BMW M Coupe and Roadster (Z4)

FAST

FACTS

Between the Coupe and the Roadster, the Coupe is slightly more hardcore, with a quicker steering ratio, stiffer springs, and more aggressive shocks. The Coupe’s chassis is also much stiffer, and the fixed roof adds only 11 lbs to the Roadster
The Z4 M carried the DOHC S54 engine from the E46 M3, although a shorter and more restrictive exhaust system was required for fitment in the Z4
The Z4 M couldn’t use the M3’s 6spd, however, because it wouldn’t fit. BMW instead used an all new “Type H” ZF 6spd for this car
The Z4 M also used a different engine management system, known as MSS70. This system, capable of 64 million calculations per second, was superior to the one used in the M3 (MSS54 – 25 million per second)
The Z4 M was basically a small roadster version of the E46 M3. It shared the same rear subframe, limited slip diff, front control arms, and the same Continental ContiSport Contact tires. The brake system, consisting of aluminum hubs, stainless steel pins, and cross drilled/vented floating brake rotors are straight from the M3 CSL
The electric power steering system used in the rest of the Z4 line was ditched for a hydraulic power rack and pinion steering, for superior steering feel. The Z4 M actually has a quicker steering ratio than the already quick steering of the M3 CSL (14.5:1 CSL vs 13.7:1 M roadster vs 12.8:1 M Coupe)
An “M” Coupe version of the Z4 was never planned, due to poor sales of the Z3 M Coupe. However, it became a possibility once the engineers proved they could keep costs down by sharing many parts with the E46 M3 and CSL. In addition, the board loved the look (and extra performance), so the M Coupe was given the green light

Key Model Year Changes:

2006 marks the first year of production for the M models
2007
Tire Pressure Monitoring in each wheel (beginning 10/06 production date) is now standard Hexagon interior trim replaces brushed aluminum) HD radio becomes available (03/07+ production date)
2008
'08 models receive an AUX input for the sound system Engine mount hardware is upgraded after 3/08 production date