i just buy rota grid wheels in 15x8 all.

what is the recommended tires size?

my 240z have no fender flairs and i don't want to cut or touch the fender wall clear out.

225/50R15 for the widest, may have slight rubbing. 205/55R15 no rub, taller sidewall.

Selections on 225/50/15 get slimmer by the year - you may have to look at something else.

 

205/50x15's look very good on a lowered car. One of the more popular sizes as well, so lots of choice.

What will the car be used for?  If it's just a daily driver, a 205 will be good.  Racers use 225/50R15 or 225/45R15.  The diameter gets small though so the car gets much lower than stock.

I recommend 205/55R15 if you want to be safe and fill the wheel wells.  As HaZmatt stated, you may have rubbing issues with a 225/50R15.

Both sizes half slim choices for tires. You can get either okay-but-not-great summer tires or aggressive street/track tires. I'd go for the latter but it depends on what you use your Z for...