Originally Posted by
dayvurd
okay so the dimiter of my downtube is roughly 10cm...so i divide that by 2 = 5. then the distance from the chainring tooth to the seat tube is 3.4cm. so that gives me a total of 8.4cm?
No because your down tube and seat tube are likely to be different diameters.
And also no because there is no way your down tube is 100mm diameter.