Yet another 15" to 17" wheel upgrade thread

[gutowskia]

I have read a lot of posts about wheel fitment all stating different recommendations for various years and models. Without a definitive answer, I decided to take a scientific approach and try to figure out if I can upgrade my '87 300E with new 17" wheels with 37mm offset and 225/45-17 tires. The reason I'm trying to go with 225/45 tire is because it has exact same diameter as the original 195/65 and therefore should not have any impact on the speedometer.

Original wheels: 15" rim, 6.5" width, 49mm offset, 195/65-15 tires.
Potential upgrade: 17" rim, 7.5" width, 37mm offset, 225/45-17 tires.

I calculated the clearance between the strut and the inside of the rim to be 0.7mm smaller than with the original rim. Also, the rim should stick out 24.7mm further than the original. Here is my calculation:

1 inch = 25.4mm
49mm - 37mm = 12mm (center of the new rim is 12mm further out)

6.5" width / 2 = 82.55mm (distance center to edge of original rim)
7.5" width / 2 = 95.25mm (distance center to edge of new rim)

95.25mm - 82.55mm - 12mm = 0.7mm (inside clearance change compared to original)
95.25mm - 82.55mm + 12mm = 24.7mm (outside clearance change compared to original)

I calculated the clearance between the strut and the inside of the tire to be 3mm smaller than with the original rim. Also, the tire should stick out 27mm further than the original. Here is my calculation:

195mm / 2 = 97.5mm (distance center to sidewall of original tire)
225mm / 2 = 112.5mm (distance center to sidewall of new tire)

112.5mm - 97.5mm - 12mm = 3mm (inside clearance change compared to original)
112.5mm - 97.5mm + 12mm = 27mm (outside clearance change compared to original)

Since I have original suspension, the car is sitting rather high, so I'm not too concern about the outside clearance. My only concern is the new tire clearance on the inside of the front wheel. My current tire has only 6mm gap between the sidewall and the strut. The new 225 tire will have only 6mm - 3mm = 3mm gap! Wow, is 3mm too close for comfort? Any comments will be greatly appreciated.

Thanks,
-Andy.

[geordie]

With no rubbing problems.
Ive just installed my 3rd set of 225x45x17s
I've used Pirellis in the past but just changed to Pilot Sport AS s to try and get longer life.

[ksing44]

Since you did all of that calculating and measuring, you might be the kind of person that would appreciate the following reasoning. I think another aspect of fitment that will work in your favor is that your new wheels are 2� taller, which translates to 1� on either side of the hub. The front strut angles away from the wheel, so I think it is likely that the bulging portion of the tire will be located at an area of the shock that is farther away from the tire, even though the tire is the same overall diameter. Maybe that is why we rarely hear about rubbing on the inside with the bigger wheels. Rubbing on the ouside is the typical issue, but even that has not been an issue for many.

[gutowskia]

To follow up on my original query; I upgraded my wheels with 17" AMG rims and 225/45-17 tires. The front rims have 71/2Jx17H2 ET37 markings which I understand are 7.5" wide with 37mm offset. No problems at all on the inside or outside. In fact the new setup has a few millimeters of additional clearance between the tire sidewall and the strut. This is most likely due to the fact that the strut angels away from the wheel and the nature of low profile tires as Ksing44 mentioned. Thanks for your input!