KOPS: saddle fore-aft, explained honestly

After saddle height, the second question is always: saddle forward or back? The classic reference is called KOPS — knee over pedal spindle — and, used with judgment, it is an excellent starting point. Used as an absolute law, it is a source of pointless adjustments. We will show you both how to check it and how much to rely on it.

1. What KOPS is

With the cranks horizontal (the "3 o'clock" position) and the forward foot in its natural pedaling position, KOPS says the kneecap of the forward leg should fall roughly over the pedal spindle. The vertical between the two is the reference: knee well ahead of the spindle = saddle probably too far forward; well behind = probably too far back.

2. How to check it at home: the plumb-line method

• Bike on a trainer, perfectly level; pedal 2–3 minutes so your position on the saddle is the real one, not a staged one
• Stop with the cranks horizontal, the measured leg forward, foot in its normal pedaling position
• Hold a string with a small weight (a nut is enough) at the front edge of the kneecap
• See where the string falls relative to the pedal spindle: ahead of it, on it, or behind it
• Repeat 2–3 times — saddle position naturally varies by a few millimeters

3. The honest part: what KOPS tells you and what it doesn't

KOPS is a useful convention, not a biomechanical law — fitting literature has long treated it as a starting reference, not a mandatory target. Perfectly functional positions live with the knee slightly ahead of or behind the spindle: triathlon and time-trial riders sit deliberately far forward, endurance positions often slightly back. What the check really tells you: if you are far from the reference without a deliberate reason, saddle fore-aft deserves a conversation. What it does not tell you: that you must sit millimetrically over the spindle.

4. How to work: small steps, on the saddle rails

Loosen the saddle clamp, mark the original position on the rails, move 2–3 mm at a time, and ride before the next evaluation. Most saddle rails have graduations — use them as reference. And an often-forgotten detail: saddle tilt gets re-checked after every re-tightening, with a phone level across the middle of the saddle.

5. Where the app comes in

Our video analysis currently measures the side-view angles (knee, elbow, hip) — we do not measure KOPS yet, because it requires a precise static frame at "3 o'clock" and a calibrated vertical reference; it is on our development list, and we will ship it only when we can measure it to the same standard as the other angles, with a confidence indicator. Until then, the plumb-line method above is exactly what fitters use — and after any fore-aft adjustment, the knee angle analysis confirms your height is still right.

General, indicative guide. For special positions (triathlon/TT) or persistent discomfort, a professional fitter remains our recommendation.