Max HR is really not the ideal way to set your training zones. This is partly because it's difficult (not to mention really painful) to accurately test, and partly because what matters more is your HR at lactate threshold (LT). If you want to reduce your HR at a given power output (i.e. speed) you need to improve the capacity of your aerobic energy system. There are a variety of effective training plans that can help you do that, but they require training in specific zones relative to your LT. Training Peaks has some well written articles on the subject:
Power Training Levels | TrainingPeaks