[jpravetz]

Unfortunately, for off road, even though the classification of whether bikes are allowed on a trail can be input, I haven't seen any viewers that show this information. I find it difficult to determine the trail type (single/double track), condition (dirt, pavement), and whether bikes are allowed.

[rmc]

OSM has classification schemes for tagging mountain bike routes http://wiki.openstreetmap.org/wiki/Mountainbike

This might be of interest to you http://openmtbmap.org/