How small is too small?
 

Found a Vintage frame that I'm currently obsessing over. At first glance it seems too small but checking out the specs it's very similar to my current ride. I'm 6' 2" with short legs and long torso. Is 55cm seat tube and a 57cm top tube too small? If it matters, I like long rides with a few hours in the saddle. Will my middle age body be able to handle it?

is the top tube slanted to the rear any amount?
if so, Ignore the Seat tube spec completely.

i measure a phantom "top tube" in a horizontal plane... center of seat post to center of head tube.

57cm sounds about right for you.. or a 58, with a stem length you choose.
the angle of the seat tube and head tube also play into proper fit.... some diverge, others are the same angle......

I am shorter than you and the 55 cm Look 481SL that I thought would be perfect for me turned out to be too large because of its 57 cm top tube. That bike might be very good for you
I was able to trade frames for a 54 cm, perfect

You'll likely be able to handle it. Make sure it's really what you want. After thinking bikes from the 70's were the best thing for over 45 years, I finally found out in 2020 that I was mistaken and enjoy the new bikes more.

Too little info to make a realistic projection on fit. Roadie, city bike, mtb? Preferred position on bike = upright or aero?

I'm 6'1" and ride road bikes with 57cm Effective Top Tube, but they need a 13cm stem to feel right. If your 'wingspan' is greater than your height it might feel cramped or result in an upright riding position. You clearly won't be able to stretch out and get aero without a long stem.

Even when jonesing over a particular bike, it will only squash your obsession with a bad fit. A small fit, depending on the geometry of HTA and front-center, might be twitchy in handling.

What vintage frame? Why should that be a secret?
Vague questions beget vague answers

is it a secret...or is it just not specified because the OP thought it's beside the point?

https://cimg8.ibsrv.net/gimg/bikefor...63897fa59.jpeg

Well, we know it is not a Vintage bike - sloping top tube. Butt,... if wrong then a 55cm frame is too small for someone 6'2", even with shortish legs.

55X57 sounds like a custom roadie, or a rigid mtb (many had long tt), or sloping top tube (most likely for a road or mtb).




OK - maybe with a long seatpost, long stem - the obsession could be rideable. See also: Circus bike thread.

It’s too small.

How short? Measure your cycling inseam.

Neither leads to good answers.

(It’s effectively a secret even if that wasn’t the intent.)

Sorry all, I wasn't trying to be intentionally vague. I'm still learning the ropes over here. It's a 90's Clark Kent Titanium. I appreciate all the insight and knowledge.

ok.. the clark kent bikes usually had high bottom brackets, and level top tubes... that might explain the shorter seat tube specification you mentioned, eh?...

your short legs with long torso might fit the bike very well... a bit longer steering stem, and a rearset seat post may be a good idea... the seat tube angles look to be close to, or the same as the head tube angles...

you might want to test ride a couple 58 and 60cm frames too... sadly, most larger frames lean toward long legs and short torsos, from what i've seen.. i always end up on a small-medium frame with a fairly long stem, and the seat slammed back.

How small is too small? I bet some women might have an opinion. :)

(I don’t write the leading headlines.)

I'm 6'3", so only and inch taller, inseam is 34.5 inches and my go to frame size is a 61cm, at least with the classic horizontal top tube geometry. That gives me plenty of adjustment room and is not the largest size frame I can ride comfortably but rather the best overall fit. I used to ride a 58cm but I eventually realized that was too small and short. I needed to have the seatpost too high and the bars were too low, uncomfortable for long rides. My brother is 5'10", also has average length legs and rides a 56cm while being able to fit up to a 58cm. I think his inseam is around 32-ish inches. I recently built up a 58cm frame (with horizontal top tube) for a friend who is 6 foot with a 32.5 inch inseam and that bike fits him quite well. Another friend rides a 58cm (again with horizontal top tube) who is 6'2" but he has slightly shorter legs than me and is young and can handle being leaned over more on the bars than I can and rather likes the aggressive position.
Sorry but I don't have any of the top tube measurements handy or memorized, just the seat tube measurements and all of those are as measured from center to top.
Hopefully those data points can help you in understanding how well you might fit a 55cm.

Can't you just compare the bike's specs/geometry to the bike you currently ride, making sure to use horizontal or effective top tube if either or both are slanted TT? If it's close but not quite, you also need to look at the seat tube angle because that affects the fore/aft position of your saddle and therefore the reach from the saddle to the handlebars.

Everything else based on height and other's opinions are just speculation while you can actually make a good comparison and decision for yourself, if you have a bike already that fits you well.

If it is similar in design to this 58cm Kent - with level top tube - the 55cmX57 will not ever fit 6'2" humans well.
FWIW - 6'1" and 60 cm frames are my sweet spot with 58-59cm top tube and 11-12cm stem.
https://cimg8.ibsrv.net/gimg/bikefor...45efdd9be7.jpg

The term I see often is “Effective Top Tube”. Or “Horizontal Top Tube”. Mostly referring back to the olden dayes when a top tube was parallel to the ground,