text: Try insert http://wiki.openstreetmap.org/wiki/Key:sac_scale 
  http://wiki.openstreetmap.org/wiki/Key:trail_visibility
  http://wiki.openstreetmap.org/wiki/Key:tracktype
  http://wiki.openstreetmap.org/wiki/Key:surface
  http://wiki.openstreetmap.org/wiki/Key:smoothness
  And of course http://wiki.openstreetmap.org/wiki/Key:incline if you know the values.