I'm about 5'10" and on a 55cm frame. I know there are a bunch of different factors leading into fitting a frame correctly, but is this about average for most people out there or are they riding 57cm? thanks

5'10" on both a 55 57 and a 62, depends on the frame.

I am 5-11" and I ride 55-56cm "nominal size" bikes. That translates to anything from 55-57cm effective top tube though. Size a bike by effective top tube, as that's really the only metric that matters. Seat tubes are a somewhat irrelevant way to size because (1) conventions are not consistent with respect to center to top/center sizing and (2) the introduction of compact geometry (sloping top tube) frames.

55 cm *generally* sounds about right for a 5'10" rider. But if you know the bike brand, then it's best to look up its geometry and be familiar with its "stand-over height" and its top tube length for your personal reach. There should be about a 1-inch clearance between the bike and you (in your shoes), and you should not have to reach too far to touch the handle bar.

sounds crazy. i'm 5'11" and my capo is a 52cm. it does not fit improperly. however i realize the capo 52 geometry is like most other makers' 54's.

heres a good intro

https://www.peterwhitecycles.com/fitting.htm

Its that top tube. IME, the TT length is the tell-all for bike fit. I've got a pretty damn short torso - 5'10" with a 34" inseam at my natural waistline - and the TT is usually all I need to know about the frame to decide whether it'll fit or not. Everything else can be adjusted or swapped out, but if that extension is too long or short, you're boned.

I'm about 5'11.75" - 6' and ride two 58cm and a 56cm road bikes

Hey Slick. Does it fit ya? Are ya Comfy? if so whocares. I ride a 56cm and I am 5'10" but have short leggs. My brother who is the same height has longer leggs by 2 inches we both ride a 56cm...Stem cures many a problem.
In a Tri bike I am riding a smallish 54cm but thats the way it is supposed to be...
Just ride and be happy...Frame vary from brand to brand.

BTW!
I forgot, I just got a new Bianci 928 carbon...Sweeeeet bike size 58! Crazy Italians.....top tube is same lenght as my 56 cm Eddy Merckx.

6' 1" and use to ride a 54cm BK

5'11 and i ride a 55 and i think it fits about as good as a bike can, but what do i know.

6'0 and ride a 55. I tried a 57 but the 55 just felt better. I've got a short inseam though - 32"

Who the f*** knows though? I'm sure some people have bike fitting figured out, but for me it's always been perplexing.

I'm 5'10" as well and I tend to look for bikes with a 55cm top tube as a starting point but you really won't know if the bike fits until you try it...
Besides, test riding is fun...and an excellent way to check the work of a given shop's mechanical staff...
I chose not to buy a Bianchi last summer because of the horrible way it was set up at the only store that had them in stock in downtown Toronto (creaky BB, wheels not trued, poor chain tension etc.)...

5'10" 11cm stem on the bike with the 54 cm top tube, 10cm stem on the bike with the 55 top tube. You get the idea.

5'10" on 55 is a bit on the small side but if you can try a 55 and 57, you'll easily figure out which one will fit more appropriately. some people just like their bikes smaller.

Yes.

5'9" on a 54cm road frame and 53cm fixed.

Depends on how high up your balls are. I'm 6'3" with a 34" inseam...so my balls are pretty high up there..because I'm so damn manly. I ride a 62cm IRO Angus.

If your balls are pretty high that means they haven't dropped yet, making you less manly.

^^^ hilarious. i am 6'4" and ride a 59 and a 62 with a 120 and 110 reach quill on each respectively. the reach is pretty similar because of this on both and i feel comfy.


[EDIT]

it should be noted that they are non-sloping TT and nearly identical geometry.

aww shucks...ya got me!

I am 5'10" and ride usually around a 55. It depends on the frame maker.