Originally Posted by
Robert A
I'm 5'6" and my inseam is 30". Irrespective of this, where do I go to find my ideal stack and reach? Are there online tools? I'm in Los Angeles, and Helen's does bike sizing for free, but I'm not looking for something that's part of the sales process. Bike fitters are, I believe, are something you do AFTER you already have the bike.
How do experienced cyclists get sized correctly?
Bike fitters absolutely can fit you BEFORE you buy a bike, and can make specific sizing recommendations for particular models.
Everybody else just uses rules of thumb. If you look at many companies fit charts, you'll see height recommendation ranges for sizes:
https://www.trekbikes.com/us/en_US/b...meset/p/16701/
Trek says someone 5'6" should be on a 52 or 54. You have a shortish inseam for your height (if it was measured accurately), so it seems odd that you would need a 51cm top tube, which are generally only found on 49cm frames and smaller.
If you're going to get fit anyway, get fit first - the numbers should be easily transferable to a new bike of the correct size. When I worked for a fitter he provided this service all the time using a shop bicycle to get numbers and make a sizing recommendation among whatever model choices. If the patron decided to buy a brand we didn't carry, we'd look at the charts for that model and recommend a size, and they would still bring it back for a final fitting where we dialed it in.
If you just want an answer - buy a 52 (or 53 if odd sizes). And that's a "real" 52, not a Colnago 52
S or other non-standard sizing systems. Look for models with moderately tall headtubes as they will make it easiest to get the bars as high or as low as you want, if you don't already know what you want.
Here's a whole thread that shows a great degree of correlation between height and frame size:
How tall are you and what frame size do you ride?