I wasn't sure. So if I took a picture of the different bikes in a model, in the same size, they will look exactly the same, and I can only tell them apart by the paint job, and perhaps a close look at the joins. Will the same model have the same basic frame material? I mean will they stick to steel, or aluminum. This would make a great difference in the ride, wouldn't it? Or does the geometry have different effects than the materials?

Also, what is the relation between different sizes?

Well, let me ask, what exactly IS geometry? Is it all a matter of angles? I can see that many angles can be the same for different sized frames. But some proportions have to change. If tire size stays the same, and the frame changes size, the changes cannot be proportional. And a smaller frame will be more rigid than a larger frame, because it has shorter members. So do manufacturers try to "fix" this, or do they just follow some rule, and if it makes a poor bike in some cases, they simply don't make that particular model in those sizes?

Don't worry about getting too technical on me. I have a BA in math. Or just a good link or two would be okay. I guess what I am really asking is if I read a reveiw by someone who is 5'0" and I am 5'8", how much can I rely on their reveiw? Do I need to factor in the difference in size of frame.

Or perhaps I just sit around and think too much, and just need to ride some bikes

Mary