Tightening emissions regulations have forced BMW to change the propshaft material for its M3 and M4 models.
The M3/M4 propshaft is currently made from carbonfibre, one of a number of carbon components that help keep kerb weight to just 1497kg for a manual M4. In comparison a Mercedes-AMG C63 S Coupe weighs 1725kg, though a fairer comparison is a DCT-equipped M4 which is 1537kg.
Future emissions regulations have required BMW fit a new petrol particulate filter which leaves insufficient space for the current-diameter propshaft.
Rather than develop a smaller-diameter carbon propshaft for the rest of the M3/M4’s current lifecycle (expected only to run until 2019), M Division has developed an M-car specific steel propshaft which will be fitted to all M3 Sedan, M4 Coupe and M4 Convertible models from November 2017 production onwards.
The forthcoming M4 CS will retain a carbon propshaft as its higher 600Nm torque figure requires the thicker-diameter propshaft and its production run is expected to be completed prior to the new regulations coming into effect.
BMW says “the newly developed steel driveshaft has been designed to ensure the superlative performance and handling qualities of the BMW M3/M4 remain unaffected”, however there is no word on if there is a weight increase associated with the new material.
Total deliveries of the current-generation M3 and M4 have now topped 68,000 and Australian sales are likely to score a boost towards the end of 2017 with the arrival of the exclusive CS and cut-price M3 and M4 Pure models.