I get cramps usually at about 60-80 miles into a century. I slow the pace and keep on pedaling. They usually lessen. I have tried many things and don't have a complete solution. I do better when I don't follow the faster riders in the first stretch. I had good luck with taking magnesium pills every day for the week before a ride. I have found that salt tablets taken just on the day of an event sometimes help but sometimes don't. I will try pickle juice. I have read a lot of articles on cramping and I believe conditioning is the biggest factor. I experienced almost no cramping about 4 years ago when I did 4000 miles starting in January and just kept it up!