Square frame geometry v...
 

When I say square, I mean the top tube, and seat tube are of same length and angle. I'm not sure what you call a frame that isn't square. Or, when the Top tube is longer than the seat tube.

Anyway, just curious if there is any advantage/disadvantage to a longer top tube.

Thanks

The arcane world of fit and fitting.
It's all about the fitting of the human body onto the bike.
The human body comes in many sizes, various leg and arm lengths.
Therefore, it follows, so should the bike's proportions.
Then there's the human fitness factor, core strength, flexibility, other things to consider.

One size does not fit all.
A long top tube, tells us nothing by itself. But when considered with seatpost setback, saddle options, stem length/rise, handlebar reach/drop, etc it becomes one element in determining an appropriate position on the bike.

BITD lots of British bikes came with 22" TTs, no matter what the ST length was. That worked well for us shorter folks with proportionally longer upper bodies than legs. I'm one of them, so my British frame can be setup to match my needs pretty easily. I feel like I'm sticking way out over the front wheel on square bikes with the right ST for my legs, and I don't like that feeling.

But I think I'm in a minority here. Square may be better for the average person.

Sheldon Brown's opinion was that top tube length was the most important characteristic for frame fit. The frame top tube length that suits you depends on both your skeletal proportions (taller vs shorter above the waist for your height) and your preferred riding style (stretched out vs more upright); while the seat tube length is related to your lower extremity length (typically measured as "pubic bone height"), but the range of preferable/acceptable sizes is perhaps greater with seat tube, since seatposts typically have a fairly large range of adjustment, and lengths available.


As philbob57 said, many English bikes seemed to come with 57 cm top tubes, while the French seemed to prefer 59 cm, in my size range anyway (59-62 cm CTT). But lots of makers, especially the custom makers, would fit or suit customer preference.

Some of us with long legs and short torsos prefer top tubes that are shorter than seat tubes.
Many small bikes come with longer top tubes as one method of minimizing toe overlay with the front wheel: Not good news if you are a short person with a relatively short torso.
Brent

I do laugh, "square" geometry was common when the seat tube was measured to the top and the top tube- center to center... so it was not really square was it?

The seat tube measuring convention changed it seems somewhere in the 80's. I blame the Italians.

a 22" ctc top tube is very easy to create a frame without toe clip overlap. even down to 21.5". below that and it required juggling dimensions.

Thanks for the posts, I was thinking that longer top tube related to more race oriented frame, while shorter top tube was more Mountain bike oriented. However I've seen touring bikes with longer top tubes. I guess if it fits is all that matters...