Max Hr is a funny thing. When I had it measured a few years ago in a clinical trial mine was 212, but...
That was the point at which my blood pressure suddenly dropped and my heart started to beat funny - not something that anyone should do on a bicycle (or a track or swiming pool for that matter), nor is it something that the average person can push themselves into. The actual test was a clinical evaluation of exertion and pain threshold tolerance for soldiers in battle.
I use a HRM, but I have never put a lot of faith in it. It is more a toy than anything else.