8 Notch External Bottom Bracket Wrench

Eight-notch external bottom brackets predate the 16-notch convention that dominates current Shimano and SRAM. They live on older Dura-Ace and XTR groupsets, on most ISIS-drive cartridges, and on a handful of crossover BBs from the mid-2000s era. The notch pattern is enough different from current 16-notch that a 16-notch wrench won't fit; the 1608/2BI-US is the dedicated tool for the older interface.

For a workshop that services older bikes regularly, the 1608/2BI-US is one of those tools that lives quietly on the wall until the right BB comes through; then it's the only wrench that takes the cup off cleanly.

How it's used

Mount the wrench's notched cup over the BB's outer face so the eight machined notches mesh fully with the cup's pattern. Partial engagement is the common cause of skipping; press the wrench in until you feel the notches seat home before applying any rotation.

Drive side is right-hand thread (loosens counter-clockwise) on most older Shimano BBs. Non-drive side is normally threaded. The 350 mm handle gives the leverage to break a stuck cup without a cheater bar in most cases. Apply force slowly; jerking torque is what cams the wrench out and rounds the notches.

Compatibility

• Older Shimano Dura-Ace, XTR, and other 8-notch external BBs
• Most ISIS-drive cartridge BBs (Truvativ Howitzer, Race Face X-Type ISIS, FSA ISIS-drive)
• 8-notch 44 mm OD external cups (the era's standard size)
• Not compatible with 16-notch external BBs (current Shimano Hollowtech II, SRAM GXP / DUB, FSA Mega Exo); for those, use the 16 Notch External Bottom Bracket Wrench (1609/2BI-US).

Specs

• Material: premium flex plus carbon steel, hardened and tempered
• Surface finish: chrome-plated to ISO 1456:2009
• Handle length: 350 mm
• Notch pattern: 8-notch external, sized to the older Shimano / ISIS 44 mm OD interface

Built in Zreče

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. The 1608/2BI-US is hardened-and-tempered tool steel; the notches hold their geometry over hundreds of cup engagements without rounding the way pressed-steel value-tier tools do after a couple of seasons.

Pro tip from our mechanics

Older BBs that have been in the frame for years often refuse to release on the first try. Before applying maximum force, tap the wrench gently with a soft mallet to make sure the notches are fully seated, then apply leverage in steady pressure rather than an impact pull. A clean engagement releases what a forced one would round.

For the BB removal procedure including thread-direction reminders for the era when both threaded shells dominated: Replace or clean your bottom bracket →.