Originally Posted by
hobkirk
I expected a 1 mile flat-out interval to be a lot more than 3 mph faster than a 18 mile ride!
I think the answer is: "You have only been riding 2 1/2 months and concentrating entirely on long rides, not speed training. What do you expect? More distance rides will only raise your top speed slightly, you need to do a lot of speed training, like intervals." Right?
As others have stated, your HR max and zones are unique to you. What is important is how much power your body puts out at the threshold point. Establishing good pedal technique, just like running form, is critical for improvement and as the platform to work off of. Once you establish your HR zones you can divide your workouts into recovery, Z3 endurance building, higher intensity intervals consisting of longer Z4 intervals and shorter Z5 intervals for speed. Over time your speed, average MPH, while riding at the same effort will increase as your muscular endurance in the Z3 develops.
After a couple years of training I've discovered my personal max HR to be around 172 and have developed my zones around that number. Keep in mind that your max HR may change over time. At first the muscles used for cycling may quit before you hit your max HR since you are only using specific leg muscles which fail before you really hit MHR even though the body is saying it can't go any more.
Doing the 3 minute intervals you are doing will make a difference. Once again it takes time to get stronger. In order to ride faster on longer rides one need's to have form, endurance and speed. Doing high intensity intervals will develop speed. FWIW, two years ago when I did 6 x 1mile intervals with 10 min recovery between reps my average speed for the intervals was in the 24 mph range. Two weeks ago when I did 1 mile intervals the times for the 6 intervals ranged from 2:06 to 2:11 which was an average of around 28+ mph. I did a 10 mile, out and back, time trail earlier this summer using my road bike and averaged 24.05 mph.