Why do some sports cars like NSX & 350Z use 18" Front and 19" rear rims? What are the benifits? Can we do it on our Lexus?

 

Some do it for looks, some do it for performance reasons.

The only performance reason I can think of is you have so much fender room in the back, but you don't want to run a thick tire, so you ramp up the diameter of the wheel so you can run a low pro tire.

You can do it on your Lexus as long as you keep the rolling diameter the same and you don't rub.

Honestly if you're going to get new wheels though, just run staggered width, not heights.

 

I can't speak for other cars, but for the NSX, it originally came with 15" front and 16" rear. It later was updated to 16" front and 17" rear, and only in 2002+ it went to 17" all around. Orginally it was done because the smaller diameter front rim not only gives better steering response compared to a larger rim, but the location of the front fender well in relation to the cabin meant they wanted to keep the fender well as small as possible. For anyone that owns an NSX they know that the front fender wells are rather small and shallow. Even when I ran aftermarket rims I ran 7.5" front compared with 10" rear. Anyway, I'm sure there is more to it, but that is just some of the things I've read about the NSX reasons.

To address your specific question, the reason why NSX owners continue to use a staggard diamter front to rear is to keep the same ratio as stock to keep the traction control system and ABS system working properly. Why others put staggard diamter rims on cars that didn't come with staggard diameter rims stock is beyond me though.

 

The 2006 Nissan 350Z Track model comes with 18x8 front and 19x10 rear. All others get 18". There has to be a performace reason for that. Anyone know?

I want to do the same on my IS350. What do you guys think?

 

Don't do it.

 

Not recommended. If the 350Z Track comes with different size wheels front and rear, then that means the engineers designed it that way, and calibrated the tire pressure sensors, odometer, speedometer, ABS, traction control, stability system, etc..... to compensate, as all these are based on wheel rotation speeds.
If for some reason you don't like the factory wheels and tires, you of course can replace them....but if you do, it's best to stick with the same size the car came with....or at least a combination that gives you the same outside rolling diameter.
Even doing this, though, you may lose the tire-pressure sensors if you no longer have factory wheels.

Many of the problems that CL members have with their cars, and requests for help and advice, are due to the negative effects of trying to out-do the factory on wheels and tires.