Originally Posted by humbug
i'm 5'8" with about a 30" inseam, and i've heard people tell me i need everything from a 52" seat tube to a 55. this is confusing for me, especially since i am looking at the lower end bianchis, which all jump from 52" to 55" with nothing in between. so in everyone's experience, is it better to err on the size of smallness or bigness? what are the advantages/disadvantages of each? thanks in advice for your help.
Who's telling you what size you need?
Seat tube length was never a very good way to size bicycles. If you think of it, seat height is the easiest adjustment to make on a bicycle. Why would you use that measurement as the do-all end-all determining factor? Making it even more complicated are the relatively new compact frames that result in smaller seat tube measurements and make stand over estimates useless.
My advice is to shop for a shop first. You need to find a bike shop guy whose experienced in bike fitting. Once you find the right guy, everything else will fall into place.