Sti stock size is 225 45 17.

Would there be any benefit going to a 235 35 18 vs a 235 40 18? Or vice versa?

The 35 would be closer to actual speedometer speed and ground clearance would be .2 inches lower versus .6 inches lower for the 40.

Color me ig'nert.

Thanks.

 

I would ask: why not a 245?

My answer to your question would be to get the 40 series on a 235 size. Will protect the rim a little better and give a slightly better ride. Depends what you are using the tires for..

 

I agree with MugenR. I went from the stock 55 to a 40 and it was a night and day difference in ride quality. The 45 to 35 would be insane! I know someone with a 35 series and he comments on how he has to avoid railroad tracks all the time.

Your stock side wall is about 2 inches. The 235/35 would drop to 1.6 inches! A 245/40 would stay at 1.9 inches. Although overall height would increase, the ride quality should not change much.

 

Will 245/40's fit on the WRX as well? And do you know what the biggest tire that will fit on the stock rims?

 

I have seen 255/40's on WRX's, but they rolled the fender I believe. I think 215 will fit the stock. You can check NASIOC, I think someone is running 225 on the stock WRX wheel.