SBC_and_a_stick

http://www.tirerack.com/tires/tires....0ACR&tab=Sizes

The ACR tire package is only $1,400 for a set of 4, wider 355 rear section, and longer lasting at 200 wear rating. The front seems to fit on the stock Z wheel. What about the rear?

sammyv

They only come in 19's. Do you have a Z07? 19's(new wheels) may clear steel brakes.

SBC_and_a_stick

I have a Z07, so they have to clear CCBs.

Any clue as to whether the ABS will go crazy on me? the rear diameter would be .8" higher and the front would be .9" lower.

I don't use PTM so I don't care about traction control, stability, or any of the PTM race/sport settings.

four0nefive

19" wheels should easily clear Z07 brakes. The Z28 has a square 19" setup with the same CCBs.

dvandentop

18 inch track wheels clear the rear so 19s for sure should

ElCid79

I am pretty sure you do it like this...

PRE-Z06

I asked a similar question in the zr1 section, but never got an answer...I don't see why you couldn't run a 19x12 replica rim which was my thoughts on z07 c6z
https://www.corvetteforum.com/forums...345-30r19.html

SRTRick

From looking at the tires on a Viper yesterday, the one thing I believe is that you will for sure need 11" front wheels due to the extremely low sidewalls, and I don't think anyone makes inexpensive cast wheels in that width for the front. The rears have a high sidewall and would probably be ok on 12" wide wheels, but if you are building custom wheels anyway why not go with 13s so they are exactly to the Kumho's design parameters.

At one point one of the photos of the tire showed a 20 treadwear rating, not 200, but I didn't bother to look to confirm that on the actual tires because those ratings are pretty subjective anyway and you don't really know til you wear a set out. The standard 720 tire is a 200, but that is a very different tire with different compounding tread design and construction. I will look at the tread wear rating on the actual tire if I have a chance to get back to that dealer to confirm what it actually says on the tire. Tire Rack says they are 200, but they have almost no dimensional data for the tires so they may have assumed it was the same as the standard 720.

FWIW, I missed this post and tried starting my own because Kumho wasn't in the title, so, sorry for the duplication.

SBC_and_a_stick

Great input! Indeed, it seems a 19x11 and 19x13 setup is the ideal choice.

I've done some homework so I'll share.

Presumably ABS, AH, and TC require that the front wheel diameter is close to the rear wheel diameter. How close? Within 5%. A secondary concern is that the drive wheel ideally needs a larger diameter (if different than the front) to not trip TC. So where do we stand with Viper ACR diameters? Bad, real bad. The difference is roughly 10%. No way in hell you can get away with this setup. The sensors on board would go mad.

Anyone disagree?

SRTRick

What kind of differences are people using the Continental scrubs running I wonder. I looked at the available sizes for new Conti slicks and didn't really see a stagger that looked appropriate. The Michelin slicks looked better but haven't heard about anyone running them. I was just hoping to find a economical choice for track duty. May have to go to 18s for that.

Where did you find the full specs for the Kumho's, I couldn't find them anywhere?

SBC_and_a_stick

I believe Frank was running the Conti's. Worth a PM for sure.

18"s are more economical, but you have to figure in that the fronts a re a bitch to balance around massive CCBs, and that most if not all 18's that fit around CCBs are forged/$$. Cheap only if you don't count expenses on the wheel itself.

SRTRick

I figure the wheels are at least somewhat long term while the tires are definitely consumables. Where did you find the dimensions on the Kumhos? I couldn't find them when I looked. Does Jon B have the dimensions listed somewhere?

I don't have the Z07, so clearance is less of an issue for me.

SBC_and_a_stick

I just used a tire diameter calculator. If the Kumhos are underrated or overrated I will obviously be wrong. But, it's not likely it will be so different than what it says on the sidewall that it accounts for a 5% lower difference in diameter. If anything, both fronts and rears are Kumhos and they will be "off" from spec in the same direction.

SRTRick

I'll try to get some data from kumho on dimensions as sometimes they play fast and loose with the stated sizes and not necessarily consistently.

SBC_and_a_stick

Sounds great. Looking forward to what you find. Ultimately, I've decided I'm game for mixing and matching brands/types of tires. Those Trofeo R's from the Z28 would match the ACR rears quite nicely imo.

Fitz89

I am running 19" and have been for a few months, my second set of wheels just came in. Running R7's
Plenty of clearance- even lowered- and optimized.

GTB/ZR-1

If one runs w/ all the nannies off--wouldn't that be the workaround?

SBC_and_a_stick

Looks awesome. The diameter looks almost identical for your tires. How close are they?

ABS is the one I'm worried about. If TC and AH don't work I don't really care. I turn them off every time I drive.

SRTRick

OK, so I got the dimensions from Kumho and it looks like the size differential might indeed be a problem. The wheel selection is actually more flexible than I thought it would be from looking at the front tires, as Kumho says that 10"- 11" wide wheels will work on the fronts and 12"- 13" wheels will work on the rears, but the diameter of the front tires is 24.9" while the rears are 27.5", a bit more than a 10% differential. The stock Z07 cup tires are about a 3% differential, so I'm thinking there would be problems, even with the ABS.

It's too bad the cars software can not learn new diameters while driving in a straight line and recalibrate the various affected systems, but I guess that would be asking too much from them.

mfain

Kumho track tire wear? LOL