I plan on getting aluminum (for weight) 19 inch wheels. How much slower will my Z be by upgrading from factory 17s?

 

Not really noticeable. Just add an intake or cat back exhaust.

 

Yes, but chances are you won't notice it unless you time it at the track or strip. Unless you buy lightweight wheels and tires, you are increasing the weight and hence the rotational inertia of each wheel. That takes more power to get them up to speed so you will be a little slower. The extra weight can also affect the ride and handling.

 

It will be slower! I lost 20hp going from 18" oem to 19" volk gt-c, on the same dyno. This is back i the day when I was NA, now it doesnt matter 1, and second are useless on the street, that why I dont street race , only Interstate racing

 

How much is much? Races, like the one above, are won buy 1/100 seconds. 1/100 seconds may not be much, but its a WIN and thats all that counts. 19 inch wheels are not for performance. Its the bling that counts. So go 19 or 20 inches.

 

I have not noticed my Z being any slower than with the stock 18's I had before.

It hauls a$$ on both counts.

 

Would you notice a 1/10th second in a quarter mile run? Would you notice two or three seconds out of a 90 second loop around a road course? Probably not but there is a definite performance hit.

The place where I noticed the greatest difference in performance is gas mileage. I lost about 2 mpg going from 18" to 19". It's not from what you think though as my 19" wheel/tire combo is 10lbs lighter than the OEM wheel/tire. The loss is due to the increased rolling resistance of the wider tires I went with. As you can see, everything has its price.

 

10 Mph

 

You will need to downshift more to get uphills

 

I ran my buddy after he got his 19s on and from a 1st hear roll, I gradually pulled about a car length up to about a 100 or so. With his stock 18s, we were even from any type of race.