Specialized · Tarmac SL8 · 2025 · 54

Position checks

• Knee extension147°✓ Optimal

  At the bottom of the stroke, the leg keeps a slight bend.

• Knee / pedal spindle0 mm✓ Optimal

  With the crank horizontal, the knee sits over the pedal spindle.

• Back angle40° (target 40°)✓ Optimal

  Your torso is tilted as expected for this type of bike.

• Shoulder angle83°✓ Optimal

  Your arms support your torso without locking out.

• Hip opening61°✓ Optimal

  At the top of the stroke, the hip stays open enough.

Position dimensions

Saddle height

711 mm

Saddle nose → bar

522 mm

Saddle-to-bar drop

68 mm lower

Effective reach (at the bar)

466 mm

Effective stack (at the bar)

616 mm

Hand reach

571 mm

Cranks

Recommended: 167.5–170 mm. Base: inseam × 0.21, rounded to the nearest 2.5 mm (here 170 mm). Spinning: -2.5 mm; pushing: +2.5 mm; limited mobility: -2.5 mm. If in doubt, pick the low end of the range and confirm on the road.

Target stack / reach worked out for a 100 mm stem at -6° with 20 mm of spacers.