I've just started using a HRM also. I've hit a max of 175 but only once. The first few rides I tried not to focus on the hrm but ride at a PE similiar to that of which I was accustomed. I've noticed that I tend to be in the low to mid 140's without fail. I'm trying to correlate a PE to HR. It's all new to me though so much learning to do. I've been told that your recovery rate is a good indicator of your fitness also.

Yesterday I did a 25 mile ride/loop. First half into a pretty stiff wind then back. I can tell you at simililar HR's I was going almost twice as fast on the way home as out. Great ride.