Where can I learn more about bikes? Can you enlighten me as to the difference between a $900 bik versus a $1500 bike?

Bicycling Magazine.

Bicycle Guide Magazine.

The big differences are in light weight, stiffness, and ruggedness.

WEIGHT: A good place to start is light weight. I have always maintained that it is so difficult and so expensive to make a bicycle really light weight that the manufacturer will have already taken care of the basics on the way to making it light. There is no percentage in hanging $1200 of components (or $4,000 for that matter!) on a poorly-made heavy frame. Conversely, it makes little sense to spend a lot of time and money building a really good frame and then hang low-end components on it.

Another thing to consider is riding habits. You can look at a top of the line Shimano XTR component set that sells for perhaps $400 more than a lower level XT set, and yes, it will be lighter, but not a [lot] lighter. You're probably looking at a 23 pound XTR mountain bike vs a 24 pound XT mountain bike. And initially, the XT components (shifters, brakes, pedals, derailleurs, hubs, freewheel, headset, bottom bracket, chainrings) will work exactly as well as the XTR. But, ride in competitive conditions with so much mud caked on the freewheel that you can't even see the cogs and the derailleur - and the XTR will keep going when the XT might fail.

I am a competitive cyclist. Actually, I need to re-phrase that: I enter bicycle races, but am hardly competitive at it. I have raced in two national championship road races (DNF one of them with a flat tire; finished in the top 90% in the second one*) but I do not consider myself to be a caliber of rider that would need XTR components. XT is perfectly adequate for my purposes even though most people would say I was a pretty serious cyclist.

STIFFNESS The lighter you make something, the less stiff it becomes. This can only be overcome with the infusion of significant amounts of money. Surprisingly, there is no magic wand you can wave to solve this, like building everything out of .04-Gage Unobtanium or something. Aluminum is lighter than steel, everybody knows that. But... the weight of an aluminum tube that will resist X amount of bending force is astonishingly similar to the weight of a steel (or titanium or magnesium) tube capable or resisting the same forces. Composites like carbon fiber are not the answer, either. While they are enormously strong in tension, they are less than satisfactory in compression, and virtually all of the stress loads in a bicycle frame are compression.

RUGGEDNESS It is easy and cheap to make a bike rugged. Just go down to your local department store, and lift the kids bikes for sale there. These are bikes designed to take all the punishment a 10 year old can dish out -- and many of them will weigh in excess of 40 pounds. Anybody can make a bike that will stand up to all sorts of abuse if they don't mind adding an extra 15-20 pounds to it. But to make it light weight, stiff, and rugged all at the same time... well, that's where the difference between a $900 bike and a $1500 bike comes in.

And why would anybody care if it has all three of those attributes?

I can only speak personally to that question. YMMV, depending on whether you bike for transportation or for enjoyment. Surprising as it might seem, I work much harder on a top quality road bike than I do on a cheap bike. A cheap bike, I sit on the seat, push the pedals around, and the bike goes forward. Blah. Little reward for the effort given. A high-end bike is different -- I step on the pedal, and the bike jumps. It is so lively and so responsive to my every input, that I want more of that feeling. I give more to get more. And before I know it, my heart rate is at anaerobic threshold, I am down on the drops, the legs hurt but they hurt so gooooddd... and incidentally, I am also going about 30-40% faster than I could go at the same workload on the lesser bike.

Mountain bike is same but different. There is something inherently satisfying about having a machine that just works and does everything I ask of it. Click the shifter, and it changes gear perfectly, every time. One finger on a brake lever gives enough power to lock either wheel on dry pavement. Stuck in a wheel-rut on a dirt trail? Good suspension and frame geometry means I just think about climbing out and the bike does it without drama. Rebound damping is perfect thanks to that $300 rear shock. 27 gears gives me the right gear for every speed from 1.5 mph to 45 mph, and I get to look on with amused tolerance at other people in the ride/race who are fighting chain suck, poor shifting, bad handling...

It's difficult to put hard numbers on bicycles (other than how much they weigh) because so much of the differences/advantages/disadvantages are intangible, but nonetheless real. To really understand the differences, you pretty much have to experience them in person -- not just a ride around the block, but for an hour or two. And don't even try to evaluate a mountain bike by riding it on pavement.

tanstaafl.

*"...top 90%." Think about it...