A good place to start: http://www.fietsroute.org/indexuk.php
In general Flanders (the North of Belgium) is easier for biking, because of the flat landscape. Also, Brussel is NOT a bike friendly city. So if moving around by bike is important, maybe replace Brussel with Gent or Antwerpen in your planning. (Brugge is perfect as a base for bike trips.)
Brussels has several bike tours organised by the local bikers association. The website is in English but the scheduled tours are in French. If you book a private tour then you can have it in any of the six languages offered, including English. See details here:
The tourist attractions in the city are split between the upper and lower part of Brussels, which means that moving around with a bike is not easy due to steep streets and there is only one lift that connects both parts of town (near Place Sablon). Brussels have very nice bike paths and routes but away from the tourist attractions. In case you really want to explore the city, get a map for bikes that shows the difficult streets, red for the really difficult ones and pink for ones that are hard but not too much. You get them for three or four euros in any bike repair point, one in each main train station: see contact section of this website www.recyclo.org/en/locatie/bike-point-central
Ghent is a lovely place to visit by bike but as the tourist attractions are in a very compact area, I found myself leaving the bike in one place and just walking. Not worth renting a bike unless you want to explore parks or areas out of the beaten track.
Bruges is perhaps the best place to really go cycling. No need to bother with local websites with no English version, just go to the tourist info point and buy a map of the bike routes (includes English section), Flanders bike routes are well marked, there is no way to get lost.Edited: 5:45 am, August 09, 2014
-:- Message from TripAdvisor staff -:-
This topic has been closed to new posts due to inactivity. We hope you'll join the conversation by posting to an open topic or starting a new one.
To review the TripAdvisor Forums Posting Guidelines, please follow this link: http://www.tripadvisor.com/pages/forums_posting_guidelines.html
We remove posts that do not follow our posting guidelines, and we reserve the right to remove any post for any reason.