Training & Nutrition - Cadence, Speed and Comfort

I am a relatively new rider who is just starting to get back into this. I bought a bike computer that has cadence. I rode a 33 mile ride the other day on relatively flat with a 2% grade here and there (The Silver Comet Trail near Atlanta, Georgia). On the ride I noticed that my best pace seems to be 70 to 80 rpm. I can go faster then that. In fact I had it up to 100 a few times. Bu it seemed that I could ride for long distances at that pace with little or no problem. In the gears that I was normally in this resulted in something like 15-18 miles an hour. I am riding for exercise and maybe a little light touring so I do not plan on being a speed demon or racer. But my question is this. Is something wrong with me? Should I be shooting for a 90 cadence like I keep on hearing about on this forum? Should I get a heart rate monitor to show that my cadence is enough or not enough? My average on this trip was only 12 miles per hour but there was a lot of areas where there was too much traffic to travel much faster then the walking groups.

if you're going for fitness, theoretically, a higher cadence should give you a better cardio workout and make you a more efficient rider, allowing you to go for a longer distance. it takes a few rides to get used to, but 90 is defidently a good target

It seems to me like your cadence evolves naturally. When I started, I would mash bigger gears and I never once made it my intention to go with a higher cadence. I had never really noticed that my spin had become any faster, until one time, on a group ride, a guy who had been riding behind me for a long time commented on how fast and smooth my spin was. I wasn't sure if he was just smoking carck or what, but I started measuring my cadence by counting (I don't have a comp. with cadence, but it does have a stopwatch) fifteen seconds and multiplying by four, and I realized that it was consistently between 95 and 110 without even trying to spin fast. I realized after that that I could spin at around 130 before I started to notice any cadence bounce. Hmmmmm... pretty cool.
I wouldn't worry about it too much. As you start going longer, I believe that you will naturally progress towards a higher cadence. Just do what feels comfortable for the time being.

by the way, if you ride with clip ins and start working on a circular pedal stroke, you will naturally spin faster. this is when you not only push down on part of your stroke, but pull up on the other. this is a more advanced technique, but i know some people who have really struggled to achieve a higher cadence until they started working on this. like bpohl said, for the most part, it comes naturally as you ride more, but Just something to think about

I agree with Bpohl. It just sort of comes. You can help it along by tyring to spin a little faster, just a rpm or 2 each week. I hit the gym last week to start winter training (yucch!), and the exercycle has cadence, of course, MY bike doesn't, and I think of myself as a masher. So I am dialing up the resistance, and not paying much attention, but enjoying the experience and I look down I am cranking over 130 rpm. Where did that come from? Beats me...