If your previous long ride was 52 miles and that was painful you are really gonna hurt if you don't do more mileage. I do pretty well upping my longest ride 20 miles per week. If you get to 80 miles the week before the century you will find it much more enjoyable. Your rear end, back, neck, arms, legs all need time in the saddle to adjust and build up. I was amazed when 90 miles became comfortable.