Originally Posted by
Phatman
...I have a weird issue where I have a bit of trouble switching between bikes. I feel uncoordinated, my pedal stroke feels sloppy and my knees bug me for the first couple rides on each one. If I ride one exclusively for a week or so, I seem to get used to it and I'm fine, but if I switch back and forth, say, every other ride, I never really get comfortable.
Its weird, because the setups are very similar. The only position differences are 172.5mm cranks vs 175mm on the graveller, and an extra 10mm of stack on the gravel bike. I've adjusted the seat height and setback on the road bike to accommodate the crank length, so at full extension, the seat height should be the same. The pedals/shoes are different too, speedplays vs SPDs, and I've adjusted for the different stack heights. Obviously, the geometries are very different, but where my hands/butt/feet are should be very close to the same.
So, before I answer question, I'm going to ask: have you ever had a bike fit? One more: have you considered getting a fit for the specific discipline? Bike fit, and position, is different depending on the riding you're doing. You knew that, I'm just reiterating.
Typically, if you use the same crank size on all of your bikes, you just measure from the center of the BB to the top of the saddle, and replicate that on every bike (assuming you also have the saddle at the same position fore/aft to ensure your knees are making the same motion on both bikes). However, with differently sized cranks, I measure from the pedal at the bottom of the stroke to the top of the seat, then I ride it and make small adjustments based on how it feels until (a) I don't feel like as I pedal, I could push my foot lower, and (b) my hips aren't rocking when get to the bottom of the pedal stroke. I suspect that the feeling you are experiencing is because the saddle to pedal distance is just slightly different between the bikes.
My positions, in terms of saddle to bar drop are different on the bikes, too. But, I don't think that's your issue.