We visited Thetford site last week for four days. We always take our bikes as we prefer to cycle using an OS map and finding small roads and villages etc. However, we found it very difficult to access anywhere without cycling on the main A road which was just so busy. Some of the trails through the forest are quite deep shale so unless you have wide tyres its very tricky riding. We did manage to find our way round to Ickburgh and then Lynford Arboretum and Lynford Stag but by cycling through the forest trails which although enjoyable, are very bumpy. So although it is a beautiful peaceful site, you can't get very far on your bikes unless you're happy to go on the A roads.