Laura and I managed to squeeze in a mornings biking on Tuesday 26th October before heading into Edinburgh for lunch with my parents!
We headed to the Pentland Hill just south of Edinburgh and parked at the Harlaw Ranger Base car park and did a 18km loop south from here via Glencourse Reservoir. The Pentlands do not have that many tracks that are set up for mountain biking however they do offer a good half days exercise. If you want more info then pop into the Ranger Base and they will show you some good routes.
As a quick plug if you are local to Edinburgh and use the Pentland Hills then the 'Friends of the Pentlands' is a great organisation that help maintain and raise awareness for the Pentlands - http://www.pentlandfriends.plus.com/index.htm