measuring a road bike

bobbieocean

Hello!
I am a beginner road cyclist. I have a new to me Specialized Roubaix 27 from 2004, I was able to identify the model and year with the help of the folks at Specialized. They are very helpful. Anyway, the missing piece is what size is my bike. I have googled and read and watched videos and have tried to learn how to measure my bike. Measuring the frame per the directions appears to be about 17.5" (about 44cm). The person I purchased the bike from says it is a 52cm bike. Specialized indicated it is a 54cm bike from the photo i sent them. I truly want to learn how this all works. Will someone please explain to me what I information I am missing? I am attaching a photo and perhaps it will help, or not. Thanks in advance for any information you can provide! OK, I am not sure how to inset a photo, so hopefully this works.
http://imgur.com/G29GiHr

part time waster

I find the most useful measurement is the effective top tube length.
The horizontal measurement from centre of head tube , at the top , to the centre of the seat tube ,
With plenty of frames having sloping top tubes the centre of seat tube will end up being measured to the centre of the seat post , when measuring horizontally.
A picture would be more useful , try and google the geometry of your frame , this may make things clearer.
Everyone has different set up needs, body shapes etc. Personally if your bike ends up with a 8 or 9cm stem , I reckon you could have gone a frame size smaller. Also a 14cm stem may indicate you could be suited to a larger frame size.
Plenty of people will have examples of why this is not spot on.
I'm just judging this from seeing hundreds of bikes on chaingangs , races , sportives and club runs.

bobbieocean

Thanks part time waster, I am going to my local shop next week for a bike fit (step one to solve hand numbness). After that I will check on the tube measurement as you suggest, and hopefully it is a good number. Perhaps I need to learn more about the bike fit and less about the actual size numbers. Alas, I am an accountant and numbers are my life As this is my first road bike, I am comfortable enough, but have no other experience to compare to. When i ride with a group, friends have noted my shoulders are hunched. Hopefully the bike fit will help me to understand this better, and I will stop taking the measurements so seriously. I will be googling some more today!