tire size issues
Thread Starter
4th Gear
Joined: Feb 2021
Posts: 4
Likes: 0
tire size issues
What's up everyone! I have been a lurker here for awhile. I own a 2005 base z51 coupe. Cammed bolt on car. I bought the car last July, it had ZO6 oem wheels and tire sizes on the car NO issues. I pulled the wheels off and sold them along with the rear P325/30r19 run flat rear tires. I kept the front two tires & installed 18/19 zr1 replica wheels that fit a base not wide body wheels. Tire size in the front is P275/35r18 rear is P305/35r19 Nitto NT05R drag radials. Im having an issue with the ENGINE DRAG CONTROL ACTIVE message. Randomly when i down shift or let off the gas in any gear minus first the ENGINE DRAG CONTROL ACTIVE message will show up & car will lunge forward as if i was blipping the throttle. Sunday I did a 2nd gear WOT pull getting on interstate pushed clutch in and engine revved up repeatedly to 6000 rpm showing that message on DIC. First time that ever happened... Anyways, my question is what would be the ideal front tire size to stop this issue from happening? I have searched over & over, cant find a definite answer.
Last edited by CROWNC6; Feb 3, 2021 at 11:20 AM.
Instructor
Joined: Jun 2018
Posts: 247
Likes: 116
From: DFW, TX
The difference in diameter between your current tires is to great.
Stock C6 base is front 245/40 18 (25.7 dia.) and rear 285/35 19 (26.9 dia.). Difference in dia. is approx. 1.2 (rear larger).
Your tires are front 275/35 18 (25.6 dia.) and rear 305/35 19 (27.4 dia.). Difference in dia. is approx. 1.8 (rear larger).
You must keep the difference very close to 1.2 or the car thinks it's out of control and will try to correct it. And no you can NOT correct this issue with a hand held tuner.
Good luck.
Stock C6 base is front 245/40 18 (25.7 dia.) and rear 285/35 19 (26.9 dia.). Difference in dia. is approx. 1.2 (rear larger).
Your tires are front 275/35 18 (25.6 dia.) and rear 305/35 19 (27.4 dia.). Difference in dia. is approx. 1.8 (rear larger).
You must keep the difference very close to 1.2 or the car thinks it's out of control and will try to correct it. And no you can NOT correct this issue with a hand held tuner.
Good luck.
Drifting
Joined: Oct 2007
Posts: 1,417
Likes: 486
From: NY
I agree with ki-speed. For reference, I had 275/35-18 F on an 18x9.5" wheel and 295/35-19 R (MPSS) on a 19x11" wheel on my 2009 coupe (w. Z51) and had no problems. The difference there is calculated at 39.4mm. Your sizes represent a difference of 46.4mm.
If you're dead set on keeping the rear setup, a 285/35-18 front with the 305/35-19 nets a 39.4mm difference as well.
I'm not sure on c6 owner experience with that size up front, so you'll want to do some more research. Of course, wheels offset will also come into play. Also you didn't mention the wheel widths, which is important in fitment and handling/tire performance. If you're running a stock 8.5" width wheel up front, then either a 275 or 285 is not a good idea.
I won't check back on this thread, so good luck.
If you're dead set on keeping the rear setup, a 285/35-18 front with the 305/35-19 nets a 39.4mm difference as well.
I'm not sure on c6 owner experience with that size up front, so you'll want to do some more research. Of course, wheels offset will also come into play. Also you didn't mention the wheel widths, which is important in fitment and handling/tire performance. If you're running a stock 8.5" width wheel up front, then either a 275 or 285 is not a good idea.
I won't check back on this thread, so good luck.
Thread Starter
4th Gear
Joined: Feb 2021
Posts: 4
Likes: 0
18x8.5 front's 18x10 rear's. I do want to keep the rear tires on the car if at all possible. I am aware it cant be tuned out or adjusted. Im open to using a P275/40R18 if tire will clear in the front. Or go to a slimmer but taller tire such as a P245/45R18. Both of these tire sizes should work from my understanding of how the car works. Wondering if they will fit and not cause rubbing up front & fix my issue.
Last edited by CROWNC6; Feb 3, 2021 at 01:45 PM.
