<< if cost is not a factor than get the best dual suspension, carbon fiber >>
eeeeeeewwwwwwww!!!!!!!!! Carbon fiber and suspension are the two worst things about mountain bikes.
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<< I'm ~5' 8" 5' 9" so I'm guessing the 21" is good? Is this bike good for long trips and high speeds? I'm not talking about speeds like on a racing bike but 25-35KM/h? I use my bike to go to work and get around town, will this bike bring me there easier then my CCM aluminum bike? The shipping weight is only 30lbs so my guess is that bike is light, my current ccm bike is about 35lbs. >>
No, no, no! A 21 is about right for me, at 6'4". No offense but if you are this far off-base on sizing this will NOT be a hot deal - size is the most critical issue in finding a bike you will enjoy. Even the 19" is probably too big, unless you NEVER intend to take it off-road. >>
I'm 5'9" and I've always ridden mtbs in the 18-19" range, even off-road quite a bit. It depends on how the frame is measured. Anyway, if you're a bike newbie, you should probably buy from a local shop. Most usually throw in a year or two of free maintainence, so that's something to consider. >>
I am 5'8" and I feel most comfortable on frames that are 14 to 16 inches.