I bought a bike near the beginning of November to commute back and forth to work (just over 2 miles each way) but I also want to use it for general health and recreation.

When I first started riding back and forth to work I'd average ~12-13mph (guesstimate).. if I was on the road and tried to go fast (17mph+) I wore out very quickly.

Although I live in Hawaii where the weather is good mostly year round I bought a cycleops fluid trainer about a week or so ago since I live in the city and haven't gotten completely comfortable riding in traffic (even though I do stay on the road when I ride now). At the same time I also bought a cateye computer that measures cadence and speed via back tire.

When I first started on the trainer it was tough to go 4 miles averaging 13mph (computer) and a cadence of 60. Tonight I set a personal record of 10 miles on the trainer with an avg speed of 14.5 and avg cadence of 70 - which I maintained most of the ride.

I keep seeing people talking about how they average a 90 cadence and 18-19mph. While I can get 21-23 mph for short bursts in a high gear while mashing it, even in lower gears a 90 cadence is absolutely KILLER to me (speed about 15mph at that cadence in a gear i can do it). I can't maintain a 90 cadence for even a minute in a gear that will keep me above 10mph.

I don't really know what my question is.. For now should I just keep riding at a mph that keeps my heart pounding and sweating profusely whatever the cadence is? should I stay in lower gears and try to get where I can maintain a 90 cadence even though pedal effort has to be really low for me to spin that fast?

The trainer does seem harder than the road as I can maintain 19-20 mph on the road at a 60 cadence for a 1/4 mile or more - I can't do that on the trainer.