Originally Posted by
Randochap
Very relaxed angles for a short person will also make it next to impossible to follow the "knee over the pedal axle" orthodoxy (not that I'm a follower of convention). You will find your knee well behind the pedal axle. This is fine for relaxed, comfy riding, but does limit overall power. Again, the answer, of course, is very short crank length.
These are not "dodgy" observations This is what I experience, comparing my bikes from both categories.
A very relaxed seat tube angle is just what a short person NEEDS in order to achieve KOPS. 99% of bikes built for small riders place them FAR in front of KOPS in fact most small riders have less saddle setback than the supposed minimum of 5 cm set by the UCI.
I ride with an effective seat tube angle of 69º just to achieve KOPS.
I've only seen vintage bikes that come close to fitting short riders properly off the shelf. I initially thought I had invented something new when I built my custom bike and finally found out how to build a bike to fit short riders but then I came across a few vintage bikes and there it all was. Short cranks, really relaxed seat tube angles and small wheels.
The principle of what I did/ what I promote is proportional fit. Small riders fit bike in EXACTLY the same way that larger riders do so all the same rules apply. Starting from getting cranks that are proportionally correct.
I have a couple of 24" wheel mountain bikes from the 90's which are pretty good with 150mm cranks, relaxed seat tube angles and reasonably short reaches (BB to HT) but by and large manufacturers have just forgotten how to build bikes for small riders and now they simply don't want to remember. I costs them money to do it right.
Lots of people say that what they have is fine but without having something thats perfect to compare it against you can't really tell.
And back to where I came in. A 48cm, 700c, standard bike is OK for the OP but not great. It could be better and I've definitely seen worse.
Anthony