I know that I cannot eat heavy items like Clif Bars during a ride. They just lay in my stomach and I don't think we can convert those carbs to something useable by our muscles easily. I use Clif Shot Blocks, which are lightweight and I seem to get energy from them faster. There are other carb replacements that are more digestible than the bars you have been using. On longer rides, I drink a Cytomax mixture with my water. Again, it's the idea of getting the carbs in a more digestible form so that your body can use them faster.