Team Lazy

I just "acquired" a set of CCW's for track wheels for my 04 Z06. They are sized 18x11 and 18x12, and I'm not completely sure what size of rubber I can run on them.

Reason being, I'm aware of some of the problems some folks have with the traction control (using same size front and rear), but more importantly I don't know if the 12" wheel will take something SMALL enough that I won't have rubbing/interference issues. Does that make sense? IOW, does a 305 fit on a 12" wheel? Or a 275 fit on an 11" wheel? I've heard that 315's rub, so I just want to know if I'll be OK with "regular" sizes on these monsters.

ALSO, can somebody explain slick tire sizing? As in the aspect ratio (I ASSume?) and how it's calculated? For example, Pirelli RR slicks are sized 305/675/18. I'm just curious how they calculate the "675" part, or in other manufacturer lingo they use inches, but I'll assume it's the same formula.

Thanks fellas!
JJ

Cloaked323

I head from some I would consider reliable that in short the front tire can't be larger than than the rear, you want to use a 30 front a 35 in the rear, lastly the the closer the diameter between the front and rear the less chance of setting off the nannies.

thehammer69

I have those same wheels on my 02 Z06. I run 315/18 Hoosier A6's on the front and 335/18 Hoosier A6's on the rear. My wheels have an 8.25" backspacing on the front and 8.75" on rear. The fronts only have any rubbing issues when I turn full lock...so I don't do that. The rears are rubbing the inside fender liner when at hard compression. I'm gonna try to fix that by adding 1/8th inch spacers.

Sidney004

The 305 is tread width in mm, the 675 is diameter in mm.

Jason

If it was me, I'd sell those CCW's for big bucks, and buy a set of stock sized C5Z06 rims for next to nothing.

Team Lazy

The thought occurred to me, but I've been looking for used Z06 wheels for awhile and they're just too damn expensive up here. So I'll keep these, they're pretty sexy. They have ARP fasteners all the way around too. Is that normal?

Also, what I'm really trying to figure out is, can I run more "normal" size rubber on these rims or are the rims too wide. IE 275's on the 11" and 305's on the 12"?

froggy47

If you go to Tire Rack and look up the tire the specs will tell you the "recommended" min/max rim for any tire size.

davidfarmer

305/675/18=305/35/18

305*X*2+18*25.4=675

you just have to solve for the "X" that is the missing part. In this case, X=.35

and in case you didn't know, 25.4mm/inch

GT Racing Tires

I run the same size wheels and use Pirelli D2 slicks in 285/645/18 front and 305/660/18 rear.

Just happens that we have a few hundred of these tires in stock plus Continental slicks in the same sizes.

Todd
414-350-6303

Team Lazy

Thanks Froggy, but I tried and couldn't find it. Weird, as they have awesome info there and the site's pretty slick. But I just couldn't get the link.

Thanks! I frikkin love numbers. Nice brain teaser...

Team Lazy

One more question for you all if you don't mind?

I'm a "bit" confused about running same size tires all around and its effect on the e-nannies.

Does it effect ALL cars, or have some people actually had some success with it? Reason being, if it's kind of a car by car basis, I can get a decent enough price on Pirelli slicks in 305/675/18.

And if I do have problems, do the problems go away with TCS etc turned off or else in Competition mode?

I'll hang up and listen to your answer

froggy47

Here is a link for rim size vs tire size.

http://www.tirerack.com/tires/tires....del=Ecsta+V710

Go to brands/tire model/specs

Q1) AFAIK GM diddled with the tc/ah spec from year to year and nobody that I know has DEFINITIVE information as to what the EXACT difference the tc/ah is happy with (baseline) it's generally a shorter front/taller rear. IF you start with the difference between the STOCK TIRES and KEEP that difference with other sizes you are OK. As you deviate from that & get closer to same size (all around) you invite tc/ah intervention. If you go taller front/shorter back you will get tc/ah to engage.

Q2) TC/AH off solves the "problem" in all cases that I know of. But your abs may take an issue with same size all around.

This is all for C5, not sure on C6. They have that plus the tire pressure nanny to deal with.

GT Racing Tires

305/675/18 up front will make the car handle for garbage. Too tall of a tire for the front.

davidfarmer

I agree that 675 is too tall, and I'd say 660 is probably the max for a front tire...but yes if you shut down the nannies completely, you should be able to drive the car.

kmagvette

I run the Pirelli D2 in 660 on all four corners, wheels are 18x11. The 675 up front may interfere with the bottom rear of the front wheel well. In my experience, the 675 on the rear of a stock 02 Z is not ideal at a track like Watkins Glen. The 660 allows you to just get up to redline in fourth gear before braking for the bus stop...the 675 seems to lug ever so slightly. That said, I would gladly run the 675 out back if I did not have access to the 660's...no way would I run the 675 up front.

Stock 02 Z?, well, the engine is stock...there might be a few suspension mods

0Anthony @ LGMotorsports

When you are looking at race tires, you need to find the actual specs of the tire. In some cases they may use the same mold for the tire so the listed size might be different but the tire is the same size. I believe that is the case with some of the Hoosier 335's and 345's when they are actually the same tire.


As for some of the race tires...you may see them listed as a 300-650-18 or 300-65-18 or similar.

This is not an aspect ratio in these cases.
First set is the width of the tire.. 300mm
Second set is height 650mm
last is rim diameter 18 inches.

So this would be a 11.8" wide tire, 25.6" tall on an 18" wheel.

Do note that some slicks are going to run on the wide side, and that is generally actual contact patch, not section width.

Team Lazy

Sh!tballs. All he has is 4 in that size, for $75 / tire. I was hoping they would be decent enough for some lapping until I can get the driveline back in the real race car or get something else more appropriately sized.

I guess I'll be lurking around the pits at the Mosport ALMS race like a crackhead looking for a fix. But more like a regular dude looking for castoffs.

Thanks everybody for the excellent tech.