I just went and picked up a set of Work Emotion CR's and decided on Falken Azenis ST-115's for the rubber. I originally requested the tires to be 215/45ZR17's, but the guy at Autobac's went over my head and ordered the same tire in a 40 profile instead, saying that there may be a rubbing issue, but he wasnt sure. The Work wheels are 17x8 with a +47 offset. They are going on my GC8 STI, which currently has 17x7.5 Advan RGs with 215/45R17's, and what seems like plenty of room to spare for a slightly wider rim. I don't really care for tires that have less than a 45 profile (too little rubber), but I am more concerned about performance on the track. I can still switch the order before the tires are delivered, but before I do, I have a few questions...

1) Are there any known rubbing issues with a 17x8 rim + 215/45R17 tire combination on a GC8? (Add: This car has HKS Hipermax II Coilovers, in case you want to factor in suspension types)

2) 40 or 45 profile tires for autocross events... which would be better?

3) Will the wider rim add more understeer?

I did a forum search before posting this, and one mentioned the Work Emotion CR rims in 17x8 on a GC8, but there was no clear answer as to what tire size worked for sure. Any help would be appreciated!

 

8" wheels are awful wide for a 215/40. And, 215/40R17 is going to be pretty short. 215/45R17 is already a bit shorter than stock. That size should fit fine under your fenders. I would go back and get 215/45s or even 225/45 if they have that size, and I'm pretty sure they do. They might have minor rubbing, but I'm sure a little bit of fender roll or removing the fender lip lining in the rear would take care of it.

 

exactly what he said

 

Yeah, I was thinking pretty much the same thing. I really want to know how it will affect performance more though. All I can picture now is rims grinding on pavement during sharp, high speed turns. The Falken website says the 215 Azenis tires can fit rims up to 8" wide, so that should be ok, but I think 225s are out of the question. I'm not a big fan of mods that can't be undone, so rolling fenders is not something I would like to do to make wider tires fit. The Autobacs guy was asking about what kind of suspension I had, like there would be rubbing if I was riding on a set of lousy drop springs with cheap mushy struts or something. I tried to explain that I had HKS Hipermax II's and that they are pretty stiff on turns and bumps, but, language barriers are a bi*ch and I don't think the important points were understood by either of us on this deal.

If there is no performance advantage to 45's over 40's, I guess I will have to mount the rims and tires on the car and take a look for myself. Maybe I can get my fat neighbor to come hop around in the trunk to simulate the rear end on a bumpy road. If there is any insight somebody can give me as to how the profile of a tire plays on performance, I would appreciate it! Thanks to you guys who have already replied.