Early production pulleys were both 70mm.
Read through this thread for more info:
https://www.bimmerpost.com/forums/sh...php?p=27883249
Edit: maybe I’m wrong.
From FCP euro:
https://www.fcpeuro.com/blog/how-to-...sioner-pulleys
“BMW E90 M3 Belt Tensioner Assembly & Replacement Pulleys
Power steering and A/C compressor tensioner pulley - p/n 11287838196 (
Up to 5/15/2008) - Use INA 5320557100 (OE# 059903341G) - 65mm x 26mm
Power steering and A/C compressor tensioner pulley - p/n 11287838194 (From 5/15/2008) - Use INA 5320342100 (OE #11281440237) - 70mm x 26mm
Alternator and water pump tensioner pulley - p/n 11287841527 (Used on all E9X M3's) - Use INA 5320342100 (OE #11281440237) - 70mm x 26mm”