I like Dan's chart a lot, but potential problems could develop in seat variation. One seat may have a longer tip than another which would give different readings. Assuming that your angle finder is a decent enough quality to be accurate, I would probably take its measurement over the chart.

It seemed like the angle finder was the obviously easy way to do it, as opposed to all the math formulas that I've seen people use, or the chart. Unfortunately, it seems that most things that seem obvious and easy have some fatal flaw that I overlook(wise old guy observation). That said, it seems like there's a long way between my saddle being 5 cm back and the chart saying 0 cm back for the same seat angle, if I'm reading it right.

doug. there are several problems at work here. first off, determining the angle by the amount of distance behind the bb the seat is problematic, chart or no ( more on this later). consider, this distance will grow and shrink depending upon how tall you are - independent of any angle change at all (!) a seat height of 3 inches would have the saddle tip in front of the bb, and 3 feet would be well behind it.

the problem with your own inclinameter number is that it fails to account for the fact that by defnition seat tube angle is the measure of the RAME, and not actually saddle position. moreover, for a given bike with a ST angle of , say , 77 degrees there could be any number of seatposts used - all with different setbacks ranging from zero to 2 in. but, the measurement itself as advertised is not taken from the seat, or seatpost, but the frame itself.

but it is not that easy - these days seattubes are not all centered on the bb. so, it is possible even a stated ST angle does not originate from the center of the bb and so could be off.

but, getting back to paragraph one, and measuring the saddle setback - this can be the only way to make a note of where YOU are at, so long as you do it for ONLY you at your sddle height. i would measure another frame of KNOWN accuracy at the seattube angle. set the height of the saddle to the same as you ride. be careful to measure from the bb itself, as bb heights themselves vary. THEN determine the setback of saddle tip to bb for that saddle height alone. make note of the seatpost setback. now set your own according to the known, realizing tha since there is no "standard" setback of seatpost the whole adherance to a specific ST angle is sort of silly. if somebody buys a bike for its "tri-specific" 78 degree seatube angle but it has a 1 inch setback seatpost the actual angle will be slacker than a 76 degree bike with a zero offset post in most sizes, for example. have fun.

well, a slight addendum. make that last sentence " many" sizes. almost half, anyway. i am 5' 71/2". for me a 1 in movement of my saddle fore or aft results in a slightly more than 2 degree angle change. taller guys would be more, shorter guys ( and many women ) would be less. did i mention that, bearing this in mind - a rider can select a new seat tube angle of close to 3.5 - 4 degrees variance just by where on the rails he puts his seat ?? if you factor in a zero offset post vs a 1" offset post PLUS the rails we are talking 6 degrees of variance, all on the same frame with the same seat tube..............that is from 73.5 to 79.0 all "measuring" the same on the spec sheet, without even resorting to a reverse post !

Thanks for the reply. This rapidly gets much more complicated than I want to make it. I realize that different seatposts and the position of the saddle, fore or aft, on any particular seat post will change the virtual seat tube angle, and I realize that the height of the saddle above the bb will change the measurement from the tip of the saddle to a vertical(can't believe that I misspelled that twice in my first post) line from the bb. Actually, the chart takes height from the bb into account. I just wanted to see where my "virtual" seat tube angle would be since I don't actually have one on a tt7, and thought that it would be the angle from the bb to the center of the saddle. When I measured that angle, it was nowhere close to the specs on the chart. What, by the way, is RAME?

ahh yes. RAME is "frame". :) well, i guess my post essentially sez that you will NEVER actually know what your seat angle is. even if you take a bike you KNOW is accurate, and cross reference it to your own the question of the original known bike's seat tube angle is dependant upon the seat post's set back. so, your own bike could be seen, for example, as a 76 degree bike with a thompson post - or just as accurately as a 78 degree bike with an american classic post. anyway, if i were in your boat i would maybe measure several bikes on a shop floor somewhere, and use the saddle tip to bb measurement ( at equal seat height ) as a gauge to place me in the same ballpark as the rest of the world and just keep track of THAT measurement. as mr empfield has been doing ith FIST, it is where you are in space in relation to the bb and controls that counts, and not what angle you term the position which matters. you could arrive at a given position in space on the bike by sevral different means, as we have seen.

For the angle finder to read correct,you need to be on level ground,it might look level but is real easy to be on a few degrees slant.Randall

"For the angle finder to read correct,you need to be on level ground,it might look level but is real easy to be on a few degrees slant."

Very good point.