Originally Posted by
PeteHski
Well I'm glad you are amused, but this has actually been a useful thought process for me. I do now realise you are right about the potential issues with using a plumb bob to measure saddle setback if your floor happens to be on a slope. So I will eat some humble pie for you there and thank you for explaining your reasoning. It does make sense now.
The method I actually use for transferring a setup is pretty simple. I use a floor and wall as a reference and for saddle setback I rest my back wheel against the wall, measure the distance of the BB and saddle to the wall and subtract the two. But I do happen to have an inclinometer to check that the floor and wall are actually square. I also measure my road bike and Kickr bike on the same floor and against the same wall to minimise any reference error. I have also measured the saddle setback with a plumb bob on various floors around the house and get the same answer within a mm. So I guess my floors are flat enough, as I would have thought most hard screed floors are.
For bar drop I measure the saddle height and bar height vertically from the floor and subtract. I'm sure you would agree that a slight slope would not really matter using this method.
For reach I simply measure directly from saddle to the hoods. So the floor doesn't matter at all.
Saddle height I measure directly from BB centre to centre of saddle. Again floor slope is irrelevant.
I therefore have 4 simple measurements to transfer and only saddle setback requires a consistent reference plane. So I don't think it's very hard to accurately transfer a setup from my Kickr Bike to road bike. The biggest mistake I've ever made in this process is not having my Kickr Bike set to zero deg tilt before measuring!
I'm now curious how much on the piss your floors must be? I've just been checking all our floors with an inclinometer and they all level within the 0.1 resolution of my inclinometer.
I would also genuinely like to hear some critique of my above method and what errors would arise.
When you do a fit on a Kickr, "level" is whatever the position it has that comes out of fit. So if you move the Kickr from the fit area to a wall, you've changed the level.
When you use a wall with a floor you are adding floor level error to wall plumb error. If your floor is sloped up 1 degree and the wall is sloped in 1 degree, your saddle setback will have a combined error of 2cm too far forward, since the floor pivoted the saddle back and the wall is pivoted forward toward the saddle. The problem isn't just simple slope - walls and floor curve in ways that are hard to measure.
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.
Saddle height and saddle-to-bar are just point-to-point distances, so those are fine. But when you change setback, saddle height changes enough to matter to many cyclists, so it is not set and forget.
Without special equipment, I would zip tie the rear wheel to a vertical post and the front wheel to the downtube, then level the bike with 4 foot carpenter's level between the axles using cards under the fully inflated tires. Then I would do set back with a plumb line, recheck after saddle height, and then use the level again with a ruler to set drop from the saddle nose to the bar. Measure reach from the saddle nose to the bar, or (better yet) to the center of a stick placed across the hoods (if your bars
or hoods aren't identical between bikes). Use saddle to floor and handlebar to floor to confirm that you haven't introduced an error with the spirit level. Use a cell phone inclinometer app and a board to copy saddle tilt and bar slope.
All the same applies to the Kickr, except you never move it or reference the floor.
These methods can be very precise, but suffer a little bit from the accuracy of a bubble level, which is why I like to use a plumb line for setback instead of holding the level vertical. If you are at all sloppy with the level, nothing is going to work well.