Does anyone have any ideas what speed will be needed to be competitive at this event for the 40 year old range? It is only 17 miles and the event says that it is a fast course. Just looking for some numbers!!
It'll depend on wind conditions the day of the event, but for a reasonably flat and non technical time trial like that at altitude in open category but age graded groups I'd expect the winner to average 27-29 mph for the 17.4 miles and everyone in the top 10 to average at least 26 mph for the 40 year old group.
If there's a big turnout you'll probably get average speeds down to 21-23 mph for folks further down in the standings but I'd be very surprised if the top riders in the 40+ age group didn't average at least 27 mph and probably more unless it's real windy on the day of the race.
If the turnout is good for this event you're going to have category 1/2/3 riders in this age range with full TT bikes and full aero kit that are really good at making a TT bike go fast. Top age graders at nationals regularly set times that work out to 28-29 mph for full 40 km time trials and Colorado has a lot of very fast racers.