Depending on how hilly the course is your training for if you can get to a point where your average speed is around 18mph you will be in great shape. Try this, go to www.pickleevents.com. On the top menu click on results and then for example click on the results for the Northwoods triathlon. That race had a hilly 15 mile course. Find your age group and you will see average bike time for the riders. Check the other races for longer bike events.