Originally Posted by
yashinon
This may be an open ended question but how do you know if a bike fits? I rode 54cm and 52cm Treks and could not really tell a significant difference besides the fact that I felt slightly higher up on the 54cm. On the 54cm, standing with the top tube between my legs, I had just mm's of space but it still felt OK. The 52cm felt OK also but I felt like I was riding a kids bike. I dunno maybe it was my inexperience or psychological.
Note the 54cm Trek (Madone 2.3) was endurance and the 52cm was more of a race oriented (Trek 1.2). I am interested in the endurance geometry.
The associate at the LBS felt that the 52cm fit me best and that my leg angle looked better. He stated that on the 54cm the handlebar is a tad wider also. i did feel like my arms were slightly wider apart. On the 52cm my arms felt straighter.
I can say that sitting on a road bike felt strange after riding hybrid all these years. i am 5'5" to 5'6" with 34 waist and 30 inseam.
If a bike is really dialed in well, for you, you will probably feel it. Words will come to mind, along the lines of "this one fits like a glove" and "it feels like an extension of my body." A smile will involuntarily or automatically appear on your face. You have found a dancing partner that is a hit.
There are all kinds of ideas in bike shops about fit, many of them wrong. I've heard it many times (to take just one example), that the front of the kneecap should be vertically over (or very close to vertically over) the pedal spindle, when the pedal is at the 3:00 position. This is taken as science. The more appropriate term is
BS. Here is a good demystification by Keith Bontrager:
http://www.sheldonbrown.com/kops.html
Here is another:
https://hypercatcycling.wordpress.co...pedal-spindle/
To paraphrase someone on another recent thread, "The bull**** is a little thick in this part of the pasture."
It's best to get your science from people like Bontrager, not from your typical non-scientific bike shop or youtube video.
His article would make a good study.