View Single Post
      04-16-2019, 11:23 AM   #42
ApexWheels
BimmerPost Supporting Vendor
ApexWheels's Avatar
1417
Rep
2,650
Posts


Drives: M3
Join Date: Jun 2012
Location: Bay Area

iTrader: (2)

Quote:
Originally Posted by Derkluge View Post
Are there any wider-than-stock tires - but with a stock aspect ratio (i.e., 35) - that would work on these wheels, assuming the car has a stock suspension? (Something like F:255/35/19; B:285/35/19?)
Keep in mind the definition of an aspect ratio. Aspect ratio is the ratio of the height of the tire's cross-section to its width. For example, in a size P245/35 R19 tire, the 35 means that the height is equal to 35% of the tire's width. The bigger the aspect ratio, the bigger the tire's sidewall will be.

Here is the important part that many forget. As you increase tire width over stock, the aspect ratio should naturally decrease in an effort to keep the rolling diameter as close to stock as possible. In other words, a 35 aspect ratio and a 30 aspect ratio can actually be close or equivalent in sidewall height at the appropriate respective widths. If you kept the same aspect ratio with a substantially wider tire, you would end up with a tire/sidewall that is much taller than stock - this would quickly lead to issues. Often times the wider tire is slightly shorter, but still very much acceptable.

Example

Stock front tire - 245/35-19 = 25.75" tall
Correct aftermarket front tire - 275/30-19 = 25.5" tall
Difference in diameter = -0.25" or -1%

vs.

Stock front tire - 245/35-19 = 25.75" tall
Incorrect aftermarket front tire - 275/35-19 = 26.58" tall
Difference in diameter = -0.83" or 3.1%


If you only increase the tire widths by one size over stock, 255/35-19 front and 275/35-19 rear, you can get away with running a 35 aspect ratio as the increase in height over stock is nominal. The popular Bridgestone RE-71R's come in these sizes, so I have a feeling many enthusiasts will try these out with our wheels.

Stock front tire - 245/35-19 = 25.75" tall
Correct aftermarket front tire - 255/35-19 = 26" tall
Difference in diameter = 0.27" or 1%

Quote:
Originally Posted by Megator View Post
Any suspension work to fit that square setup? and what ET did you choose?
Quote:
Originally Posted by cntzl View Post
They are ET35 so front requires 12mm or bigger spacers. I run -3 front and -2 rear camber. Also, the car is slightly lowered on Ohlins.
The EC-7 18x9.5" ET35 square setup that cntzl is running only requires 5mm spacers up front to clear the stock suspension along with a wide variety of aftermarket coilovers. With that said, coilovers known to compromise inner strut clearance like KW and Ohlins will require thicker spacers. Those suspension designs just eat up a lot of inner clearance.

- Ryan
__________________

Last edited by ApexWheels; 04-16-2019 at 11:31 AM..
Appreciate 1