370z MEATY TIRE THREAD

[Ron]

Originally Posted by cjr1881

You need to keep the total circumference of the tire the same or you will change your gearing. He has effectively shortened his gearing and will now take more rpms to achieve the same speed. The profiles for 19" tires on the 370Z should be front/40/19 rear/35/19. His are F/35/19 R/30/19 . When his speedometer says he is doing 60mph, he will actually be doing about 50mph. 17-18% off. I can't believe how many cars I see with the wrong profile tires. People are obviously oblivious to the fact that they are not just changing how the tire looks. If you plus size you need to change aspects accordingly, and if you keep same wheel size then you must keep same aspect or you will be changing gearing and your speedometer.

so u are saying that no matter how wide said 19'' tires are you should always go with 40 front and 35 rear for side profile?? You do know that those numbers are directly proportional to the tire's width, right?

305/30/19 means sidewall is 30% of 305mm.
285/35/19 means sidewall is 35% of 285mm... etc etc