E85 M Roadster
  History
Production Data
Drivetrain
Chassis
Cosmetics
Special Versions
Colors and Upholstery
   
 
Production Versions:
BT91: European-spec (LHD), 01/2006 through 07/2008
BT92: European-spec (RHD), 01/2006 through 07/2008
BT93: North American-spec (LHD), 02/2006 through 08/2008
   
History
What makes the E85 M Roadster unique?
The E85 M Roadster is the flagship model of the E85 Z4 roadster line and was developed by BMW M GmbH, the high-performance subsidiary of BMW AG. It features the 3.2-liter S54 inline-6 powerplant first introduced in the E46 M3, as well as an enhanced chassis and many special cosmetic alterations that are unique to this model.
Where was the E85 M Roadster introduced?
The E85 M Roadster made its world debut at the 2006 North American International Auto Show in Detroit.
Where was the E85 M Roadster produced?
Like all E85 (roadster) and E86 (coupe) Z4 models sold worldwide, final assembly of the E85 M Roadster took place at the Spartanburg, South Carolina factory. However, its entire drivetrain was produced in Germany and mated to the car at Spartanburg.
Production Data
How many versions of the E85 M Roadster were produced?
BMW M offered three distinct versions of the E85 M Roadster: European-spec models in both left-hand drive and right-hand drive configurations, plus a single North American-spec version.
How many of each version were produced?
BT91 (ECE-spec, LHD): 1,425 produced from 01/2006 through 07/2008
BT92 (ECE-spec, RHD): 921 produced from 01/2006 through 07/2008
BT93 (NA-spec, LHD): 3,041 produced from 02/2006 through 08/2008
What changes were made to the E85 M Roadster during its production?
Very few changes were made to the E85 M Roadster during the less than three years that it was produced. For the 2007 model year (starting 10/06 production), an auxiliary input was added to the BMW Business audio head unit, the previous Flat Tire Monitor (FTM) was replaced with a more accurate Tire Pressure Monitor (TPM) system, High-Definition radio became a factory option and Monaco Blue metallic (A35) paint was added to the exterior color selection list in North America (it was offered from the start of M Roadster production in other markets). For the final 2008 model year (which began in October of 2007), Silver Grey metallic (A08) paint was replaced by Space Grey metallic (A52) paint.
Drivetrain
What makes the S54 engine unique?
The S54 engine that powers the E85 M Roadster is carried over from the E46 M3 and is the final evolution of the iron-block S50 inline-6 that was first introduced in European-spec versions of the E36 M3 back in 1992. Though derived from the 3.2-liter S50 B32 unit used in later European-spec E36 M3s, the S54 features the following enhancements:
-Increased cylinder bore to 87mm (from 86.1mm) for a new total displacement of 3,246cc
-Modified camshafts
-High pressure Double VANOS continuously variable valve timing system with faster operation at high rpm
-Increased compression to 11.5:1 (from 11.3:1)
-Advanced BMW/Siemens MSS 54 engine management control
-Electronic throttle activation with two M Dynamic Driving Control response modes
-Finger-type rocker arms for reduced reciprocating mass and friction
-One-piece aluminum head casting for lighter weight
-Scavenging oil pump to maintain pressure during heavy cornering

The ECE-spec E85 M Roadster is rated at 343 hp (DIN) at 7,900 rpm and 269 lb/ft of torque at 4,900 rpm, while the North American-spec version is rated at 330 hp (SAE) and 262 lb/ft of torque at 4,900 rpm.
What type of transmission is used in the E85 M Roadster?
All E85 M Roadsters are equipped with a ZF Type H 6-speed manual gearbox featuring the following ratios: 4.35 (1), 2.50 (2), 1.66 (3), 1.23 (4), 1.00 (5), 0.85 (6). This is mated to a 3.62:1 final drive with M Variable Differential Lock.
What kind electronic stability control is the E85 M Roadster equipped with?
The E85 M Roadster is equipped with Dynamic Stability Control Plus (DSC+), an evolution of the earlier DSC system that retains Dynamic Traction Control (DTC), Dynamic Brake Control (DBC), and cornering stabilization (all of which can be defeated via a dashboard switch), but adds the following permanent features: brake fade compensation (increases booster pressure to adjust for rising brake temperatures), brake standby (readies the brake system for sudden braking when there is sharp lift off the accelerator), brake drying (activates based on data from the rain sensor and monetarily brings the brake pads close to the rotors in order to remove any water) and start-off assistant (applies the brakes for a few moments when the driver first releases the brake pedal in order to prevent roll-back).
What is the M Differential Lock and how does it work?
The M Differential Lock, fitted as standard equipment to every E85 M Roadster, is an advanced version of the traditional limited slip differnetial. Though still entirely mechanical in operation, the M Differential Lock is activated when there is a difference in rotational speed between the two rear wheels. This difference pressurizes a viscous silicon fluid, which then operates a multi-disc clutch that directs more power to the wheel with the greatest traction.
How does the North American-spec E85 M Roadster differ mechanically from the European-spec version?
Only a very slight variance in the placement of the exhaust catalysts differentiates the North American-spec M Roadster mechanically from the Euro-spec versions. This, along with a minor difference in how horsepower is calculated under the DIN (European) and SAE (North American) ratings systems, accounts for the 13-hp discrepancy between the two versions.
Chassis
How does the suspension of the E85 M Roadster differ from that of the regular Z4 roadster?
The E85 M Roadster utilizes the same basic MacPherson strut/multi-link suspension design as the standard E85/E86 Z4 range. However, it has been substantially modified by BMW M GmbH with the following changes:
-wider front track (by half an inch)
-revised lower aluminum front control arms with a design similar to that of the E46 M3
-steering knuckles bolted directly to the front struts
-larger and stronger rear subframe designed to accommodate the M Differential Lock
-modified longitudinal links in the rear suspension
-modified wheel bearings
-specific spring and shock rates
-thicker front (27 mm) and rear (21.5 mm) anti-roll bars
What type of steering system does the E85 M Roadster have?
The E85 M Roadster shares the majority of its rack-and-pinion steering system with that of the E46 M3. It therefore utilizes a hydraulically-assisted rack with an overall ratio of 15.4:1. (By contrast, the regular Z4 models are equipped with an electrically-assisted rack with an overall ratio of 14.2:1.) However, the characteristics of the power steering pump have been modified relative to the one used in the E46 M3.
What type of braking system does the E85 M Roadster have?
The braking system of the E85 M Roadster, which is identical to that of the E46 M3 CSL and E46 M3 with Competition Package (ZCP), consists of 13.7-inch cross-drilled rotors in the front and 12.9-inch cross-drilled rotors in the rear. These rotors employ a two-piece "compound" design whereby the aluminum hat is connected to the outer portion of the rotor via steel pins, which greatly improves heat dissipation under heavy braking conditions.
What are the factory wheel and tire sizes for the E85 M Roadster?
The E85 M Roadster is equipped with unique M Double Spoke alloy wheels (Style 224) in 8x18-inch (front) and 9x18-inch (rear) sizes. These carry non-run-flat tires sized 225/45ZR18 (front) and 255/40ZR18 (rear).
How does the chassis of the E85 M Roadster differ from that of the E86 M Coupe?
Though the vast majority of chassis components are shared between the E85 M Roadster and the E86 M Coupe, the following items do differ: steering ratio (15.4:1 in the M Roadster versus 14.5:1 in the M Coupe), rear anti-roll bar thickness (21.5 mm in the M Roadster versus 22.5 mm in the M Coupe) and shock rates (slightly softer in the M Roadster than in the M Coupe).


Cosmetics
How does the exterior of the E85 M Roadster differ from that of the regular E85 Z4 roadsters?
The exterior of the E85 M Roadster shares the majority of its body panels with other E85 Z4 roadsters. However, its more agressive front fascia features black "kidney" grilles that are inset further into the bodywork, as well as a more aggressive front bumper and lower front airdam. The unique rear bumper incorporates a lower diffuser and the quad exhaust tips that have now become a trademark of BMW M automobiles. Further exterior differentiators include twin "precisions lines" in the hood and the unique M Double Spoke alloy wheels, as well as, "M" badges on both front fenders behind the BMW roundel/marker light and a third "M" badge on the trunk lid.
How does the interior of the E85 M Roadster differ from that of the regular E85 Z4 roadsters?
The interior of the E85 M Roadster shares its basic design and construction with that of other Z4 models. However, it contains the following special features:
-M sport seats in exclusive Nappa leather
-Optional extended leather (in limited colors) with additional leather on the center console, upper door panels, windshield frame, sun visors and roll-over bars
-M leather steering wheel with a thicker rim and tri-color stitching
-M instrumentation featuring unique graphics, red needles, a 180 mph/300 kph speedometer with the M logo, a variable LED tachometer redline and an oil temperature gauge in place of the usual coolant temperature dial
-leather M shift knob with an illuminated gear shift pattern
-door sill plates with the "M" logo
-available Carbon Leather and Walnut Madeira wood interior trims
What were the available factory options for the E85 M Roadster?
Because all M Roadsters were equipped with a high level of standard equipment, there were relatively few options. However, the following items were generally offered at extra cost, depending on the market and production date: Park Distance Control, cruise control, power-folding exterior mirrors, auto-dimming interior mirror, power front seats with driver-side memory, heated front seats, Bluetooth phone interface, navigation system (Business and Professional), plus various audio and speaker systems including Professional Logic7.
Special Versions
NO OFFICIAL SPECIAL VERSIONS OF THE E85 M ROADSTER WERE PRODUCED.
Color and Upholstery Selections


The following chart lists all regularly available paint colors for the E85 M Roadster in all worldwide markets. NOTE: BMW Individual paints not offered in some markets.
PAINT NAME CODE GROUPPRODUCTION PERIOD
Alpine White III 300 BMW AG01/2006 through 08/2008
Imola Red II 405 BMW M01/2006 through 08/2008
Titanium Silver metallic 354 BMW AG01/2006 through 08/2008
Silver Grey metallic A08 BMW AG01/2006 through 09/2007
Space Grey metallic A52 BMW AG10/2007 through 08/2008
Black Sapphire metallic 475 BMW AG01/2006 through 08/2008
Interlagos Blue metallic A30 BMW M01/2006 through 08/2008
Monaco Blue metallic A35 BMW AG01/2006 through 08/2008
Sepang Bronze metallic A32 BMW M01/2006 through 08/2008
Carbon Black metallic 416 BMW M (special request)06/2006 through 08/2008
Phoenix Yellow metallic 445 BMW M (special request)06/2006 through 08/2007
Midnight Blue metallic 453 BMW INDIVIDUAL06/2006 through 08/2008
Ruby Black metallic S23 BMW INDIVIDUAL06/2006 through 08/2008


The following chart lists all regularly available upholstery colors for the E85 M Roadster in all worldwide markets. NOTE: BMW Individual upholsteries not offered in some markets.
UPHOLSTERY NAME CODE GROUPPRODUCTION PERIOD
Black Nappa leather LSSW BMW M01/2006 through 08/2008
Black extended Nappa leather LTSW BMW M01/2006 through 08/2008
Light Sepang Bronze Nappa leather LSA8 BMW M01/2006 through 08/2008
Light Sepang Bronze extended Nappa leather LTA8 BMW M01/2006 through 08/2008
Dark Sepang Brown Nappa leather LSD6 BMW M01/2006 through 08/2008
Imola Red Nappa leather LSIM BMW M01/2006 through 08/2008
Champagne Nappa leather LPCM BMW INDIVIDUAL06/2006 through 08/2008
Champagne extended Nappa leather LLCM BMW INDIVIDUAL06/2006 through 08/2008
Caramel Nappa leather LPCR BMW INDIVIDUAL06/2006 through 08/2008
Caramel extended Nappa leather LLCR BMW INDIVIDUAL06/2006 through 08/2008
Amarone Nappa leather LPF2 BMW INDIVIDUAL06/2006 through 08/2008
Amarone extended Nappa leather LLF2 BMW INDIVIDUAL06/2006 through 08/2008
Syrah Blue Nappa leather LPF3 BMW INDIVIDUAL06/2006 through 08/2008
Syrah Blue extended Nappa leather LLF3 BMW INDIVIDUAL06/2006 through 08/2008
Estoril Blue + Anthracite New England leather NBC3 BMW INDIVIDUAL06/2006 through 08/2008
Phoenix Yellow + Anthracite New England leather NBC4 BMW INDIVIDUAL06/2006 through 08/2008
Silverstone + Anthracite New England leather NBC5 BMW INDIVIDUAL06/2006 through 08/2008
Imola Red + Anthracite New England leather NBC9 BMW INDIVIDUAL06/2006 through 08/2008


The following chart lists all regularly available interior trims for the E85 M Roadster in all worldwide markets. NOTE: BMW Individual interior trims not offered in some markets.
INTERIOR TRIM TYPE CODE GROUPPRODUCTION PERIOD
Brushed Aluminum 4AD BMW M01/2006 through 08/2008
Carbon Leather 4MY BMW M01/2006 through 08/2008
Madeira Walnut wood 4ME BMW M01/2006 through 08/2008
Piano Black 4ML BMW INDIVIDUAL06/2006 through 08/2008


top