205 or 225s

Sub 2500lb fwd, w/ limited slip, no power steering, current power output around 140 to the wheels, coilovers with adjustable top hats on the front. 

Wheels are tires will only be utilized to autocross on. Tires are planned to be CR-1s. The current OE wheels can run 205s or if I drop $600 I can get lighter aftermarket wheels that would accommodate either 205s or 225s (205/50R15 or 225/45R15). Due to gearing 3rd will likely be needed regardless and the gearbox and linkage is very willing to shift back into 1st as needed. 

How wide of a wheel are you currently using? I think if its between 6in to 8in, you'll be fine with the 205/50/15s vs trying to pinch a 225/45/15

Current wheels are 5.5"

I'd be getting 7.5" wide if I opt to go 225 

A 225 on a 7.5 is still going to be a little pinched.  I switched from 225 ra1's to 205's when I used to road race a 1st gen MR2 on 15x7 wheels and picked up almost a second a lap.

Unless you go to an 8 inch wide wheel I would stick with a 205.

I haven't messed with CR-1s, but I agree with 205 unless you can go to 8" or wider.

Don't do a pinch. 205s should be fine. It's easy to think that wider is always better when it really isn't (I've made that mistake). Heavier unsprung weight, greater drag and rolling resistance at a higher cost isn't always the best choice at your power output level. Good luck!

Check the actual tread width specs on the tires you're looking at, you'll be surprised how much they vary.  For instance the tread width of a 225 RS-4 is almost identical to the tread width of a 205 RE-71R.  But in either case I agree with the other posters- I wouldn't put a 225 on anything narrower than 8".

pimpm3 (Forum Supporter) said:

A 225 on a 7.5 is still going to be a little pinched.  I switched from 225 ra1's to 205's when I used to road race a 1st gen MR2 on 15x7 wheels and picked up almost a second a lap.

Unless you go to an 8 inch wide wheel I would stick with a 205.

I suspect that was the same thing that some Miatas found - the extra rolling/aero drag of the fatter rubber didn't pay off in cornering speeds and you were giving the sidewalls better support with a 205 on a 7 like you said.

But autox? I'd be going as fat as possible. You're going to have a harder time managing traction than worrying about drag.