text: i want too buy a specialized rockhopper mountain bike with a 17 inch frame.  my height is 5"8". will it work?   the easiest and most effective way to judge the fit of a mountain bike it by checking "stand-over clearance", which is the amount of space between your crotch and the top tube of the bike when you stand over it.  generally speaking, stand-over clearance should be between 1" and 3" on a mountain bike.  how to test: 1) stand over the top tube of the bike with your legs shoulder width apart 2) now, lift the bike (front and back) until your crotch is resting on the top tube.  you can do this by grabbing hold of the top tube with one hand in front of your body and the other in back. 3) finally, check stand-over clearance by looking at the space between your tires and the ground (you are still lifting the bike, right?).  again, this should be between 1" to 3" for a mountain bike.    this assumes you have the bike in-hand and physically with you to perform this test.  in case you are purchasing something online, for example, have a look at what the folks at active.com say...  http://www.active.com/story.cfm?story_id=10184&sidebar=32&category=mtnbiking