What makes the M3 suspension so great?

[gadget]

I am not that knowledgeable in this area. Can someone please put the technical jargon into layman's terms and explain how the suspension varies from the 335 / e46 M and how it is better than other cars. Also what other cars have a similar set-up?

[swamp2]

Originally Posted by gadget

I am not that knowledgeable in this area. Can someone please put the technical jargon into layman's terms and explain how the suspension varies from the 335 / e46 M and how it is better than other cars. Also what other cars have a similar set-up?

It is not tremendously different that the 335i, but as they say the devil is in the details. Many of the suspension arms are forged aluminum opposed to cast aluminum or steel in the 335i. The susupension bushings are different materials, stiffer, sometimes maybe even rigid ball joint types in the M3. The suspension geometry is different based on the mounting points, pivot points and arm lengths. The result is different camber and caster as well as those being different along their travel. The struts on the M3 mount over a much larger surface area into a much beefier front hub assembly. Of course the springs are shorter and stiffer, the car is lower and compression and rebound damping are different.

[UltimateBMW]

And here is the legend you need to understand the back half of what Swamp posted:

Camber: Camber angle is the angle made by the wheel of an automobile; specifically, it is the angle between the vertical axis of the wheel and the vertical axis of the vehicle when viewed from the front or rear.
http://en.wikipedia.org/wiki/Camber_angle

Caster: A caster (or castor) is a type of wheel mounted with an offset steering pivot such that the wheel will automatically swivel to align itself to the direction from which it is pushed. They are commonly found on shopping carts and rolling chairs.
http://en.wikipedia.org/wiki/Caster

Damping: Any effect, either deliberately engendered or inherent to a system, that tends to reduce the amplitude of oscillations of an oscillatory system.
http://en.wikipedia.org/wiki/Damping

[GregW / Oregon]

Originally Posted by westwest888

I'm probably the only person in the BMW dealership who gets down on the concrete and looks under the vehicle. Having looked under my own car extensively, ...

Why not put it on a lift??

[GregW / Oregon]

Originally Posted by swamp2

It is not tremendously different that the 335i, but as they say the devil is in the details. Many of the suspension arms are forged aluminum opposed to cast aluminum or steel in the 335i. The susupension bushings are different materials, stiffer, sometimes maybe even rigid ball joint types in the M3. The suspension geometry is different based on the mounting points, pivot points and arm lengths. The result is different camber and caster as well as those being different along their travel. The struts on the M3 mount over a much larger surface area into a much beefier front hub assembly. Of course the springs are shorter and stiffer, the car is lower and compression and rebound damping are different.

Also, given the target demographic and reputation of the car, the tuning is more aggressive and higher preformance oriented. And, of course, we haven't even touched on EDC. All this involved lots of Nurburgring testing time.

[OzStriker]

We sooooooo need 335 and M3 underneath shots.

[GeriFix]

Originally Posted by OzStriker

We sooooooo need 335 and M3 underneath shots.

These aren't great (taken with my phone in the car park at work) but they show some of the differences in materials used (forged alloy in the M3 and steel in the 335).

335 Left Rear Assembly:


M3 Left Rear Assembly:


335 Differential:


M3 Differential (a work of art ):

[OzStriker]

Nice GeriFix!

I am not skilled enough to see if the geometry is unchanged or different but there is quite a contrast in materials there.

[GeriFix]

Originally Posted by OzStriker

Nice GeriFix!

I am not skilled enough to see if the geometry is unchanged or different but there is quite a contrast in materials there.

Neither am I Oz, but the M3 seems to sit higher on it's suspension than the 335. I would also like to correct Swamp2 .... the 335 is lower than the M3. From the outside the 335 is probably 4 or 5 cm lower at the roof line and it isn't as easy to get underneath as the M3!

[Epacy]

Originally Posted by GeriFix

Neither am I Oz, but the M3 seems to sit higher on it's suspension than the 335. I would also like to correct Swamp2 .... the 335 is lower than the M3. From the outside the 335 is probably 4 or 5 cm lower at the roof line and it isn't as easy to get underneath as the M3!

Yes, from the pictures I have seen the 335 sits lower.

[GeriFix]

Originally Posted by Epacy

Yes, from the pictures I have seen the 335 sits lower.

Actually, coming to think about it, part of this may be due to the tires. The run-flats on the 335 are a lower profile than the Pilot Sports on the M3. (BTW both cars above have 19" wheels)

[rvacha]

Originally Posted by GeriFix

Actually, coming to think about it, part of this may be due to the tires. The run-flats on the 335 are a lower profile than the Pilot Sports on the M3. (BTW both cars above have 19" wheels)

Ding! Ding! Ding! We have a winner in a round about way. The regular E9X series is tuned from the ground up for runflats while the M3 isn't. This affects everything from the spring rates to the sway bars to the dampers - and probably geometry as well