A/C and Alternator Belt, 8PK1400 - F87 M2 S55, F80 M3, F82 M4
OEM replacement belt covers the air conditioning and alternator
The main drive belt runs the air conditioning compressor and alternator on the S55 engine in the F87 M2, F80 M3, and F82 M4. It's very important not to neglect your drive belts as a failure will leave you stranded. They're easy to inspect during normal maintenance such as an oil change or refilling your washer tank. If there are cracks running across the ribs, sections missing, the edges are frayed, or the threads are visible on the belt surface, the belt should be replaced immediately.
If you can, inspect and test the pulley and tensioner before ordering your belt. Or plan to order new pulleys and tensioner with your belt. These pulley is made of plastic and shatter with age, causing potentially expansive/expensive damage to your engine, radiator, etc. The pulley and tensioner are sold as one piece.
F87 (2016+) > M2 Competition S55 (2019+)
F80 (2015-2018) > M3 (2015-2018)
F82 / F83 (2015-2020) > M4 (2015-2020)