Originally Posted by swamp2
I agree with many of your guesses/statements above but this one below is almost for sure incorrect.
The engine will have much more torque and this will require stronger components in much of the driveline. Without very expensive composites stronger generally means heavier.
Wheels: Existing wheels are quite light. New car may get 19" standard and 20" optional. From the base 18" wheels this would also likely be a weight increase.
Suspension: Without advanced and very expensive use of composites it will be challenging to save much weight compared to the existing cars forged aluminum parts.
The existing CF roof itself is very light and not even a structural component (which contributes to its already low weight).
I agree BMW is going to press very hard to control, manage and likely to reduce the weight of the new M3. It just is most likely not going to come from the areas you have mentioned.
Those changes will be coming and are being tested. The 18 wheels are not even forged now so how can you say that they are light as they can be? Brakes will be larger and lighter and have a CF option.
The driveshaft/ prop shaft can lose weight and get stronger as can the half shafts. They are in the prototypes and other brands are already using this technology in less than super car price points (Even the M5/M6 are lighter than the one's they replaced)- the Rear diff was originally designed to be used with these components.
They are making suspension bits out of CF and testing it now, and using more aluminum in areas that were once steel. The aramid/CF sandwich is lighter and stronger than steel and will be used in non-visible areas where necessary to lose weight and add rigidity.
They are doing this and a lot more. I heard this from a top executive on more than one occasion. The price BMW is getting CF for is cheap compared to others- they are running the show now thanks in small part to the BMWi ramp up.
What will make it to the street- no one knows as they are still testing durability and wear on these components. Biggest concern with the CF is not it breaking but it forcing added stresses to other areas, computer modeling can only do so much.