52 miles is almost a metric century. Tell us a little about your goal route. Is it hilly? Expect headwinds? Besides the distance how hard is it?

You'll probably need to average 13-15 mph or higher to finish ahead of the sweep wagon. Or slow and steady and be incredibly efficient in and out of rest stops.

Sounds like you're doing fine right now. What do you feel stops you from longer rides now? Any pains, discomfort? Work to resolve those issues.