Originally Posted by
Sojodave
I'm 6'4" with a 36" cycling inseam and I ride a 61cm frame. I'm a believer in Greg Lemond's saddle height formula of inseam x .883. This will get you close. I'm at exactly 80cm for saddle height. I ride a short-nosed saddle Pro Stealth. My setback is 110cm from the bb. I got frustrated with the balance test because I thought my balance was about the same regardless of how far I had my seat forward or back. Here is a good video on setting the fore/aft.
https://www.youtube.com/watch?v=SZhWVZq2qUc
Balance test or method is often discussed and even brought up in Stegg Hogg's excellent article. Reality is...and Chi touched up this...varies by rider...even riders the same size.
Size, power and really riding objective of rider...tourer, endurance rider versus Crit racer. There is a reason that Specialized makes their purpose specific Crit bike, their Allez Sprint with more upright seat tube angle versus their other famous race bike the Tarmac with a seat tube angle more angled rearward to get the rider back a bit more. Same company, different geometry. Both race bikes.
As a general rule and to reinforce Chi's comments, a lighter, stronger more aggressive rider will prefer a more forward position....in general but no absolute for sure. Further a more forward position allows to get more aero because the pelvis is closer to the BB horizontally which allows more forward pelvis rotation. A TT bike is of course the ultimate manifestation of this dynamic but rider's torso is supported by the elbows for that reason...not really a sustainable position relying on the core or the hands to hold up the torso against a TT position.
I mention Sheldon Brown from time to time because I asked him a general rule about KOPS. He said its a bit of a flawed convention as most that are into bike fit know...but he said in general, racers want to be at KOPS a bit in front of it and more average riders, tourers, distance riders with reduced pedal forces and more upright position want to be a couple of cm's behind it. Of course being behind it typically means a more upright riding position because its harder to rotate the pelvis the farther behind the BB.
OP, hope that makes sense. Depends on your power to weight and how you ride...aggressive rider or more smell the flowers type of rider. Keep in mind, the harder you push on the pedals, the more the weight is reduced on your hands. This allows a more forward position on the bike which btw is conducive to more drop. Best riders I have ridden with where I can barely stay on their back wheel, they have very little weight on the saddle. A saddle is more of a perch to real fast guys...not a lazyboy.
Fit is a puzzle and the pieces do fit for each rider once the puzzle is solved which is the aggragate of many factors discussed. I can ride a wide variety of setback...way back to pretty well forward. I end up mostly in the middle of the rails with a 25 deg setback and 73 deg sta with 77cm saddle height. A common pro position in terms of setback...they all run more drop than me and some run less setback...varies by rider.
Another data point you guys may appreciate on the subject:
Here is a chart for setback from B. Hinault's book and was used by all of Guimard's riders (Hinault, LeMond and Fignon). Measurement is from the tip of the saddle nose to centre of BB measured horizontally.
Cycling Inseam versus Saddle Setback
75 to 78cm. 4 to 6cm.
79 to 82cm. 5 to 7cm.
83 to 86cm. 6 to 8cm.
87 to 90cm. 7 to 9cm. My cycling inseam is 35.25” saddle height = 89.5 cm...so my sweet spot is ~9 cm +/- which works pretty well.