Probably too late to the party, but from my personal experience: I used to lift weights regularly and ride, my body fat at the time was between 10-12%. When I dropped from 180 to 170lbs (was going through a stressful patch and lost some muscles), I started "flying" up the hills. The difference was unbelievable - wherever I was struggling before became super easy.
My biggest problem at the time was balancing between maintaining/gaining muscle mass while logging longer miles on a bike.