I'm looking at a couple of bikes, of course online cause no one stocks these bikes nearby, and one mfg refers to Effective Top Tube Length and the other uses Horizontal Top Tube Length.

I'm thinking these are one in the same?

Yes..

I'm looking at a couple of bikes, of course online cause no one stocks these bikes nearby, and one mfg refers to Effective Top Tube Length and the other uses Horizontal Top Tube Length.

I'm thinking these are one in the same?

Generally you're right, but the term has also been applied when comparing bikes with different seat tube angles. Roughly, one additional degree of STA means that the head tube will be 1 cm farther forward, all else equal. Since you set your saddle position relative to the BB, this means greater reach on the bike with the steeper STA (assuming both bikes have the same top tube length).

Do the numbers quoted for ETT look like typical top tube lengths? Some folks use effective top tube to mean the amount of the top tube forward of a vertical line drawn through the bottom bracket. It is used this way to see what the true "reach" of a frame is, regardless of the seat tube angle.

Do the numbers quoted for ETT look like typical top tube lengths? Some folks use effective top tube to mean the amount of the top tube forward of a vertical line drawn through the bottom bracket. It is used this way to see what the true "reach" of a frame is, regardless of the seat tube angle.

I have never seen ETT used this way, what you describe has been called "reach" and it remains the same regardless of STA. That's because saddle position is fixed from the same location also.

Do the numbers quoted for ETT look like typical top tube lengths? Some folks use effective top tube to mean the amount of the top tube forward of a vertical line drawn through the bottom bracket. It is used this way to see what the true "reach" of a frame is, regardless of the seat tube angle.


As already noted, what you are describing is the frame reach. The term "effective" is really a misnomer. Horizontal is the correct term. A drawing of frame reach would lead a person to think that the seat tube angle does not affect the frame reach, but with the information provided on most geometry charts, the STA is needed to calculate the reach. Very few manufacturers list a reach or stack height measurment in their geometry charts. Until they do, you're just as well of comparing TT lengths and adjusting for differences in the STA. The discussion linked below explains why reach measurements can also be misleading.

http://forums.roadbikereview.com/showthread.php?t=122024

Also, as already mentioned, the term effective has been applied when comparing two frames with different seat tube angles. The two frames might have the same TT length, but if one has a 1 degree steeper STA, it will have an an effective top tube length that is about 1cm longer. I quit using that term, because it confused people. Perhaps comparable is a better term.