I also get cramps if I eat right before running (or swimming) but it is different with cycling. If I eat too much though, I do get a heavy feeling in my stomach.

I usually eat a mini bagel with peanut butter before my rides. Or oatmeal. Any ride less than 30 miles, and I usually don't eat. Unless I feel I need something, then I will have a Cliff shot block, or a Gu gel. For 50 miles or more, I like to have something more substantial, like a Cliff chocolate chip bar.

But yes, it really is all about trial and error. I remember taking a Gu halfway through my shorter rides, and now I feel I don't even need it.