August 2021 will see the arrival of the new M xDrive-equipped M3 and M4 Competition models, for the first time ever. The additional traction will enable the full 479 lb.-ft. of torque to be used to a greater extent during both acceleration and dynamic driving.
The fully-variable, rear-biased system distributes torque between the front and rear axles via an electronically controlled multi-plate clutch. An Active M differential takes care of torque distribution at the rear axle. Torque is directed to the rear wheels during normal driving, providing the classic rear-wheel drive experience. Only when additional traction is required, is torque sent to the front axle.
Both the M xDrive and Active M differential are connected directly to the Dynamic Stability Control System ensuring quicker responses in improving agility and controlling both understeer and oversteer. The transfer case also features a unique control unit and integrated traction control. This enables it to compensate for any differences in rotational speed between the front and rear wheels quickly, without having to involve the central DSC computer. This results in enhanced all-wheel-drive performance in highly dynamic driving situations, such as powering through corners in a controlled drift.
The M xDrive system also offers a choice of three drive modes: 4WD – the default setting with rear-wheel biased torque distribution focused on traction and precisely controlled handling. 4WD Sport – directs greater percentage of torque to the rear during dynamic driving and is designed to work particularly well on track environments. 2WD – requires DCS to be turned off and affords experienced drivers a pure rear-wheel drive experience without any system intervention.
The improvements in traction, handling stability and agility delivered by the combination of M xDrive and Active M Differential also translate into improved acceleration. The BMW M3 Competition xDrive Sedan and BMW M4 Competition xDrive Coupé both need just 3.4 seconds to reach 60 mph from a standstill, making them 0.4 seconds quicker here than their rear-wheel-drive counterparts. Depending on the specification, the top speed is 155 mph or 180 mph.
The Competition xDrive models are equipped with forged M light-alloy 19-inch front and 20-inch rear wheels shod with 275/35ZR19 and 285/30ZR20 non-runflat performance tires. The redesigned front axle geometry and a retuned steering ratio – from 15.0:1 to 14.6:1 – ensure that the all-wheel drive variants deliver the agility that the BMW M driver expects. The oil system has been adapted to handle the increased traction and performance.