My six month old Doberman gets very upset when I sit on or ride my bicycle. She will bite my leg as well as the tires on the bike. I have only tested this out for a couple minutes and then stopped once I realized how it was affecting her. It seems to be the same behavior that affected my other doberman when I was a kid. She used to like to chase bikes as well as tires on cars. Can anyone give me advice on this behavior and what to do to solve it. Thanks.