[priapism]

Got an E91, it understeers a fair bit on track. I was considering upgrading the rear sway bar to balance the handling out a bit.

What size is the factory rear bar? Is it different than the regular e91, given that it's an M-sport?

What are my options for a mild / moderate upgrade in the rear?

I'd rather not go with stiffer springs as the roads here are absolutely obliterated. I'll deal with some body roll, that's fine, but I'd like to dial out some of that understeer a little.

A better solution to this problem is to add more negative camber up front.

What are your current alignment specs?

[priapism]

Oh is it adjustable? I just went with the factory specs when I aligned it, didn't know front camber was adjustable on these. I'm used to my e30...

Barely adjustable...you'll need some relatively inexpensive parts to get the rest of the way there. All worth it, especially if you're tracking the car; a prerequisite if you ask most, actually.

[priapism]

What parts? I see that it's adjustable for ~1 degree from the factory, which isn't much but it's something.

[tlow98]

Pull the alignment pin on the top of the strut tower and then add something like the Dinan camber plate. -1.5ish for both I think (?)

Another addition if you still need more would be the M3 lower control arms. They'll get you another -.7 on top of the above.