Seat tube angle and Math(Art?)

Triathlon Forum
1

Just curious if I determined my seat tube angle correctly. Given:
1.) Saddle is 27.5cm long/2=13.75cm to aprox. center of saddle
2.) Saddle Height=68cm from BB
3.) Tip of Saddle=0 distance from BB, it is directly over the BB
So:
STA=13.75/68=.2022(inv COS)=78.3*

2

When it comes to math I’m not the guy to ask. There’s lots of engineering types on this forum that should be able to help.

The one observation that I’ve made is if you look at Dan’s chart, assuming I’m reading it right, with your saddle position and data the chart would put you at around 77 degrees or so.
http://www.slowtwitch.com/mainheadings/techctr/bikefit.html

3

yes… you are correct sir!

4

For the mathematically challenged, if your saddle tip is directly over the center of the BB, measure the distance from the BB to center of the seat, measure the seat length and divide by 2 and use the Pythagorean Theorem (if you know 2 sides of a right triangle you can solve for all angles) to solve for the seat angle. Here’s a calculator site.

http://www.1728.com/pythgorn.htm

If your saddle tip is not directly over the BB, you need to make a right (90 degree) triangle and measure BB to center of seat, and center of seat to the point in space straight ahead and directly above the center of the BB. Use the above link to calculate.

5

"Pythagorean Theorem "

Now I remember. The last time I used it was in high school. Thanks for the url.