Quote:
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.
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Considering that the overall diameter of the 275/40/19 was 26.5 inches and the overall diameter of the 295/35/19 is 26 inches... not as noticeable as you're claiming
The front 245/40's was 26.7 and the 255/35's are 26.1, a bit more than the rears, but still not as noticeable as you claim.
Don't forget that while he did decrease the aspect ratio he also increased the width, which makes the change to overall diameter not as dramatic.
Also, just out of curiosity what size tire do you think he should have changed to? There aren't exactly a ton of options for changing tire size to a wider tire while maintaining the exact same overall diameter. It's only going to be "close".
And to keep the thread on track... here are some shots of my "meaty" tires
285/35/19's ... up FRONT and 305/30/19's in the rear
