[tomtom]

is there any other forum members that have tried this updgrade?
how much labour to do this upgrade?

[stressdoc]

There are many threads on sway bars and suspension tuning (search). Rear sways are a pain to install because you need to loosen the rear subframe to get room to wiggle the bars in and out. Not, repeat not, recommended as a novice or moderate DIY -- expect 2-3 hours shop time, and an alignment (maybe even a corner balance while you are at it).

In the way of a brief summary, the effect of a sway bar increases exponentially by the thickness of the bar. A change from stock ZSP 13 mm to 20 mm is huge. This will reduce the independent movement of the rear wheels. In a corner, the inside wheel will be much more prone to lifting off the surface, reducing traction. Given the power of the 335, this is not so good. Even with a LSD there is a balance that needs to be maintained among spring rates, sway bars, dampening rates, etc. And remember that what "feels" good -- e.g., reduced roll -- may not result in better overall handling and track performance. There are other ways -- e.g., going to a non-staggered tire set-up -- to shift the understeer/oversteer balance. There is a lot more to the M3 suspension than a thicker rear sway.

The addition of the M3 sway into the available options is great. At this point I would want to see how it works under a range of conditions and set-ups. Test, test, test!

[tengohambre]

If people are worried about 20mm being too thick, why not use the xi sway? 13 to 15 sounds reasonable. If the m3 is compatible with the xi, then the xi should be compatible with the other cars, right? Then again, my only reason for purchasing an OEM bar would be the cost, but it sounds rather expensive to install on our cars.

BTW, I swapped a m-coupe rear sway on my 318ti and it was a world of difference.

[ZJP]

I plan on buying the Hotchkis 16mm rear sway only and seeing how that works out.

[Fraggy]

Isnt the H&R rear sway 20mm?

[ECSTuning]

Yes, the H&R rear sway is 20mm and we do have those available as well.

[18LLC]

do i need any additional parts to fit the e90 m3 rear sway to e90 xi? such as bushing top and bottom, support, link, and different size screws?

[Mr. 5]

Originally Posted by tengohambre

If people are worried about 20mm being too thick, why not use the xi sway? 13 to 15 sounds reasonable. If the m3 is compatible with the xi, then the xi should be compatible with the other cars, right? Then again, my only reason for purchasing an OEM bar would be the cost, but it sounds rather expensive to install on our cars.

BTW, I swapped a m-coupe rear sway on my 318ti and it was a world of difference.

The reason being is because an XI rounding corners still has the front wheels propelling the car if the inside rear wheel lifts up. The M3's suspension is totally different and the M3 has an LSD.
If this happens to a non XI then you're gonna be screwed.
I went with the 14mm euro M sport bar.