Quote Originally Posted by irrealised View Post
it's nice to know what the averages are of typical group rides
Club rides are normally "keyed" A,B,C and sometimes D. The club website or newsletter should explain the speed range for each group. That can vary from club to club, and it can also vary whether it means "this is how fast we sustain as a paceline on flat road without stop signs" or "this is our average speed over the whole ride."

If a club ride is so small and congenial that it isn't keyed, then IME it's usually mutually agreed on at the time of the ride by whoever shows up (which would include you if you showed up), and they might split into smaller groups or all agree to ride at more or less the slowest riders' pace.