bike geometry re: short and taller riders

[Cataboo]

Tri bikes with the larger seat angles use a different set of muscles than a normal bike - You pedal more with your quads on a tri bike. Whereas a regular bike uses your quads and hamstrings.

So a tri bike saves your hamstrings for running.

I'm 5'1 - I like a 73 degree seat angle on my bikes... that seems to be where I'm comfortable & pedal efficiently. I've had 74 & 73.5 degree seat angle bikes and they always seem to make me hang my butt off the back of the seat to get comfortable.

my surly has like a 75 degree seat angle... and I'm getting used to it, but don't like it for long distances, I end up hanging my butt off the end of the seat.

They put larger seat angles on smaller bikes to shorten the top tube & reach for smaller riders...

[wildeny]

They put larger seat angles on smaller bikes to shorten the top tube & reach for smaller riders...

This answer wnyrider's wonder. The seat tube angle of my Fuji Finest RC XS is 76 degree. I'm all right with that.

And the design of tiathlon bike is different from road bike. Check this link.

Cervelo uses different approach to shorten the top tube length for small riders: reduces the head tune angle.

[Kathi]

Here's an explanation to your question. This is from the Titus Bicycle website.
This information is for cyclists 5'5 and under.

"When it comes to fit, a true woman specific design will feature adjusted angles and geometry to fit a female’s body dimensions. Aside from a shorter top tube needed for a comfortable reach and increased standover, the seat angle should be steeper to accommodate a woman’s shorter femur length. The steeper seat angle position allows a woman to be positioned properly over the pedals. The average seat tube angle for both road and mountain non-female specific designs is typically between 72 and 73.5 degrees. The seat tube angle on female specific designs should be between 74 and 75 degrees. This steeper seat angle also contributes to better handling. A steeper seat angle results in a longer, more stable wheelbase. Anything that can be done to get the wheelbase a little more stretched out on a small frame will result in a more stable, better handling bike."

http://www.titusti.com/womensfit.html

I don't know if the short femur theory is true for every small woman but I'm
5'1" and all my bikes have the steep sta including my custom frame.
Without the sta there is no way I can get correct saddle setback or (KOPS). Even with a sta I require a zero degree seatpost and my saddle has to be set forward in order to achieve correct knee positioning.

[Cataboo]

I must just have weird femur leg lengths.

I'm 5'1, I use a set back seatpost with my seat all the way back and can get comfortable leg wise on a 73 degree seat angle. 73.5-75 degree seat angles, even with the setback & the seat all the way back, my legs are just not in the right position. I don't use WSD's because I find the top tubes too short - so my top tubes usually about 540 mm with a 100 mm 6 degree stem & standard reach handlebars. I usually use about a 48 cm frame.