Originally Posted by
Nessism
Most all standard racing frames built in the last several decades have head tube angles between 72 - 74 degrees. Fork rake works with the HTA to determine trail - which ranges from 5 - 7 cm. This range has been determined imperially and has held up to the test of time.
Chain stay length has a small effect on weight balance on the bike, and bottom bracket drop has a small effect on center of gravity placement. Again, common range for frames is quite tight because it just plain works.
One small Nessism I'll though out is somewhat controversial; I contend that a bike with a low bottom bracket will steer faster than one with a higher BB. The low BB lowers the center of gravity and moves said CG closer to the roll axis of the bike - thus making it easier to turn and lean.
Enjoy your research.
Well, the higher bottom bracket height is for the only purpose of being able to pedal through the turns... the tight ones, without scraping your pedals on the ground, and at the very least start to pedal sooner coming out of it. (All my pedals from my racing days are deeply scarred despited the higher BB). The higher BB has minimal effect on maneuverability... certainly nothing to the amplitude of good versus bad geometry on the rest of the bike. Your weight, no matter at what height, is in line with the lean of the bike and the contact patch on the ground - it makes no difference at all - and this was a common misconception among many framebuilders of the 70s. They thought that a lower CoG on a car, can be transposed onto a bicycle - bit a bike leans, a car doesn't. It certainly has nothing with good versus bad geometry on the rest of the bike. Where I will make a concession, that there is a perceptible difference, is that when your body is higher, while it leans in at the same angle, the distance it moves is a bit wider, to create that angle.
I've noticed that a bike with extremely short whelbase, including short chainstays, and a top tube shortened to the point that your toes touch the front tire when turning, does turn better. The quicker turns are more apparent at lower speeds, in tight criterium turns, and on track racing on a tight track (in Montreal we had a 333m velodrome with a 49 degree inclination in the banks)... but I have also noticed that it has helped me take a turn, going down Mount-Royal, at 100+km/h, a turn in which another bike failed, ending in a bad accident the year before.
Amazing handling sometimes comes at a cost: the shorter rear chainstays make for a little too much weight on the rear wheel. This may allow for speed wobbles when going down hills at high speed. You need to shift your weight forward, leaning over your handlebars, to make those go away. It's manageable, but feels dangerous when you're in a tuck, pedaling full-force against the rushing air.
In the criteriums, I could outmaneuver any Marinoni or other bike in the pack. They all used that 1972-devised (by Cinelli) frame geometry. That's why I miss it so much. It was just the right balance of everything.