So i have been back into riding for about 4 months now and am getting back to my previous best performance levels and even surpassing the previous levels in Road riding. When i am on the mountain bikes i never have issues with cramps or soreness. But the last 2 Road rides i have went on (20.1 miles each, avg. 18mph-ish) Toward the end of the ride which about 8 miles of that is bridge attacks over the river 10 times. I get really bad calf cramps. Bad to the point of i need to get off the bike in a hurry! I ride 10-15 miles in the trails and have no issues what so ever. I eat at least 3 hours before the ride and have a fruit and nut bar at the start of the ride. During the ride i have a diluted G2 Gatorade and water mix and another water. What should i try differently? What am i doing wrong? Why is this not happening on the Mountain bikes?