Originally Posted by
Kontact
For drop, if the floor isn't level, your method for bar drop will definitely be in error. If the floor sloped by 1 degree, your drop will be off by about 1 cm because the saddle is close to the rear wheel and the bar close to the front. So they will have a large slope built into them from the floor.
I still don't get this. I am just measuring the saddle and bar heights vertically relative to the floor plane. A 1 deg floor slope may lead to an error of approx 1 mm over a metre if I measure vertically at 89 deg rather than 90 deg . But my floor is much less than 1 deg out anyway. This is not the rise over run error discussed earlier when measuring setback with a plumb bob.
Actually the error would be tiny as both height measurements would be at 89 deg, so the error would be their difference i.e. bar drop x cos 1 deg
In practice using this method to measure bar drop I find that the important thing is to make sure the bars are level in the front view, which I do by measuring their height at both ends.