GunKata

I've been searching and seeing multiples configurations with the tire sizes and saw the post with what sizes you can run with what brands and from what I can gleam, I can run this setup:

275/35/18 Front

295/35/19 Rear

Most likely going with the KDW2s here. Now, what is the difference/advantages/disadvantages with going 275 up front instead of just one-upping like the rears, and going 255 front? I will be mounting the tires on Factory repros that are in the stock sizes.

Any info would be great, I just have a hard time wrapping my head around the idea that the rears only get slightly larger, yet the fronts get much larger and thats "OK".

Thanks,
John

GunKata

tttt

SteveC6R

You need to look at what the tire dimensions are. You don't want to get to much rake. When I first bought mine I used A6s in a 245/295 combo as they were the only thing that wouldn't throw the car out of wack. I finally got tired of trying to come up with a bigger tire for the C6 and had a set of CCWs made, solved the problem.

Uncle Sam

Tire width involves obvious stuff like will it hit the body of the car at any point during steering and suspension movement. The second thing to consider is handling balance and wider generally gives more grip at that end of the car. The problem/ exception here is in sidewall stiffness which relates to tire width and rim width ratio. Finally, overall tire diameter is a big deal with our computer controlled Active Handling. The two tires sizes you mentioned in BFGs have an overall diameter of 25.6 inches front and 27.0 rear in the KDW2S. The stock Vette diameters are, on my 2008 Z51, are 25.7 front and 26.9 rear. So this looks good. The slightly lower ratio of front to rear width difference would give more front grip or a more oversteering dynamic. Check my math, but this doesn't look bad. Whether it will work on the front is something to check, I don't know.
P.S. I am going nuts deciding what tires and wheels to run for HPDEs.
SteveC6R, what CCWs and tire combo are you running?

GunKata

Thanks guys. There is a post that I believe either JPschindler made or another of the dedicated guys on here made where those sizes did work, but I guess I'm just trying to see if I am missing anything else here. I would like at least 10mm wider for both tires, but I just find it odd/interesting that you can 10mm up on the rear, but go 30mm up on the fronts and that seems to be ok. I am just looking for confirmation on that.

GunKata

Found it, Silverton had posted this:

"Here is a table of tire combinations for 19" rear wheels:

Front Size / Front OD / Rear Size / Rear OD / Height Difference / Tire

245/40-18 25.7 285/35-19 26.9 1.2 OEM

275/35-18 25.6 285/35-19 26.9 1.3 PS2, GS-D3, KDW2, PZero Rosso, Advan
275/35-18 25.6 295/35-19 27.1 1.5 KDW2, Kuhmo Ecsta MX
275/35-18 25.6 295/30-19 26.0 0.4 PS2, RE050A, PZero Rosso, Advan, R888
275/35-18 25.6 305/30-19 26.2 0.6 PS2, RE050A, PZero Rosso, Advan, R888 (2008)

265/35-18 25.3 285/35-19 26.9 1.6 KDW2, Advan
265/35-18 25.3 295/30-19 26.0 0.7 PS2, PZero, Advan

255/35-18 25.0 285/35-19 26.9 1.9 KDW2, PZero Rosso, Advan, RE050A
255/35-18 25.0 295/30-19 26.0 1.0 PS2, PZero Rosso, Advan


Here is a table of tire combinations for 18" rear wheels:

Front Size / Front OD / Rear Size / Rear OD / Height Difference / Tire

245/40-18 25.7 285/35-19 26.9 1.2 OEM

275/35-18 25.6 295/35-18 26.1 0.5 PS2, GS-D3, KDW2, PZero Rosso, Advan, Ecsta MX
275/35-18 25.6 305/35-18 26.4 0.8 R888

What's missing here is this: What is the minimum height difference between the rear tire and the front? There have been several reports that the 275/35-18 front with 305/30-19 rear (height difference = 0.6") may work. If that combination works, then perhaps any height difference greater than or equal to 0.6" may be OK. There are also reports that the combination 275/35-18 front with 295/30-19 rear (height difference = 0.4") does not work very well."

gkmccready

275 on an 8.5" wide rim might be a little pinched. The tirerack website says the KDW2 would like a 9" wide rim as a minimum. But I suspect it'll fit; it just won't be optimal.

295/30r19 doesn't look available in the kdw2, but the 295/35r19 is. It looks to be ~27.1in tall vs 26.9in for the stock tire.

If you're really looking at a 295/30r19 that's only ~26in tall, that's only about a 0.4in difference front to rear, so I'm not sure what the computer will think...

FWIW, I'm running 295/30r18 on CCW 18x11 in the front, and 305/35r18 in the rear. I've run 18x11 in the rear to date, but I've got some new CCW 18x12 in my living room right now to try. I sent John pictures of my car on track and we decided there was room for another inch in the rear.

'06 Z51

GunKata

So maybe 255/295 is the way to go? with 35 for the rear profile. From the specs on that tire on their site, it looks like that combo is probably the best way to go.

SteveC6R

I run CCW 18x11 all around with Hoosier 315s on all four corners.

Gordy M

I have run the 275/295 combo for the last two years with no problems. The 295 were 30 aspect and the 275 were 40. This will give you a 25.6 diameter all around. The important part is to maintain the proper RAKE for the car. Measure at the Jack points on the frame on both sides--never use distance to wheel well lip--and maintain at least a .25" lower front.

gkmccready

Since he's talking street tires he wants the difference front:rear to keep the computer happy...

GunKata

I don't know... maybe I will just go stock sizes, can't really figure out whats what here and don't want to make any costly mistakes.

gkmccready

Call John@CCW and ask him. They sell tires as well as wheels.

GunKata

Thanks, I'm just surprised no one on here can comment on this.

gkmccready

Most guys here run DOT-Rs or slicks; and most folks are in a C5. The C6s seem a little more ornery with the electronics. On top of that, most guys in here turn off all the TC/AH when they put on their track wheels+tires so not many have experience with trying to run tires for the dual purpose while wanting the TC/AH to remain functional.

You might try C6 Tech as I bet there's more folks there trying different sized street tires and trying to keep the electronics happy.