I used to bike with my 9lb rat terrier mix - she loved it. I just didn't go as fast because she had 3x the ground to cover as my GSD did - And conditioned her to longer runs/ watched her for signs of fatigue. Just common sense stuff.
Danielle, owner of...
Fraggle Rock Collars
Fraggle Vom Richcreek CGC CA
Sir; Rescued APBT
Red Dog's Reconnaissance Man CGC
General Patton Vom Winter Storm