geometry : angles

[LordOpie]

feeling dumb, probably the wine...

If the seat-tube angle is large than then head-tube angle, then geometrically, the lines would eventually cross, yeah?

For example, the Surly LHT 54cm bike has:
HT Angle degrees : 71.0°
ST Angledegrees : 73.0°

If you put a steerer tube on that bike that's 20 feet long and a seat-post that's 20 feet long, than the effective top-tube would be maybe a few inches? (exaggerating for clarification)

[LoboDelFuego]

yeah.

[Wumpus]

Sounds flexy.

[ire]

yeah.

post deleted......Nevermind, he's right

[LordOpie]

yeah.
Thanks!

So is this what's considered a "slack" geo?

Sounds flexy.
I hate you.

[Wumpus]

So is this what's considered a "slack" geo?


I would consider slack geometry something like a downhill/FR type bike with mid to upper 60's for head angles. Maybe a 70° HA on a road bike. I doubt there are many bikes besides road bikes w/ 73-74°headangles that the ST is slacker than the HT angle.


Seatutube angle is sometimes affected by tire diameter\frame size when they have to slacken the ST to fit a tire and keep the wheel base short.