The Shimano Ultegra FC-08 brings proven Hollowtech II engineering and Hollowglide chainring technology to a 46-36T semi-compact configuration — a versatile gear range that balances climbing ease with road-speed efficiency. At 165mm, these crank arms suit riders who prefer a shorter stroke for improved comfort, biomechanical fit, or triathlon positioning, without sacrificing the power transfer and shifting precision Ultegra is known for.

Highlights

• Hollowtech II outboard bearing system: positions bearings outside the bottom bracket shell for a wider stance, improved stiffness, and lower rotational mass.
• Hollow-forged aluminium crank arms: material is removed where it isn't needed, reducing weight while maintaining the torsional rigidity required for efficient power transfer.
• Hollowglide outer chainring: tooth geometry guides the chain smoothly onto and off the ring, even under load, for reliable front shifts in all conditions.
• Hyperglide+ inner chainring: synchronises the chain to a favourable tooth-chain phase during shifts, making front changes quick and quiet across the full cadence range.
• 46-36T semi-compact ratio: a flexible gear range suited to road riding, sportives, and endurance events — more top-end than a compact, more climbing range than a standard.
• 165mm crank arm length: ideal for shorter riders, triathletes, or riders with biomechanical preference for a shorter stroke.
• 110mm asymmetric 4-bolt BCD: compatible with a wide range of aftermarket chainrings designed for the Shimano road standard.

Hollowtech II Construction

Shimano's Hollowtech II system positions the bottom bracket bearings outside the shell, extending the effective bearing stance for improved stiffness and reduced flex under power. The hollow-forged crank arms remove material where it isn't needed, keeping weight low without compromising the rigidity required for efficient power transfer at the pedal.

Hollowglide & Hyperglide+ Chainrings

The FC-08 outer ring uses Hollowglide profiling — a tooth geometry shaped to guide the chain predictably onto and off the ring whether you're pushing into a climb or sprinting out of a corner. The inner ring's Hyperglide+ profile synchronises shifts to a favourable tooth-chain phase, making front changes quick and quiet across the entire cadence range. Both technologies work together to deliver the responsive, consistent front shifting that defines Shimano Ultegra performance.

Compatibility & Fit

The FC-08 is designed for 11-speed Shimano road groupsets and is compatible with all road 11-speed front derailleurs. It requires an outboard road bottom bracket (sold separately — SM-BBR60 or equivalent Hollowtech II-compatible unit). The 46-36T chainring combination pairs with an 11-speed cassette for a well-rounded road and endurance setup. Crank arm length: 165mm. BCD: 110mm asymmetric 4-bolt. Chainline: 43.5mm. Q-factor: 146mm.