A little background on my car:
I had previously install KW V1 coilovers on my 07 335 and really liked the setup. But the more I drove the car I realized that something was off.; nothing major, but the car was twitchy and I attributed it to the very small rear sway bar. The 335 comes with a 26.5 mm front sway bar and a 13mm rear. The oem rear sway bar can be mistaken for a brake line; it’s tiny! I’ve seen Honda Accords with bigger rear sway bars!
Anyway, I did some research and the aftermarket sway bars (Hotchkis and H&R) are really expensive so I started looking at the oem M3 sways. The M3 has a 26.5mm front sway bar and a 20mm rear sway bar. Those sizes are very close to the aftermarket sway bar kits. The bushings are also much stiffer than the stock 335 sway bar bushings due to their makeup which is rubber coated steel bearings. The front and rear sway bars, bushings and clamps run ~$310 before shipping from Faulkner BMW in Pa. Most aftermarket kits are near $400 or more. Part numbers can be found on realoem.com. I can post them here if anyone is interested as well.
Also, the E90 M3 Convertible runs a 23.5 rear bar, but I did not want to go this extreme as I wanted to keep the car balanced. I noted this for anyone who is looking for something more extreme. The cost is the same as the non-convertible rear sway bar.
Now to the install:
The front bar is very straightforward and does not take much time (approx 45 mins). Why change the front when they are the same size you ask? Well, the stock 335 front sway bar has a taper in two spots and the M3 sway does not. The taper affects the bar’s affective rate. Also, the M3 bushings are rubber coated steel bearings, not just rubber bushings like the 335 bar uses.
The rear sway bar is a giant m*thaf*ker. Basically you have to lower the entire rear subframe and exhaust to make room to fish the bigger M3 sway bar into place. Probably took 2.5 hours to do but could be done faster now because of lessons learned. Basically, any suspension work in the rear of the 335 is a PITA.
Fitment for front and rear is perfect.
Driving impressions:
Wow! Much better, this is the way the car should have come from the factory. Huge improvement in the rear and the understeer is minimized. 7mm makes a noticeable difference. There is a bit more “road noise” but nothing that could be considered annoying.
Overall, I’m really happy with this upgrade even though the install was draining.
Here are some comparison pictures of the stock 335 rear sway bar and the stock M3 sway bar that replaced it.
