[E90ALLMANUAL]

Current set up
E90 328i, sport package, manual trans
Front Whiteline 27mm sway bar
Front upper and lower M3 arms
Whiteline rear subframe inserts(best mod so far
17x8 with 225/45/17 Dirrezzas
I use the car for autox and track days.

I have a rear sway bar from an E92 M3 to be install at some point. I know is not recommended to upgrade the rear sway bar with an open differential because it will increase inside tire wheel spin. But I think the e-diff should help with that.

So, should I do it?

I don't really care about be competitive or legal for Autocrossing.

[mlifxs]

I have some similarities in my setup and I've asked myself the same question.

sport package, M3 arms front and rear, 27mm H&R front bar, square tire setup (245s), bmw perf dampers, Dinan springs, whiteline inserts.

I have a 15mm xi bar sitting in my garage, waiting for install, but I just can't bring myself to doing the labor, as I think I'll be unhappy with the results.

At autox, I can easily push my car hard enough to bring the tail out. On the street, I can feel DTC fighting to keep the rear in line when I push hard....so I'm thinking going from 13mm to 15mm is a bad idea without LSD or some other change in the rear to help with traction. Maybe some smart, credible suspension guru can change my mind, but otherwise, no for me.

FWIW, here's what Dinan says about their 15.8mm rear bar:

"Only recommended for non-xi vehicles if equipped with D120-0530 28mm Front Swaybar, and one of the following: Limited-slip differential or rear tires that are wider than the front tires by 20mm or more."

[Cloud9blue]

Rear sway without LSD is a bad idea unless you plan on drifting this car

[dbworld4k]

I have a M3 rear sway bar and I loved how tight it made the rear end to throttle inputs. I also have a LSD, M3 front and rear arms and coilovers though.

[E90ALLMANUAL]

Originally Posted by dbworld4k

I have a M3 rear sway bar and I loved how tight it made the rear end to throttle inputs. I also have a LSD, M3 front and rear arms and coilovers though.

Did you installed all the parts at the same time?

[CALWATERBOY]

Originally Posted by E90ALLMANUAL

So, should I do it?

You should not.

Dude, save your pesos for THIS, after which that M3 sway'll work it's magic....e-diff just don't got the right stuff.

[avocet]

I have a sport package 328 with a 30mm front hotch bar and a 20mm rear h&r. I love the set up. With the stock or hotchkis rear my car had dreadful understeer. I am running oem size staggered 19's.

With 328 power an lsd isn't as critical for potential traction issues causing your inside wheel to spin during high power/high weight transfer corners.

If your set up is balanced a larger rear bar will be fine.

If you also have stiff(er) springs your increased roll stiffness might add to the tractuon issues...

[dbworld4k]

Originally Posted by E90ALLMANUAL

Did you installed all the parts at the same time?

I had the rear sway bar and LSD installed at the same time.

These tightened up the rear end for me and the car felt much more alive as whole unit instead of just a tighter front half when I had just the front sway bar.

[neoduffer]

I would go with a wider tire, like 245 wide Bridgestone RE71 instead. The labor alone for the rear sway bar install will cover the majority of the cost for new tires. Camber plates to maximize front camber will help as well to get you into the 2.0 to 3.0 degree negative camber range will provide extra cornering grip up front. Dinan camber plates for comfort since these reuse the top hats or Vorschlag or Ground Control for a firmer ride are the usual suspects.

Stiffer springs will help with roll stiffness when cornering, plus manage forward and aft pitch from braking and acceleration. Swift R springs will work with stock dampers if you want to avoid coil-overs.

Basically, there are more bang for your buck things to do before the rear sway.