I am not 50 i am 48 years old i hope is okay i write here. Today i do 20 miles in hilly trail. No have ride for almost 4 years.i be bussy. i not sastify with my ride i have to walk for some feet 3 times. Maybe i use wrong size crank and cassete for that trail. i have 53/39 crank and 12-25 9 speeds cassete. my bike is steel and weight around 25 pounds. What bikes do you ride and what size crank and cassete you use