Among the expected 5,500 cyclists riding in the second day of the Pan-Massachusetts Challenge on Sunday will be 56 riders from Medfield, and it’s not too late to support them, organizers said. Go to www.pmc.org, or call 1-800-WE-CYCLE and give them the name or registration number of the cyclist you want to support. In the Pan-Mass Challenge, bicyclists choose from 11 routes of varying distances; there are six two-day routes that range from 153 to 190 miles, and five one-day rides that range from 25 to 110 miles. For this year’s event, cyclists are required to raise between $500 and $4,300; their efforts are projected to raise $36 million to support research and treatment of adult and pediatric cancers at the Dana-Farber Cancer Institute through the Jimmy Fund. The PMC event includes food and water stops, mechanical and medical assistance, luggage transportation, and lodging stops for overnight treks along the routes that wind through 46 towns across Massachusetts.