Bill Dearborn

Title pretty much says it all. Will a 305/30/18 fit if I am using the stock 18x9.5 wheel size? I know the wheel width is right at or just below the minimum recommended by the tire mfr but I was wondering if there would be any other issues. I am looking at Toyo R888s. I have Nitto NT05s 285/30/18s on LG World Challenge 18x10 wheels that rub the edge of the front fender under cornering load.

Bill

dvandentop

yep i have ran them no problems at all even with brake ducting, just dont turn lock to lock and u will be ok.

i however have not ran them on a stock rim

Kubs

I do not have a C6Z but I have 4 OEM front wheels that I use on my C4. I use 275/35 Hoosiers and they are the max width I would run on that wheel. Hoosiers usually run a little wide and the 275 is probably close to the 285 you are currently running. If you go any wider you are going to start rounding the corners and you may actually reduce your contact patch. Im sure it will "fit" the wheel but it wont be a good use of the tire.

froggy47

My friend has a 2011 GS with that size in a Kumho 710 (wider rim) He has a little rub on hard corners, not a big deal, fender well.

Bill Dearborn

What size rim did you run them on and what was the offset compared to the stock rim? After taking some measurements it looks like my 285/35/18 Nitto NT05s on LG World Challenge Wheels stick out about .8 of an inch further than my stock EMTs mounted on stock wheels stick out. The Nittos just hit the outside edges of the fenders under hard cornering. If I put the 305/35/18 Toyo R888 on my stock 9.5 rim it will stick out about .7 of an inch more than the EMT but will also be a half inch larger in radius than the Nitto.

Bill

kentz06

Hoosier R6 305/30-18 on a CCW C14 18x11 clears except at full steering lock. Car is slightly lowered.

Perhaps John at CCW could give you information about offsets from stock rim to the C14. (IMHO, however, you might consider the risks of using a cast wheel on the track over an extended period of time.)

The jump up from 295 to 305 helped reduce understeer.

Bill Dearborn

Been using cast rims on the track for 18 years without an issue. Both GM and aftermarket. The LG wheels I had been using were cast and I would still be being using them except a brake pad guide pin came out of the caliper and screwed up the spokes. The choice is buy a replacement or go to an 18x12 repro (cast) in the rear with a stock front and get different tires.

Bill

dbratten

Not a Z but I run the 710 305x30x18 tire on a 10.5" rim on my C6. Rubs the C6Z brake duct a little but my wheels are set in farther than yours will be. My 10.5 58mm has a 8" backspacing. Your OEM 9.5" 40mm wheel has a 6.8" backspacing.

Bill Dearborn

My concern is the outside of the fender. With the 285s on a 10 inch wheel I had no brake rub issues but the trim tab that sticks out of the front fender well would be rubbed quite badly by the outside of the tire under hard cornering. It didn't rub when the car wasn't being driven hard.

I took some measurements today. The width of the LG wheel is 5/8 of an inch wider to the outside of the car than the stock wheel. With the Nitto on the wheel the tire is a total of .825 further out than the stock tire on the stock wheel while being larger in radius by .15 inches. The Toyo R888 305/35/18 mounted on the stock rim will be about .7 wider to the outside than a stock rim with an EMT but it will also be .35 in larger in radius which may move the larger section enough to make the tire touch the fender. Then there is the issue of mounting it on a 9.5 in rim which may make it bulge more.

I don't want to tear up the fender. If the issue was a brake duct I wouldn't worry.

Bill

froggy47

When you get to it, tape up the fender lip with alternate layers of racer tape/alum tape maybe 4 layers. Check after 2 - 4 laps. Should show any rub & not hurt fender.

JDIllon

I have been running 315s with no problems except at lock to lock. JD

dvandentop

bill i am using same as dean (kentz06) used 18x11 ccw up front

Painrace

I just tested the Goodyear DOT Rs 315 fronts and 335 rears. Both are wider than Hoosers and are faster. They look very, very close but there is no rubbing. As will be out soon.

Jim

froggy47

I have info from a well regarded source who also tested a set, that the sidewalls are softer than a6 & 710 so that you have to run more psi to get the flex out. Did you find that to be the case?