Like it's already been said, 245/35/19FR and 275/35/19 is fine. Technically, if you're going from to 19's, a perfect fit would be a 255/35/19FR and a 275/35/19RR. That puts it at a increased height of .1in in the front and .3in in the rear. That's damn near close to stock. It would increase the front to back height of the car by .6in which I think would be a good thing. Although if your going from 18's to 19's the rears will have a decrease diameter of .1in however I really wouldn't be concerned with such a minute difference. Same goes with the 245/35 in the front. The overall diameter will decrease but only by .1in. Nothing to be concerned with. I am of the opinion that a 30 series tire is for a 20in wheel or larger under most circumstances and a 35 is a perfect fit for 19's (on the 350Z). I realize the isn't the gospel just a reference. I went from 225/50/17FR to 275/30/20FR and 235/50/17 to 285/30/20. Overall diameter for front and back is off by only .6inFR and .4inRR On a side bar, if the dealer didn't want to sell you friend what he wanted, I personally would of went somewhere else. It's the old addage, "If you don't take care of the customer, someone else will".

 

i know this thread was dead and buried, but i just had to clarify that it wasnt rdm wheels that screwed my friend, it was SPY ENGINEERING.

 

I had 245/35/19 and 275/30/19 when I had TE37s on my base Z. Didn't throw anything off kilter. Would've gone 275/35/19 but everything was sold out everywhere at the time. Technically, the closest match to stock is 275/35/19 rear. But there's a little bit more selection with 275/30: Yokohama AVS Sport, Continental SportContact, and Pilot XGT Z4.