bgibbs678

I will be autocrossing and doing a few hpde days with my 2003 z06. Getting a headache with the tire options and sizes. Anyone running the falken azenis rt615k+ front 275/40r17 and rear 315/30r18? I'm wondering if the 40 sidewall will look funny and cause an issue with performance. Diameter will be 25.6 and rear 25.5.
I don't want to get a separate set of wheels at this time I'm so looking for optimal tire performance for A-street. My other thoughts are rs-4 255/285 or rival s 255/315. Thanks.

bgibbs678

What tires? The only 305 I found was r888 which can't be used in a-street

REKCUF

Nitto NT01

69autoXr

I don't run AS, but I am familiar with some of the setups. From a National perspective I'm not aware of anyone running the Falkens with any measure of success. I would be looking at either the Bridgestone RE-71R or BFG Rival S, and I know you said didn't want to buy wheels but I would highly recommend moving to 18's in front and getting the 275 in either of those tires.

BTTBSS

I run 255/40/17 and 315/30/18 for autocross, HPDE and street. The RTK 615+ are a nice tire. If you are an experienced Autocrosser and plan to win in A stock this is not your set-up as others have mentioned. If you are new to the sport and want a good multi-purpose tire, they stick well are fairly quiet on the street and won't kill you in a light rain. FWIW I am thinking of trying 275/40/18 front with 295/30/18 rear when these wear out to get a bit more rubber in front.

thethrillofspeed

I run 315/30/18 Rival S on all four corners in CAM-S....I was very pleased with the big rubber up front.

BTTBSS

Are you using stock Z06 rear wheels with the 315's Wondering about clearance.

69autoXr

Not a Rival, rather a Hoosier, but to give you some idea of how a 315/30-18 fits the front on a stock rear-spec replica wheel.

bgibbs678

Are those the replica wheels from OE Wheels LLC? I saw a set I wanted to buy 18x9.5 and 18x10.5 but I heard they are 11 pounds heavier? any issues with the wheels?

69autoXr

These particular replicas are by Factory Reproductions, and these are only about 1 lb heavier than stock rears. I dont run them that often but haven’t had any issues when I do.

I also have a set of OE Wheels C6Z replicas in 18x9.5 and 10.5. I’ll have to weigh them again but I know the difference wasn’t 11 lbs.

EDIT: I weighed the OE Wheels C6Z replicas and came up with the following weights: front 23.2 lbs, rear 23.1 lbs. I also weighed factory front 17x9.5" and those came in at 19.2 lbs, I don't have a stock rear unmounted but from what I remember they about 21 lbs.

insertclevername

If staying with factory 17/18 wheels the choices are very limited.

Size, compounds differing front to rear (PS2) and speed ratings all seem to play against a good choice.

I would suggest running 255 f and 285 rear. There are a couple good choices. Then decided what tracks you'll be running on. If I'm hitting Daytona Speedway banks, I'm not running a street W rated tire. Because this is a track I have been on, and plan to do in the Z06, I won't buy anything but a Y rated tire. Now if I move away, where I have tracks that don't have sustained 170+mph, I'll pick up W rated tires.

Some more food for thought in the 17/18 wheel search game.

69autoXr

added weights for the OE Wheels C6Z replicas in post #11

jcarothers

I have that tire setup on my car currently... They're okay. I'm planning on running 315 BFGs on square 18x11s next season. And the intent for the Falkens on stock wheels was for the end of this autox season/set I can do track days on.It works, but its not the ideal setup for autox as the Falken has nowhere near the pace of the Bridgestone and BFG. The only reason I have them is they wear a little slower than the other two brands and had more favorable sizing for stock wheels. If you're looking for a more competitive setup on stock wheels, go with a 255/285 combo in a more favorable tire. The width you give up is not equal to the grip the other tire compounds have over the Falkens.

Drewster67

Sure you can, if you live in AZ or CA.

insertclevername

Just a reminder for those that may have overlooked the ratings.

Toyo R888 are different speed ratings for the 17 and 18 sizes.

MX621

I believe the hankook rs4 255/40/17, 285/35/18 is the best 200tw Street/track tire for our cars right now. They run on the wide side to. I’m currently on 275/40/17, 295/35/18 NT05’s which run narrow. Come spring I’ll be going with the hankook.

C5Luv'R

Does the 315/30R18 clear the stock wheelhouse when mounted on a stock C5 Z06 rear wheel?

bgibbs678

I just looked on tire rack and do not see the rs4 in the 255/40r17 anymore. Has anyone every ran mismatched tires? Different front and rear? I’m wondering if the Star spec 255 with the rs4 285 would work.

Thaddeus Snaith

I was doing some similar research and found the sidewall to be only a 1/10" taller with the 275/40/17 which really only raises the car up 2/10". Seems to be a viable option.

Tad

Thaddeus Snaith

Thanks, that's good to know. I'm seriously considering running 275/40 with my car.

Tad