roadie,

ausgirl is correct in that heart rate numbers only matter inso far as determining your training zones and working with your numbers to get where you want to be. When you hit 180, you could be close to your max. It is difficult to stay close to your max for very long and that's probably why you are getting dropped. It sounds like a matter of more training. You won't up your MHR but be able to ride closer to it for a longer time. Also, as you get stronger you may find that you can pick up the pace without your heart rate going so high. I am NOT any sort of an expert on this. Maybe someone else could you give you some ideas on how to train to achieve what you want. Otherwise, there's lots of books out there. Check out www.roadbikerider.com. It is a wonderful site. Lots of info and also books that are available for purchase. Good luck. Keep working at it and you'll only improve.

annie