How to Set Saddle Fore-Aft Position

• Balance and hand pressure. Moving the saddle back shifts more of your weight rearward; moving it forward puts more weight on your hands and arms.
• Effective saddle height. Because the seat tube is angled, sliding the saddle back also moves it slightly further from the pedals. A large rearward move can call for lowering the saddle a little — re-measure after any fore-aft change.
• Reach to the handlebars. Sliding the saddle forward shortens the distance to the bars, and back lengthens it — which is why fore-aft is often misused to fix a cockpit that is too long or too short.
• Muscle use and comfort. Riders often describe a more rearward position as more "seated and powerful" and a more forward one as more "on top of the pedals". These are subjective impressions and vary between riders.

The traditional rule, KOPS (Knee Over Pedal Spindle), drops a plumb line from the front of the knee with the cranks horizontal and moves the saddle until the line passes through the pedal axle. It is simple and still widely repeated.

It is also widely criticised. In his essay "The Myth of K.O.P.S.", frame builder Keith Bontrager writes that the rule “has no biomechanical basis at all” and is, at best, a coincidental relationship that puts many riders somewhere near a workable position — not a reason to set the saddle there.

1. Start with the saddle centred on its rails (most rails have a marked range) and the top level, with your saddle height already set.
2. Mark the current position on the rails with tape or a marker so you can always return to it.
3. Ride on a trainer at a steady, moderate effort with your hands on the hoods. Notice whether you feel pushed forward onto your hands, or sliding back off the saddle.
4. Move the saddle in steps of about 5 mm in the direction that relieves the problem, then re-check saddle height, because moving fore-aft changes it slightly.
5. Give each change several rides before judging it.

Dan Empfield (Slowtwitch) analysed professional road positions and proposed a predictor for the distance from the saddle nose to the hoods, from rider height (H) and saddle height (D):

For road bikes, the bike fit calculator shows this saddle-to-hoods value alongside your saddle height.

Aero bikes put the saddle much further forward relative to the bottom bracket: in his static tri-fit system Empfield uses an effective seat angle of about 79.5°. Rules developed for road positions do not transfer to aero positions. More in TT and triathlon bike fit.

After any fore-aft change, re-check your knee angle with the riding position check — see the knee angle guide for target ranges. If you are starting from scratch, set your saddle height first.