My instinct would be to hit them harder, whole legs, not just hamstrings, i.e. heavier weights, slowly working up to weight which you would fail to move after the 5th rep. But be very careful of form for the hamstrings. Have a trainer help you with that. And do exercises in the same range of motion as on the bike. I've always found that heavier weight heals faster. "Gotta stimulate 'em."