Bicycle Fit
Most cyclists ride bikes that don’t fit. The stock bike from the shop approximates fit based on height, but bodies vary — leg length, arm length, torso proportion, flexibility. A properly fitted bike feels like an extension of the body. A poorly fitted bike creates pain that accumulates over miles: knee aches, numb hands, sore neck, lower back strain.
Fit isn’t about comfort in the abstract. It’s about power transfer (efficient pedaling), injury prevention (sustainable position), and control (stable handling). Get fit wrong and the body compensates with patterns that cause trouble over distance.
The three contact points define fit:
Saddle: Where your weight sits. Height, setback, and angle matter. Handlebars: Where your hands rest. Reach, drop, and width matter. Pedals: Where power transfers. Cleat position and foot angle matter.
Everything else — frame size, stem length, spacers — serves to position these three contact points correctly relative to the rider’s body.
Fit is iterative. Small changes reveal whether you’re moving toward or away from optimal. A 5mm saddle height change feels wrong initially (the body adapted to the old position) but may feel better after adaptation. Changes need riding time before evaluation.
Saddle height is the most critical single measurement. Too low wastes power (the leg can’t extend) and stresses the knee (the joint works through an inefficient range). Too high causes rocking hips (overreaching at bottom of stroke) and also stresses the knee (hyperextension).
The classic approximation: stand next to the bike, saddle at hip bone height. Better approximation: sit on the saddle, heel on pedal at bottom of stroke, leg straight but not locked. When you clip in, the ball of the foot positions the foot, creating a slight bend at full extension.
Measurement-based method: inseam length × 0.883 = saddle height (center of bottom bracket to top of saddle). This gets you close enough to refine by feel.
Saddle setback (fore/aft position) affects knee tracking. The convention: when the crank arm is horizontal (3 o’clock position), a plumb line from the kneecap should fall over the pedal spindle. This is KOPS (knee over pedal spindle) — a starting point, not a law.
Setback interacts with reach. Moving the saddle forward effectively shortens reach to the handlebars; moving it back lengthens reach. Adjusting saddle setback may require compensating stem length change.
Saddle angle should typically be level or very slightly nose-down. Excessive nose-down slides the rider forward, putting weight on hands. Excessive nose-up creates soft tissue pressure. Start level; adjust minimally if discomfort persists.
Reach and stack describe handlebar position relative to the saddle.
Reach is horizontal distance from saddle to handlebars. Too short cramps the rider, particularly the hip angle at the top of the pedal stroke. Too long stretches the back and puts weight on the hands.
Test: riding on the hoods, you should be able to look down and see the front hub obscured by the handlebar. Hub clearly visible = too stretched; hub far behind bar = too compact. This heuristic varies by riding style — race positions are longer, comfort positions are shorter.
Stack is vertical distance. Higher stack means more upright position — less aerodynamic but less strain on back and neck. Lower stack means more aggressive position — faster but demanding on flexibility.
Flexibility limits how low you can go. A stiff rider forcing an aggressive position will round the back and stress the lumbar spine. Work within your current flexibility; it’s more easily changed than fit.
Pedal and cleat position affects knee tracking and power transfer.
Cleat fore/aft: The ball of the foot should sit over or slightly behind the pedal spindle. Too far forward stresses the Achilles; too far back loses power.
Cleat rotation: The foot should point naturally. Forcing the foot straight when it wants to angle causes knee torsion. Look at your walking footprint for natural angle; set cleats to match.
Float: Most clipless pedals allow some rotational movement before unclipping. Riders with knee issues often need more float; riders who want locked-in feel prefer less. If your knees hurt, try more float.
Q-factor (stance width) is fixed by the crankset but can be adjusted with spacers or pedal axle length. Wider stance helps riders with wide hips; narrower suits narrower builds.
Professional fit versus self-fit:
A professional fit costs $150-400, takes 1-3 hours, and uses measurement tools and video analysis. The fitter observes you pedaling, measures joint angles, and adjusts iteratively. Worth it for new bikes, persistent pain, or serious training.
Self-fitting works for adjustments on a known-good baseline. Change one variable at a time. Ride for at least an hour before evaluating. Keep notes on what you changed and how it felt. Small changes only — 5mm at most per adjustment.
Fitting is ongoing. Bodies change (flexibility, strength, weight, injury). Position that fit five years ago may not fit now. Revisit periodically or whenever pain appears.
The fitted bike disappears. You don’t notice the saddle or the reach; you notice the road, the effort, the ride. Pain-free miles compound — what hurt at 50 miles now persists to 100. The investment in fit pays dividends on every ride thereafter.
Go Deeper
Books
- Bike Fit by Phil Burt — The British Cycling and Team Sky fitter’s comprehensive treatment.
- Andy Pruitt’s Complete Medical Guide for Cyclists — Injury prevention through fit.
Tools
- Goniometer apps for joint angle measurement
- Plumb line for knee-over-pedal check
- Trainer or rollers for stationary adjustment testing
Services
- Retül, GURU, or similar motion capture systems — High-end professional fitting
- Local bike shops with trained fitters
Related: bikes, bikepacking, maintenance