370z MEATY TIRE THREAD

[cjr1881]

Originally Posted by Nissanboy

wrong size? that's like a perfect combo, both side walls from front to back are about the same size.
and please enlighten me on how it will screw up the gearing, didn't know tires changed your gear ratio

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.

[FortuneLSX-TT]

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.

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

[cjr1881]

yeah, you're right. I plugged in the wrong numbers (only like -3%), but still... I would never go less. Your tires are a much better fit. I'm getting some meaty tires soon and I'll have some pics up. 20" Toyo R888 285/315

[daisuke149]

Originally Posted by cjr1881

yeah, you're right. I plugged in the wrong numbers (only like -3%), but still... I would never go less. Your tires are a much better fit. I'm getting some meaty tires soon and I'll have some pics up. 20" Toyo R888 285/315

based on your previous comments..

a 315/25/20 is smaller than OEM and so by your own words you shouldnt. but I think the r888 comes in 315/30/20 which would be taller than OEM.
a 285/30/20 for fronts is about perfect to oem though

[cjr1881]

Originally Posted by daisuke149

based on your previous comments..

a 315/25/20 is smaller than OEM and so by your own words you shouldnt. but I think the r888 comes in 315/30/20 which would be taller than OEM.
a 285/30/20 for fronts is about perfect to oem though

Yeah those are the only tire options in 20" and they are just fine. I would rather go taller than smaller with performance upgrades I want first gear to be useable. 285/35/20 315/30/20

[FortuneLSX-TT]

Originally Posted by cjr1881

Yeah those are the only tire options in 20" and they are just fine. I would rather go taller than smaller with performance upgrades I want first gear to be useable. 285/35/20 315/30/20

315*.30= 94.5mm sidewall
20*25.4= 508mm rim
508+94.5+94.5 = 697mm overall diameter (27.44in)

vs stock
275*.35=96.25mm sidewall
19*25.4= 482.6mm rim
482.6+96.25+96.25=675mm overall diameter (26.57in)

You're increasing your rear overall tire diameter by almost an inch.

315*.25= 78.75 mm sidewall
20*25.4 = 508mm rim
508+78.75+ 78.75 = 665.5 mm overall diameter (26.2in)
The 25's drop about .4in from stock whereas the 35's add almost a full inch in those sizes.

If I was going for 20's I'd go with the 25 and not the 30, but good luck. I think first gear will still be usable in either size, but like others have said... much taller than stock. I'd be interested to see how it looks and how far off your speedo is and if you have any rubbing issues etc.

[cjr1881]

Originally Posted by FortuneLSX-TT

315*.30= 94.5mm sidewall
20*25.4= 508mm rim
508+94.5+94.5 = 697mm overall diameter (27.44in)

vs stock
275*.35=96.25mm sidewall
19*25.4= 482.6mm rim
482.6+96.25+96.25=675mm overall diameter (26.57in)

You're increasing your rear overall tire diameter by almost an inch.

315*.25= 78.75 mm sidewall
20*25.4 = 508mm rim
508+78.75+ 78.75 = 665.5 mm overall diameter (26.2in)
The 25's drop about .4in from stock whereas the 35's add almost a full inch in those sizes.

If I was going for 20's I'd go with the 25 and not the 30, but good luck. I think first gear will still be usable in either size, but like others have said... much taller than stock. I'd be interested to see how it looks and how far off your speedo is and if you have any rubbing issues etc.

There is no /25/20. He made a typo, those are the only tires available in 20". I used an offset and tire calculator and it says I will be doing 62 when my speedometer says 60. 2.8% I think it said. I don't have anything to consider because there are only 2 tires made in R888 20" - 315/30 285/35. If anyone knows of any other competition 20" tires I am all ears. I think maybe michelin, but I hate them. Other than that, I don't know of any other tire company that makes 20" competition DOT tires.

[KaienZ34]

Originally Posted by cjr1881

yeah, you're right. I plugged in the wrong numbers (only like -3%), but still... I would never go less. Your tires are a much better fit. I'm getting some meaty tires soon and I'll have some pics up. 20" Toyo R888 285/315

The real question is what profile will you be running??

[whoady4shoady]

Originally Posted by FortuneLSX-TT

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

How is this setup "285/35/19's ... up FRONT and 305/30/19's in the rear" for autocross on the stock nismo rims? I was thinking of going with a square set up of 285/35/19 on swift springs for autocross. Hummm......

Do you have any rubbing issues with 285/35/19 on the fronts?

[blacknismoZ]

With 285/35/19 up front any rubbing or fitment issues?

Originally Posted by FortuneLSX-TT

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

[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

[Nissanboy]

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.

17-18%?!??! What are you smoking?
@ 60mphs, his speedometer will be off about 1 1/2 mph, resulting 61-62 mph

Do the math Tire size calculator