Munich boasts a superb network of cycle paths, which locals use to commute to work.
Cycle hire is easy to arrange. Try Radius Tours at the Hauptbahnhof.
Bikes can be taken on the S-Bahn but not from 6am to 9am and 4pm to 6pm Monday to Friday (rush hour). All bikes need a ticket.
Helmets are not...
Driving in central Munich can be a nightmare; many streets are one-way or pedestrian only, ticket enforcement is Orwellian and parking is a nightmare. Car parks (indicated on the tourist-office map) charge about €1.70 to €2.20 per hour.