I measured the outside wheel lip - they are about 19.5" Of coarse the tire mounts below this point. Is that what you wanted?

 

I think he means the outer tire diameter.

Front 225/45R18 are ~660mm
Rear 245/45R18 are ~680mm

 

All the the Z VDC cares about is the speed of each wheel and that there is still understeer in the car, so as long as the overall tire diameter is not changed, the Z is happy. This goes for the ABS as well.

 

Yea - I asked him that - he specifically asked for the 18" wheel diameter.

 

Just read back, and yes, I did ask the rim diameter. My mistake. I'm looking for the overall tire diameter from a Track model 18" rim with stock tires.

Thanks guys!

 

mooddude.....to expand that comment, I believe that it's not just the diameter, but the difference in diameter between the front and rear wheels should not exceed a critical value which I can't remember right now. I go from 17 to 18 to 19's with no issues because it's the relationship between the front and rear wheels that matters.

-Steve

 

Yes - you got it right. The VDC is measuring the difference of speed between the front and rear tires (and left and right, but lets hope no one is putting a different size tire on those - unless you are racing NASCAR and I would hate to see a Z do that ). So if you go smaller tires - you just got to ensure that you maintain the right ratio.

 

Cool. The diameter of my tire wrapped around the 19's are the same. Seems to be exactly the same but it's kinda hard to get an exact measurement w/ the car sitting on the tire. Sucks I never got to drive my car with stock track rims and tires. Searched and found the track model rims are 18lbs each. Tires maybe 25-26lbs each? Anyone wanna take a shot at this?? I'm sure I've got several extra lbs on each rim/tire...

Thanks guys.

 

Tirerack publishes the weight of all the tires they sell. Take a look and pick your tire and size and then you can figure out your exact weight.