These are routes that I have cycled and have enjoyed. Sorry, for the bias of the near-KL routes, its a reflection of my own wanderings and not an indication that the rest of the Peninsular is un-cycle-friendly. If there are any other cyclist willing to contribute cycle-friendly routes do email me at email@example.com.
Look up Malaysian Bike Friendly Routes
There have also been some interesting accounts of travels around Malaysia by bike, some of the more memorable ones include Monsoon Madness (a 800 km trip starting from KL) or the ever popular, Mr Pumpy's ride down the East Coast of Peninsular Malaysia. Also read up on the seemingly-epic journey of Jan Boonstra from Bangkok to Singapore. Yet another account worth reading is a tandem ride from KL to Mersing. For a fuller list of cycle-journals, check them out here in our Cycling Directory.
I have not been much of an off-road cyclist, but in researching this article, I have come across a number of inspiring webpages. One website which I have been learn a lot from and one that stands out over the rest, in content and in some very very impressive photography...the KL Bike Hash site. You'll find a wide range of guides to the "singletracks" of Malaysia. This is probably the most comprehensive collection of singletrack trails in Malaysia that I know of. Other links worth checking out are listed here. I have since bought a MTB of my own, and there are really some nice trails out there to explore!
Look up Malaysian Offroad Trails
Its not big in Malaysia. I have only found one or two companies that offer cycling trips (these are listed in our Cycling Directory), but they are not specialised groups. There is one international company Worldwide Escapes that runs interesting tag-on offroad tours outside KL.
As a rule of thumb, all the bike shops listed in our Cycling Directory are run by cyclists, and as such, they are also the foci for bike groupies! There are others, and these are growing with the rise of interest in off-road riding. To catch the full list, visit our Cycling Directory. There is also a local MTB forum maintained by the KL Bike Hash, its a source of useful information and discussions on riding in Malaysia, Bike Forum.
There aren't many pro-bike shops around, or at least bike shops you'd trust with your cycles. Those that I have listed in our Cycling Directory are some of the best around. Again, they are very KL-centric, so if there are any others you'd recommend, email me at firstname.lastname@example.org.
There are a few local sources around on the net to look for second-hand gear or to flog bike-related bits and pieces. Try: KL Hash Bike Forum; Singapore-based Togoparts.com; or KSH.