for a group ride? idk... depends on who I'm with and how I feel at the moment. you'll know it's too fast IMO when I don't follow you.
for me usually the highspeed shit is out away from everything... on the freeway or some long straight on a back road out in the sticks.
I will say if there's a cross street or a chance someone can pull out with out me seeing them... I stay under 100(or try to

)...