Glossary
Core fitting terms used across brand and model pages. Pair these with the twin finder when you already know numbers that fit.
Stack
Vertical distance from the bottom bracket center to the top of the head tube. Higher stack generally means a more upright cockpit for the same stem.
Reach
Horizontal distance from the bottom bracket center to the top of the head tube. Longer reach stretches the cockpit; shorter reach feels more compact.
Head tube angle (HTA)
Angle of the head tube relative to horizontal. Steeper angles feel quicker to steer; slacker angles add stability at speed (especially on MTB).
Seat tube angle (STA)
Angle of the seat tube. Steeper STAs put the rider farther forward over the pedals — common on modern race and gravel bikes.
Chainstay length
Distance from bottom bracket to rear axle. Shorter chainstays feel snappier; longer ones often track more calmly with loaded bags or big tires.