When I started cycling more seriously I was 48. At the beginning my max HR from running was higher than cycling. During the first yr or two my max HR during cycling increased until it matched what I can get to running. It stayed constant for a number of years and I'm not sure what it is anymore. Max HR is not something I see on a weekly or monthly basis. It's usually a once a year kind of effort in the summer up some hill. I'm not motivated enough to test regularly