hello, I have a Enthusiast Roadster, and it came with the 17" wheels,
I now want to upgrade to the OEM 18" wheels, what tire size that are factory size suppose to be. I do not want to make my speedometer be off my a few mph. thanks,,,,,remember I'm a newbie.....thanks

 

When you go to buy your wheels and have them put on they will be sure to keep your total diameter the same.

 

if you get the Nismo wheels (18") you can install the recommended tire size, F: 245/40/18 and R: 275/40/18.

good luck!

 

Look in the owner's manual, it has lots of info.

 

Factory sizes for the 18s are 245/45/18 rear and 225/45/18 for the front....I have an '04 ZR and just put Michelin Pilot Sport AS 255/40/18 rear and 235/45/18 up front...GL2U....Dave p.s. The OEM Bridgestones suck...11,000 miles...:-(

 

If you are going to upgrade to 18" wheels, why do you want to stay with the heavy, narrow OEM 18" wheels. For the same money or just a little more, you can upgrade to MUCH lighter, better wider wheels/tires. Even if you have concerns about aftermarket stuff, you can go NISMO. Their wheels are one of the lightest and highest quality available for the Z, fits perfectly and can accomodate 245f/275r width rubber which will increasing your handling limits by light years.