Originally Posted by
acidfast7
That's because in the US/NA, you run them at low speeds (below 80mph).
There's a noticeable difference in stability with wider tires and larger circumference above 120 or 130 mph due to the reduction in rev/sec reducing the perception of smaller defects from the wheel manufacturing process. Especially when the road surface is of high quality.
I'd love to see that BMW study because I don't believe what you're saying is true for the global market where speeds are higher and road quality is better due to lower environmental variation.
I will have to find the study but it recall that it was referring to the M series which now runs wheels as large as 22 inches and this is where the engineers found there was a reduction in performance, particularly in the handling department.
Smaller wheels do respond more quickly and will accelerate faster and the lower rolling speed of the larger wheel may have been where the issue arose, it was also noted that despite their testing the market has demanded these oversized wheels.
Maybe these are great when you can top out the car at very high speed but under normal driving they are detrimental.
Your 3 series BMW came with 14 inch wheels and when those rims and tyres are built to a very high standard this eliminates irregularities and better suspension technology can make up for a smaller wheel like it does on my Moulten bicycle.