watch shows my max hr is 177. Try as I might, can only get it to 160. How to I get my watch to recalculate

You can enter the max hr manually, if you have a better value.

Oh yes, I know I can do that.  Just wondering if there is a way to encourage my watch to calculate a more reasonable max hr.  Am wondering if I should set my percieved effort at max when I do acheive max hr to let it know that was my max effort