The setup on my FD:

front- 18x8.5 +38
rear 18x9.5 +40

I'm running a 235/40x18 in the front

Wanted to know if i should run a 275/35 or 265/35 in the rear? or is 275 to much?
where i live theres a lot of twisties and mountain driving.

 

Run a 235/40-18 in back as well.

That is the max recommended wheel width for most performance 235/30-18 tires so it will have great sidewall feel and not stretched beyond manufacturers recommended sizing.

That will keep the car balanced so its not an understeering pig in the twisties.

 

But whats an ideal size on the 9.5" wheel if the fronts were 9.5 as well?

 

IDK, ideal will vary by person.

I prefer a 255 on a 9.5" wide wheel.

Wider than that and it starts to feel slow to respond to me. This will vary by individual tire's sidewall as well.

 

kumho XS 245/35/18 work well on 9.5" wheels (9.2" tread width).

a 255/35/18 RE-11 would work well 9.4" tread width.

 

I leaning more towards a 255 or 265 width in the rear.

 

on a 9.5" wheel, run a 255/35/18. it will provide better traction and more predictable handling than wider tire sizes. I am guessing we are talking about extreme tire selectons as they run pretty wide.

 

I'm going to be running a high performance summer tire. I just don't want the tire to be too stretched on as 9.5 wheel

 

a 255/35/18 tire is not stretched on a 9.5" wheel. 235/40/18 would be slightly stretched, definitely not a 255.

 

I'm running 18X9.5 +45 Enkei RPF1's with 275/35/18 Toyo R888's on all four corners.

I'm lowered on Tein coil-overs on stock fenders, pulled and rolled.



Would I recommend it? Ehhhh....not really.

These wheels are just loaners from my boss at work (awesome boss, right?)... Otherwise I wouldn't normally run something so wide up front.

I can turn fully, but I do hear the tire lightly scrape against the fender liner plastic a little bit sometimes. The fender liners are admittedly a little beat up and the clip/mounting points had to be cut when I had the fenders rolled which is probably why/when it scrapes. Otherwise, it might actually be just fine.

I have a friend who ran 285/35's on his LS1-FD on stock fenders and never scrubbed but he was at stock ride height.

If you are lowered at all, be warned.

On stock fenders, lowered...I wouldn't recommend more than 255/35/18 personally. Just for the sake of it.

255/35/18 on a 9.5" rim is a perfect fitment, btw. The 275/35's do balloon a little bit.

 

I ran 265/35/18 on 9.5" on all four corners for roughly 5 years and never had a problem with rubbing. I just purchased four 255 tires for my wheels. I think this size will perform better but I haven't had a chance to drive the car yet.