Reply to "17" Tires: Options getting fewer & and your opinion on 285/40/17 size?"

I'd like to share two bits of experience:

When I installed the 18"/20" tire combo on 6018, the front tires were 245/35r18 (24.8" OD) and the rear tires were 325/25r20 (26.4" OD). The front tires had a slightly taller sidewall than the rear tires, 3.4" high sidewalls up front verses 3.2" high sidewalls in the rear. The 0.2" difference in sidewall was noticeable with the naked eye. And having rear sidewalls that were shorter than the front sidewalls didn't look right to my eyes. But my point has nothing to do with sidewall heights which would only be a consideration for someone using wheels that are 2" different in OD front to rear. My only point is that 0.200" differences in wheel/tire dimensions were discernible with the naked eye. This was unexpected, like you I didn't think such a small difference in dimension would be discernible. If the difference had only been 0.100" I don't think it would have. This is admittedly a minor point, I don't intend to be contentious in sharing this.

A major point is to keep the front/rear tires equally spaced within the fender arches while maintaining the proper chassis "stance" (i.e. a level chassis). When I purchased 6018 it was equipped with 245/40r17 front tires (24.7" OD) and 315/35r17 rear tires (25.7" OD). There was only 1" difference between front and rear tire diameter. To prevent the car having a "nose-up" attitude, and to correct the altered axis of the control arms, the previous owner (or the shop that did the work) lowered the front of the car on the suspension using the adjustable shocks until the chassis was level. The result was the front tires were no longer centered within the fender arches, instead the fenders sat "over" the front tires; i.e. the tops of the front tires were hidden up inside the wheel houses. It just didn't look right to me. This is why I warn about keeping the difference between front & rear tire diameter within 1.7" to 2.3".