Bicycle Mechanics - what bike size?

Hi.... How do I find out my bike size?
I have one now but no idea what size it is. And I'm looking at getting a new one... I see inches and centimeters...
I'm about 5'5". What is a good size for me?

Bike size depends o leg length vs. upper body length, the type of bike ( a 53cm bike from one company is not the same as a 53 cm from another company), type of bike (mtn, road, touring, etc), riding position desired and a host of other things.

Get thee to a good local bike shop and have them do a "fit" for your. No way anyone can tell you here. There is also a good article on fit of a bike at:

www.sheldonbrown.com

DF's advice is spot-on, but I can give you a VERY rough guideline to get you started. I am 5'8" tall and wear trousers with a 30" inseam, and my two 55cm (C-T) road bikes, both of which have longish top tubes, fit me beautifully. 52cm C-T would not be a bad place to start your search.

thanks guys for the input. i'll check out that site too.

There are fit guidelines at www.coloradocyclist.com as well as www.wrenchscience.com and www.anvilbikes.com. also seee www.rivendellbicycles.com for a different slant. They are not absolute, but will get you started and serve as a self defense against LBS morons trying to sell you something tht is not even close.

Some bikes are designed to have more clearance over the top-tube than others. MTBs are designed for about 3 to 5" clearance, larger on some models.
Standard road bikes are designed for 1" to 2".
Compact frame road bikes are designed for 3" to 5"

Bottom brackets vary in their height from the ground, so 2 frames of identical "size" may vary in their standover clearance.

Frames of different manufacturers sometimes vary in their height/length.

Modern road frames often come with very low top tubes to permit very low handlebars. This is only valuable if you are a competative time trialler. For normal riding , a higher bar position is more comfortable.

Take a trip to a good bike shop and try out some bikes for fit. maybe rent a bike for a weekend to see what size you like.

By the way, I think your first question has gone as yet unanswered.

You measure the size of a bike by its seat tube length. Typically this means from the center of the bottom bracket up to the top of the seat tube or to the point where center of the top tube intersects the seat tube. And the numbers you see (55, 53) are centimeters.

Cheers,
Jamie

Do beware of bike shops which try to sell you what they have in stock, rather than what you need. (It happens!) Since various brands and various models will feature different top tube lengths for a given frame "size" (seat tube length), buy what fits YOU.