On Aug. 5-6, 48 riders from Winchester will cycle up to 192 miles in the Pan-Mass Challenge with the goal of raising $48 million for research and cancer care at Dana-Farber Cancer Institute.During PMC weekend, more than 6,200 cyclists from more than 40 states and eight countries will return to Massachusetts to participate in the PMC, choosing from 12 routes of varying mileage that run through 46 towns.