[bbnks2]

Swapped in an M3 rear-end this past weekend.

The M3 rear bar is hollow. Aftermarket bars all claim to be stiffer than the stock E92 M3 sway. Some adjustable bars do claim to be pretty close to equivalent to the stock M3 bar in effective wheel rate when set to their softest settings though. I am not sure why people said earlier that their aftermarket bars are much less effective than the "massive" (and hollow) M3 sway not to mention its tabs are not straight which makes it even less effective.

The stock bushing on the M3 sway are designed to BIND the rear bar. This means that the M3 bar is also contributing to the effective wheel rate during acceleration/squat since the bar cannot rotate freely. While the M3 bushings do allow quiet a bit of deflection, I bored them out a bit before installing the rear end so that the bar can rotate completely freely without "wind-up." Same deal with my stock front bar, I had to un-glue the stock front bushings so that the bar was not contributing to the effective wheel rate under braking compression. If your sway bars are binding you have to consider their effect on wheel rates in times other than roll.