I think riding with a group or in an organized ride makes you go faster. I just did the MS150 this past weekend. Prior to the ride, I usually averaged 14-14.5 mph on my training rides (~24-50 mile distance). On the Saturday leg of our ride, we averaged 16.5 mph - the fastest (and farthest) I have ever gone. I think all the excitement and adrenaline just kicked it into high gear. Our Sunday leg of the ride slowed down - 14.5 mph. Sunday started with hills from miles 8-16 or so and it got VERY hot - in the 90's. I think those factors along with the fact that we had just rode 75 miles the day before slowed us down. I still think 14.5 was pretty good all things considered.

All that said, I don't think it matters how fast you go. If you're on the bike - good for you! You're out there riding which is all that really matters. My co-workers like to ride at 18-22+ and I am totally ok bringing up the rear when I ride with them. My Dad rides at about 12.5 mph and sometimes I really enjoy a slower, less strenuous ride with him. Riding is riding and if you're having fun - more power to you!!