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A DIY bike fit with your phone

July 22, 2026 · 6 min read

A professional bike fit measures a handful of joint angles while you pedal and adjusts the bike until they land in proven ranges. The measuring part no longer needs a studio: a 20-second video on a trainer and a pose model will give you the same five angles fitters start from.

The five angles that matter

Knee extension at the bottom of the stroke

The saddle-height angle. At the 6 o'clock pedal position your knee should keep 34–48° of flexion from straight. Less than that (leg too straight) usually means the saddle is too high — a common cause of posterior knee pain and rocking hips. More flexion than that means it's too low, loading the front of the knee.

Hip angle at the top of the stroke

The closed angle between your torso and thigh when the pedal is at 12 o'clock — the tightest your hip gets each revolution. Fitters look for roughly 44–58° on a road position. Too closed and you'll feel it as hip impingement or a rocking pelvis; it's driven by saddle height, saddle setback, and how low your bars are.

Torso (back) angle

Measured from horizontal: 40–50° is a relaxed endurance position, 30–40° race-oriented, and TT/triathlon positions drop to 5–30°. Lower is more aero but demands more hamstring and back mobility — chasing a pro's back angle without a pro's flexibility is the classic self-fit mistake.

Elbow angle

On the hoods, elbows should be softly bent — about 15–30° of bend, never locked. Locked elbows usually mean the reach is too long, and the road buzz goes straight to your shoulders. On TT extensions the elbow sits near 90–110° instead.

Ankle angle

The shank-to-foot angle stays near 90° (±15°) through the stroke. Excessive toe-pointing can be a sign the saddle is too high — the ankle extends to reach the bottom of the stroke.

Measure yours in five minutes

1. Put your bike on a trainer, camera at hip height, square-on to your drive side, far enough back to see the whole bike.
2. Warm up for a few minutes first — your position after 5 minutes of riding is your real position — then film ~20 seconds of steady pedaling.
3. Drop the clip into the analyzer, press Get Poses, and apply the Cycling — road fit preset (or TT / aero).
4. Read the chart against the target bands: the knee curve's minimum each stroke is your bottom-of-stroke extension; the hip curve's minimum is your top-of-stroke closure; torso, elbow, and ankle should ride inside their bands throughout.

Adjust like a fitter: one change at a time

Saddle height moves the knee angle roughly 1° per 3 mm. Make one small change, refilm, and use Compare to see both clips on one timeline — the before/after difference shows up in the curves immediately. Chase comfort first, aero second.

A DIY check like this catches the big, common problems — saddle far too high, reach far too long. Persistent pain, numbness, or saddle sores after your position is in range are the cue to see a professional fitter, who brings things video can't: cleat wedging, saddle pressure mapping, and a trained eye.