But you're putting them on a Z33, yes? For 18s on a 350Z, you will use either:

225/45-18F & 245/45-18R - That's OEM sizing. (FWIW, you're correct that the 370Z Base model takes 225/50-18 but we're talking different cars with different tire requirements.)

Optional (NOT factory optional, user optional) on the 8/8.5" wheels (on 350Z): 245/40-18F & 245/45-18 OR 265/40-18R

 

Thanks MicVelo! OK that makes sense to me now. I'm surprised to find out that the rear tire is supposed to be about an inch taller that the front tire but I guess it was designed that way for a reason. Thanks again!

 

Suspension was designed for very fast reactions and reflexes. Staggered setup on the Z was designed - and this is mild speculation - that the car was designed to give a neutral-to-modest understeering attitude to keep inexperienced drivers out of trouble by preventing or at least slow down tail-out oversteer (hence a spin).

The car's ECM is programmed to read the wheel speeds F and R and when/if it detects that one end's (or particular) wheelspeed is higher, it knows to invoke traction control or VDC (on cars so equipped) because said wheel is presumed to be spinning and has lost traction. <====very simplified description. The ECM knows that the front tires are shorter and adjusts for the difference in diameter F to R. That's why its important to maintain the same ratio in diameters F to R. That is, the rears are always taller than the front by roughly 3%. If you go outside of that 3%, say, by buying tires too short or too tall on one end, you'll run into the persistent "SLIP" light indicating that VDC is being triggered and you will have no engine power as the control module will constantly cut power to reduce what it sees as "spinout conditions".

370Z has different parameters because the tires are close to the same diameter but operates in the same manner. But on the Z34, the ECM on that car is "tuned" differently; that is, that car is expecting even wheel speeds in normal conditions and therefore has different triggering points for either traction control or VDC than a Z33.

 

I almost didn't ask about the tire size because I hate to wear you out with questions - but now I'm glad that I did. You kept me from making another mistake. Thanks again!

 

Dude this post makes me so happy. I just bought these exact wheels for my BLACK 2007 350Z. I have always loved the look of these rims and since I wanted an extra wheel set for autocross, it was a win win. Your pictures show what my car will look like, and I LOVE the result. Everything is black on my car, so I thought about blacking the wheels out, but after seeing them here, I have second thoughts.

 

Hey I know this post is old, but I really appreciate you posting this. I just bought these exact wheels for my BLACK 350Z, so now I get to see them in action before I get them! I needed a set of track rims, but after seeing yours I think these may become my daily drivers and my old ones will become the track rims. I even thought about blacking them out since my Z is all blacked out, but I really dig this look. Thanks!