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What length is measured by these points?(4 posts)

What length is measured by these points?the bull
Apr 17, 2003 2:39 PM
If I measure from the steering axis centerline at the top of head tube parallel to the ground to the center line of seatpost/tube.Is this the effective top tube length or is that the top tube length?
From what I am thinking now it would be the ...the bull
Apr 17, 2003 2:50 PM
top tube length then would add 1.2 cm for every degree steeper than 73 degrees right to find the effective top tube length?
Effective top tube length is only relative, plus there's twoKerry
Apr 17, 2003 4:12 PM
The measure you note (center of head tube to center of seat tube, parallel to the ground) is the top tube length of a normal bike and the effective TT length for a compact frame. Then there is the effective TT length we talk about when COMPARING one frame to another. If one frame has a steeper seat tube angle and the same TTL as another frame, it is said to have a longer effective TTL. This is because the head tube is farther forward from the saddle, assuming the saddle remains in the same spatial relationship to the BB. The effective TTL increases or decreases about 1 cm for every increase/decrease in STA. Important to note that there is no "reference" STA against which effective TTL is compared - you just compare one bike to another.
Thanks Kerry!the bull
Apr 17, 2003 4:56 PM

I thought that was effective top tube.
But I am not sure everything gets so confusing when so many companys are measuring stuff!
I swear When someone tells me something I think about it and it makes sense then you hear someting elese and I can see how that makes sense but then I put the two together and bam confusion!But I am learning-thanks!