Hello everyone

About to pull the trigger on some Enkei RPF1s 17x9 +45 however I can't decide on tire size!! Its either going to be 245/40 or 255/40. I know the 245 is a safer bet when it comes to rubbing and thats kind of what I'm leaning towards but I also know a lot of people use 255.

-Looking to get RS 4 tires

-2.7 degrees in the rear and 2.2 front

-Not a daily driver

-Plan on doing the odd track day here n there

-Going to be lowered on KW v3

-Willing to roll and relocate bumper tab but I'd rather not pull; I want to keep the stock look

 

Roll and bumper tab relocate is a must and so will be a fender pull.
Maybe at -2.7 on 245s depending on tyre brand you could get away without a pull but you should do it anyway to be safe.

Here are some pictures for reference on a meaty 255 AD08R;

PSS9 at a high ride height with -1 deg camber on fronts. It sticks out of the fender by at least 1/2 an inch



Same meaty AD08Rs but well worn with -2 front camber lowered without a a 1 ~ 2 finger gap and my fender have been reshaped to give me about 1/2" extra room

 

Do a 255 in the rear and 245 up front if you want the most traction without having to pull fenders with these wheels. Your still going to need to watch it up front, so dont go too low on the coilover height. 13.2"-13.5" fender to center of hub would be my suggestion.

 

I'd go 245/255 like Junky says.
Everybody seems so so fixated on 255/40-17 square, but I have to think that 245s aren't going to lose you much lateral grip and will be lighter-weight, with shorter sidewalls, and more favorable fitment on 9" wheel for track work. At the very least you should get better steering feel with 245s up front. Not to mention practical fit reasons...

 

Cost and the ability to rotate for me was the main factor. I was just being stupid to by 255s rather than 245s all round.

 

So you can buy 4 tires all at once instead of two? Cost the same as far as I can tell. The ability to rotate is over rated in my book. I get it in principal, but in application doesn't make that much sense.

 

255/40s are a standard front size in the STR autocross class...the max by the rules. The rules stipulate a 17x9 rim. With -3° camber they work with rims that are +60 to +65. In the B/Street class, limited to -1.9° by the rules mounts. they are on 7x17 rims by the rules, with either OEM +55 or up to +48, again limited by the rules.

I'd recommend a different shock.

 

245's on a 9" wheel, 255's on a 10"

Pass on the KW's

 

Actually, on +45 you might consider 235/40-17 fronts if they're available in your tire choice. Hankook RS4 comes in that size, btw.

If you haven't bought wheels yet you might consider PF01SS, which come in 17x9 +60. MUCH better/easier fitment.

 

949Racing also comes in a more fender friendly offset 17x9 +55

What you pick up in grip from an extra 10mm, you give up in reduced feel/feedback. Unless you're looking for every last fraction of a second, you likely won't notice the difference stepping down to a 245.

With a +45, if you go low, you'll need to be cautious. 245 is a better fit up front.