Originally Posted by
DaveSSS
The reach difference has to be due to the saddle position, relative to the BB. Use a plumb Bob to check the nose of the saddle, relative to the BB.
Carefully check the saddle height on both bikes, from the center of the BB.
I measure the saddle to bar drop, vertically from the floor. If one is less than the other, just remove spacers to make them the same. Stems lengths can be measured differently and the angle also affects the horizontal length.
There could also be a mistake in the bike geometry charts.
Start with the saddle fore/aft and height and go from there.
I've measured the saddle position (height/setback) many, many times, and everything checks out. And my body lets me know pretty quickly is something is off with my saddle, so I'm confident that those measurements are correct, and the same on the two bikes.
Then I've measured saddle-to-bar drop from the floor, along with a laser level along the handlebar plane...I keep getting the same number, as well. Stems were also measured, and both are 100mm. Technically speaking, the -12 stem should have a slightly longer reach, yet that is the bike that is coming up short.
I've run out of spacers to remove, and, as mentioned above, I'm more concerned with
WHY the numbers aren't lining up, when the math says that they should...I shouldn't have to run a -17 stem, and a low-stack top cap to account for a 12mm difference in frame stack.
I'm going to have to assume that something is off with the geometry chart, as well
Originally Posted by
grizzly59
The reference point on the saddle should be something like where your seat bones sit. Saddles have different length noses and tapers.
Same exact saddle on both bikes, so measuring from the nose works