It is perfectly feasible to take your bikes on the majority of German trains, we have used it several times. There are some exceptions such as the superfast ICE (Inter City Express) trains. With a bit of forward planning it is not too traumatic and we found that most of the information & ticket offices in the stations were quite helpful.
You will need to purchase a separate ticket for your cycle from the ticket office. Prices are not as cheap as in Britain but reasonable.
Most of the stations that we used had good access to the platforms for heavily laden touring cycles i.e. ramps & lifts etc. and there are special places reserved for cycles on the trains, these are clearly marked by cycle symbols on the doors.
BUT when it came to getting on the some of the local trains !!!! (see picture left).
As you can see from the picture there is a massive 3 steps up to the carriage from the platform!
This is very much hernia inducing and back wrenching stuff so unless you wish to do yourself a mischief think about unhooking those panniers before the train arrives, the DB recommends that you remove luggage from your cycles to conserve space inside the carriages anyway.
If you are really lucky and your train is a Intercity or a Regional Express train like the one that we traveled on from Frankfurt Oder to Hamburg, it was simplicity itself as the doors are at the same level as the platform and you could wheel them in fully loaded with no problem.
For more information on trains in Germany visit the Deutsche Bahn website.
Neil from Bergstrasse Bike Books sent me this info. on taking tandems on German trains
German trains take tandems, but they cost twice as much as a normal bike. If you are going to travel on an express train (IC or EC) then you should reserve a place on a train as soon as you know when you are going to travel. You cannot book these tickets online, try the German Railways hotline (details on www.bahn.co.uk) or book them in Germany at a manned railway station. The superfast ICEs do not take bikes apart from bagged folders. If you are prepared to travel a little more slowly you can travel on regional trains (RB, RE) where you don't have to reserve bike places but you probably have to pay and you can use Laender Tickets which may well cost less than 2 singles even with two people. There is some more info. on our web site.