Perhaps I'm a little dense this morning, but I can't figure out the seat tube length figures on this geometry chart. Except for the 57cm (XL), are the numbers in columns A1 and A transposed or not?

http://www.lookcycle.com/products/data/geometrie/geometrie555.pdf

J is the seat angle. The seat tube length are all in A2 A1 & A. A2 is what is normally given as seat tube, from c of bb to c of tt but each manufacturer lists is differently. Some go from c of BB to top of TT. I would most concerned with A since that will dictate how much post is showing. If you use a thomson setback post with a bent post providing setback, you would need to know how far the seatpost is going to be inserted in the frame so you can actually use the thomson setback post.

Thanks—but looking at the drawing and then checking the numbers for the S, M and L frame, shouldn't A (BB center to top of seat tube) always be longer than A1 (BB center to center of horizontal top tube)?

The "recul" (setback) headings have moved out of place on the chart, but that's easily figured out.

Thanks—but looking at the drawing and then checking the numbers for the S, M and L frame, shouldn't A (BB center to top of seat tube) always be longer than A1 (BB center to center of horizontal top tube)?

The "recul" (setback) headings have moved out of place on the chart, but that's easily figured out.


The drawing is confusing because it is not drawn with the typical amount of slope. A1 is the c-c frame size, for a "virtual" horizontal TT. With enough slope, both the actual seat tube length, A and the A2 dimension will be smaller than A1.

The only dimensions of any relevance are the head tube length K, the seat tube angle J and the total seat tube length A.

The drawing is confusing because it is not drawn with the typical amount of slope.

Thanks, makes perfect sense now. I confused myself by putting too much trust into the drawing and not enough into the numbers.

The only dimensions of any relevance are the head tube length K, the seat tube angle J and the total seat tube length A.

What he said. Seat tube length bears no relevance at all, except possibly for aesthetic reasons.

What he said. Seat tube length bears no relevance at all, except possibly for aesthetic reasons.

Who said that?