What I was talking about here was bikes with taller or shorter headtubes extending _down_, so with the same stack height.
Imagine for a second two rigid bikes with identical stack and reach:
One with a 27.5 wheel and one with a 29er wheel. The 29er would need a shorter head tube to keep the fit the same, since the crown of the fork is higher above the ground.
Therefor the 29er would have a longer downtube, even though fit was identical.
That’s all I meant.
If you are comparing bikes with the same travel forks and wheel sizes, then yes, (effective) downtube length is an easy number to grab and compare.
May 28, 2019, 7:24 a.m. - Tjaard Breeuwer
What I was talking about here was bikes with taller or shorter headtubes extending _down_, so with the same stack height. Imagine for a second two rigid bikes with identical stack and reach: One with a 27.5 wheel and one with a 29er wheel. The 29er would need a shorter head tube to keep the fit the same, since the crown of the fork is higher above the ground. Therefor the 29er would have a longer downtube, even though fit was identical. That’s all I meant. If you are comparing bikes with the same travel forks and wheel sizes, then yes, (effective) downtube length is an easy number to grab and compare.