You can start with just a five or 10 minute ride and work up from there. For regular exercise, about four or five miles would be plenty, but depends on your dog and how fit he is and his energy level.
If you are on pavement a lot, one thing to really check for are his paws. When you start, stop often and check for bleeding, raw paw pads. You can start conditioning his paws now by walking him on pavement a lot before you start biking.
BH, OB1, TR1, AD
Rottweiler/Hairy Dog mix?? Shelter rescue
Gryffon Vom Wildhaus