Quote:
Originally Posted by solstice
It can with different tire profiles but again he did state the larger contact patch as an explanation to why they had staggered wheel sizes.
They wanted more contact patch and likely tried all options as wider wheels, more profile at the same wheel size and larger wheels and the best overall results were achieved with larger wheels.
I don’t think the main target was a lower profile rear tire instead it was a larger contact patch. The sidewall was likely just tuned as a secondary parameter.
For the G8X we haven’t gotten a detailed explanation to why it ended up were it did. Your guess is as good as any. I think mkoesel is close to the truth that this is more an empirical result of testing than a formula based decision.
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I haven't watched the video and I am no expert, but this is my take on it:
The increased contact patch from increasing diameter is minimal. Tire width is what actually effectively increases contact patch (and in turn the wheel width to accommodate the tire). But with an increased tire and wheel width, comes an increase in rubber, which increases tire deflection on load at a given tire pressure. This gives more grip but sacrifices responsiveness as
CanAutM3 pointed out. To help balance this out, we can use a bigger diameter wheel to decrease the tire sidewall which will decrease deflection but maintain the contact patch. So no, WHEEL diameters do not increase contact patch, but they can allow for a wider tire without excessive tire sidewall.
Additionally, having a larger overall diameter wheel/tire combo changes the overall driving ratio of the car. A larger tire means a higher
potential speed. I don't know if the G80's rolling diameter will be more than the fronts because I am too lazy to look up the tire sizes, but that would be one potential reason for using a larger rear wheel.
These arguments about the increased weight of larger rear wheels are kind of ironic given BMW increased the weight of the G80 by increasing its size, which isn't as correctable as new rims.