WoodiC7

Wheels and offsets? Sidewall ratios?

varun

I have a stock C7 Z51 and I find the tires too skinny. On stock OEM wheels, how wide can I safely go without any rubbing or hurting the brake ducts?
If I dont care about getting stranded, can I go with non runflat tires? The options for Pilot Super Sports are vast in the non RF option. 285 is too skinny for the rear, and something like 305/30/20 or wider in the rear would be swell. Had anyone done this, and something similar with the fronts too?

Theo Harris

Call John at CCW
Ordering/Technical Phone
Phone 1.386.258.0083
Fax 1.386.248.0150

Ordering/Technical Email
ccwheel@gmail.com

Facility/Mailing Address
Complete Custom Wheel
618 Ridgewood Ave
Holly Hill, FL 32117

Facility/Phone Hours
Mon-Fri 9am-6pm
Sat Closed
Sun Closed

Theo Harris

I think it's because they also need it to get 29 miles per gallon out of the car and that's not happening with 325's etc

Theo Harris

Rears are not a problem 19 @12 with 325 r888's

The fronts originally were built as 18" 10.5 with 295 r888's and they did take the brake ducks out
John at CCW made me new front wheels @ 10 and he is going to put the 295's back on my way to Sebring Florida this weekend I will PU ( we will see)

WKMCD

Theo,

I've run 2 set of wheels from John and Chip. What model wheel are you running? Are they flush/inside the fenders or do they stick out?

Kevin

varun

Any1?

brucesallen

For track road racing, I really want Hoosier R6 and 295/30-18 and 315/30-19 looks like a good pair. Anyone using R tires in road racing?
John at CCW says his 19" won't be available for 2 months! Tire Rack is trying to see if an OZ will fit. They found out OZ does NOT make a 19" that will fit! Finspeed is checking.

Z513LT

I'm going to 325's in the rear on a staggered 20/21 setup. I'm assured they fit cleanly with no rubbing. I'm not going to tempt fate by going any wider. The downside is that the only tire company I've found who makes the prerequisite sizes for this setup is Pirelli. P-Zero isn't a bad tire but there are others I'd rather be running.

Here are the specific tire sizes:

265/30R20 front
325/25R21 rear

I'll report back once I've had a week or so under my belt with the new setup.

descartesfool

What width and offset wheels can you run for 18" wheels front and rear? That wheel size gives you the option to run slicks and R compounds on track. A good choice might be Nitto NT01's or Toyo R888's in 275/35/18 (25.6" O.D.) front on about 10" rims and 305/35/18 (26.4" O.D.) rear on about 11" rims. The wheels would also fit Hoosiers in the same front size and 315/30/18 (26.1" O.D.) rears. Then on the same wheels you could run slicks in a 270/650-18 front size (25.6 O.D.) and a 300/680-18 rear size (26.8" O.D.). That would be a ton of options for tires to run on track, and cheaper than 19" sizes. Some people can get take-off slicks in 18" as that is one of the most popular wheel sizes for slicks.


Question is which size wheels and tires work with brake calipers and ducts front and rear, if one can run 18's all around.

brucesallen

Good info. In fact CCW is steering me toward all 18" because they will be out of 19" for a while. And I really want the much stickier Hoosier R6. Perhaps R6
295/30-18 and 315/30-18 would work. The only thing that I worry about is the stock Michelin Pilot SS are
F 25.7 dia., R 26.5 dia (.8” difference) and the R6 F 295/30-18 is 25.3 dia. and R 315/30-18 is 25.6 (.3” difference). Not important to traction control, track mode?

descartesfool

Unless someone figures out otherwise, I would keep the same ratio of front to rear revs/mile on any tire setup for the C7 as the OEM setup when opting for any other setup to insure the traction control and ABS all work properly.

On my Z51, 245/35/19 fronts have 807 revs/mile while the 285/30/20 rears have 770 revs/mile, so the ratio of front to rear is 807/770 = 1.048, or a 5% greater revs/mile for the fronts over the rears.

So for my picks, a 275/35/18 has 809 revs/mile and 305/35/18 has 790 revs/mile giving a ratio of 1.025, so 2.3% off OEM ratio which is perhaps OK. I also have a GT-R, and the computer warns you if you go more than a few % points away from OEM front/rear ratios, but it is AWD, so it might be more sensitive to that.

Fugitive C7

With AWD you're talking about transmission/transfer case problems with the ratios being off. Completely different reason to care than RWD

descartesfool

That is certainly true, but ABS and traction/stability control work based on different speeds between the tires, front and rear and side to side, and that is related to the diameters, whether RWD, FWD or AWD.

B Stead

Oz Superleggera III
Front, 18 x 9.5, 59mm, use 5mm spacer, about $900 each, listed under the C5
Rear, 19 x 11, 75mm, about $900 each, listed under the C6

But at wheel offsets of about 52mm front and 74mm rear, 9.5" wide front wheels and 11" wide rear wheels are the widest that I can find without going to a custom built wheel.

And the Cray 2014 line has 9.5"/11" wide wheels at the correct offsets.

Basically, for tires wider than 275/315 then the wheel widths should be 10"/11.5" or wider
.

brucesallen

So I went with CCW 18x10 and 19x11s and Hoosier R6 285/30 and 315/30. These have the same difference in F/R diameter as stock. My club penalizes tire sizes over 305 and I don't want to get bumped a class.

New issue: I am told that I must use TPS even on track tires or the C7 computer will limp-home and use of TPS cannot be turned off. True?

Third issue: Brake rotor add-on air flow discs for track- I plan to paint them with hi-temp paint to avoid rust and leave them in place for street use. Problem?

descartesfool

Sounds like a nice setup. Let us know how it works out, and if tires clear the brake ducts front and rear, and any issues that might arise in terms of rubbing.

Don't know about the TPS, but for the brake rotor rings, if you paint them, the paint better be super high temp as otherwise paint will burn off. Not sure any paint can last with rotor temps, which is much higher than caliper temps. Perhaps a ceramic coating would be best, as used on headers.

brucesallen

I will report after May 8, 9 track day and Tile Trial with COM Sports Car Club (Corvettes of Mass). The temperature at the pad/rotor interface should not exceed 1,200 deg F. Down near the hub where the ring is installed it should be a good deal less. I am using 1,200 degree engine paint. (HAO) Thermo Tec 11oz Aluminum Hi Heat Coating from Pegasus Racing.

Theo Harris

Just came back from Sebring Florida with the National Corvette Museum ( amazing 2 days of HPDE)

The C7 Z51 is one amazing car!

Went by Daytona Beach on the way to Sebring and John at CCW delivered as promised ( he opened the shop on Sunday and took care of it personally ) the 18X10 new wheels and transferred the 295's R888's from the 18x10.5 wheels (previously made) the car handled amazing on the track and the abused of 2 drivers back to back at Sebring

When we finished at the track change oil, put the stock brake pads, corrected the alignment and checked the car underneath without a single scratch!

( btw there are bulletins about the engine oil, we can start a new file on the C7 oil as most service stations and dealers do not now what to do and correctly check and fill the car properly)

No rubbing or any kind of trouble with the wheels, tires or the brake ducks!

All clear!

Theo Harris

#2 You need tpms...I got mine cheep from tire rack and they did not work...went to the dealer and paid a fortune and got them done.

#3 I thing this is a really bad idea as the rings are temporary secured by 3 small pieces of wire ( quite pure design and and afterthought if you ask me of GM)

If you are tracking your car regularly bite the bullet and get a AP Racing track kit $3500
Or
If you drive it mostly on the street get the Brembo at $4k