Bike fit glossary

Every term used in our analysis results and guides, explained in one place.

Saddle adjustments

Saddle — the primary contact point; the "top of the saddle" is the reference for measuring saddle height.

Seatpost — the tube that holds the saddle; available with zero offset or with 15–25 mm of rearward offset.

Saddle height — the distance from the center of the bottom bracket to the top of the saddle, measured along the seat tube line. Adjustment number one in any bike fit.

Setback — the fore-aft position of the saddle: the horizontal distance from the saddle nose to a vertical line through the bottom bracket.

Saddle tilt — the saddle's angle relative to horizontal; a level saddle is the standard starting point.

Rails — the bars under the saddle on which it slides fore and aft.

The handlebar zone

Handlebar (drop bar) — road handlebars; width is usually measured center-to-center.

Stem — the part connecting the handlebar to the fork steerer; its length (70–130 mm, in 10 mm steps) is the main reach adjustment.

Hoods — the brake/shifter bodies where your hands rest in the standard road position.

Drops — the lower, curved part of a road handlebar.

Spacers — the rings under the stem; moving them raises or lowers the bar — the cheapest drop adjustment there is.

Aero extensions — the TT/triathlon bars your forearms rest along.

Arm pads — the forearm supports on aero extensions.

Frame geometry

Stack — the frame's height: vertical distance from the bottom bracket to the top of the head tube.

Reach (frame) — the frame's length: horizontal distance from the bottom bracket to the top of the head tube. Note: "reach" is also used for the saddle-to-bar distance of a riding position; context decides.

Head tube — the front tube in which the fork rotates.

Seat tube — the tube holding the seatpost; its angle decides how far forward the saddle sits natively.

Top tube — the upper tube; its "effective" length is the old comparison metric, superseded by stack/reach.

Bottom bracket — the crank axle; the origin of all geometry and fit measurements.

Wheelbase — the distance between wheel axles; stability.

Standover — the top tube's height above the ground; a safety criterion, not a fit criterion.

Crank / crank arm — the pedal lever; its length (typically 165–175 mm) directly influences knee angle.

Position measurements

Knee angle / knee flexion — the knee's bend angle at the bottom of the pedal stroke; the central measurement for saddle height.

Bottom dead center (BDC) — crank at the 6 o'clock position.

Torso angle / back angle — the angle of the hip–shoulder line relative to horizontal.

KOPS (knee over pedal spindle) — the historical knee-over-pedal-axle reference for setback; a starting reference, not a rule.

Reach and drop (position) — the distance, respectively the height difference, between saddle and handlebar.

Inseam — the inner leg length (floor to crotch); the basis of the classic saddle height formulas.

Cadence — pedal revolutions per minute (rpm).

Contact points and accessories

Cleats — the plates mounted on shoe soles that click into the pedals; their position influences the whole leg chain.

Clipless pedals — pedals with mechanical engagement (the historically paradoxical name refers to the absence of old-style toe clips).

Trainer (home trainer) — the stationary riding stand; the mandatory stage for analysis recordings.

Bib shorts — cycling shorts with shoulder straps.

Missing or debatable terms? Let us know — this glossary is a living document, updated together with the guides.