Degran

So I've taken up road cycling in the past several months since March after not using a bike for almost 5 years and have slowly worked my way to doing about 125-150 miles a week over the summer. I'm currently on an old schwinn (70's) which really isn't cutting it for long distances so, I've been looking pretty seriously at getting a new bike the past few weeks before the 2011's roll in. Most of my test rides I've been doing on 54's or 56's depending on the brand but when I went to go try out a Felt F5 the other day the guy threw me on a 52. Oddly enough after putting about 5-6 miles on it in a test ride it seemed like it fit really well. I'm 5'10" with a 31.5" inseam so in theory I should be on a larger bike, right? I was just curious if there was anything different about more aggressive geometries fitting better in different sizes than standard fits. I may be over thinking it a bit but I just wanted to get some feedback on why I'd be moved from a 54/56 down to a 52 with a switch from a Trek Madonne 4.5 and a Giant Defy Advanced 3 to a Felt F5. If it feels right should I go with it or stick with something closer to the recommended size.

TL;DR

Is a 52 too small for someone 5'10" with a 31.5" inseam if the bike shop is recommending it?

Sienna19

I had good luck with : https://www.competitivecyclist.com/za...LCULATOR_INTRO
shoot for exactness with the measurements. On your rides, stem lengths and seat setbacks can make a huge difference in how a bike fits and feels. I got a road bike this year after 10 years on an ill-fitting mountain bike. I started out smaller than I should have (54) because flexibility needed to come. After a thousand or so miles, I lengthened the stem to where the fit calculator recommended after getting the seat in the appropriate position. Enjoying the ride so much more now.

DaveSSS 

Your legs are short for your height. What you really need to post is an accurate saddle height and some idea of how much saddle to bar drop you can handle.

The 52cm might fit your legs, if the head tube is at least 120mm in length, but you may need a 120-130mm stem to get enough reach, as you become more experienced.

As an example, with a 73cm saddle height, a bike with a 120mm head tube, a 15mm headset top section and a 10mm spacer will produce a relatively large 9cm saddle to bar drop with an 84 degree stem. I use a 73cm stem to produce an 11cm drop.

Your saddle height might only be 70-71cm, based on your posted inseam of only 80cm. Mine's 83cm and I'm only 5'-6.5" tall.

Spire

What you have to remember is that with sloping tubes these days, the who measurements have gotten a bit screwed up and the cm measurement is not standard across all brands anymore.

DaveSSS 

Sloping TTs have nothing to do with fit. The frame size numbers have always varied between brands. Some measured c-c, some c-t and the real oddballs like Trek and Fuji would measure to the top of the seat tube, even if it extend several cm above the TT. A 56cm Trek might fit like a 52cm in a brand that measures c-c.

If you really want to narrow down the relevant frame numbers, use reach and stack, but only a few brands list those dimensions. Even those can be misused.