to 614.7mm on the 225 width, 18" compatible tire.

This is a good tool to determine fit.

http://www.frsproject.com/tire_size.php

Remember, size varies a little with brand and model of tire. More square shoulders on a tire will leave you with less clearance.