The size of spacer will depend on the offset of the wheels you use. If they are OEM wheels, 15mm will be fine. And IMHO aggravated bearing wear would only occur if you used some really wide spacers (30mm+).
E92 pre-LCI 325i
- Ohlins R&T; H&R spacers; BMS clutch stop; BMS CDV; RE g/box mounts; Saikoumichi OCC; K&N; Cyba scoops; BMW Perf Exhaust; M3 rear spoiler; LED Angels; BMW Perf black grille; SSDD carbon diffuser; Monster Wrap black roof