[Pete_vB]

So I'm beginning to dig in here, I'll post what I'm finding as I go along. If someone spots an error please jump in and let me know.

It's interesting to see how BMW altered our cars vs the M3.

This is based on googling so I'm not sure of the source, but I'm seeing M3 spring rates quoted around 167 F and 550 R- they are progressive like most modern setups, so in reality this would be an average. Motion ratios are quoted at .96 and .57, so wheel rates would work out to 154 F / 177 R. It's a little unusual for the rear to be higher than the front.

The 1M, on the other hand, was quoted at 230 F / 550 R, wheel rates of 212 F and 177 R. So it appears BMW stiffened the front spring rate up significantly for the 1M. I think they left the swaybars alone? So that would result in more mid corner understeer, but ability to put a little more power down out of the corners.

On the shocks, it looks like they went the opposite direction. The front shocks look like they are similar to the M3s despite the stiffer springs, while the rear shocks have been stiffened up to be on the stiff side. Compression to rebound ratio looks very similar to the M3.

If we assume the above is true and take the changes as a package, we might hypothesize that BMW was trying to add stability- the higher front spring rates would promote understeer and hence stability mid corner. On corner entry, however, that would result in poor turn-in, so higher rear bump and rebound forces transfer weight faster at the back, counteracting this and promoting quick turn-in. The increased rear bump might also help put a little power down on corner exit, a good thing given the 1M's torque.

I wonder, however, how this strategy, which depends on the rear running more damped than the front, would work over bumps?

It's a work in progress, but interesting. I don't have much of the data I'd need to do a proper analysis- I'm leaving bump stops out, assuming linear springs, guessing at swaybars, toe curves, roll center heights, etc. I still hope some trends pop out, we'll see.