16 Notch External Bottom Bracket Wrench

The 1609/2BI-US is called a bottom bracket wrench, but on most workshop benches it earns its hook for three jobs, not one. Multi-tasking is good.

First job: install and remove 16-notch external bottom brackets. That's the dominant pattern across Shimano (Hollowtech II), SRAM (GXP and DUB), Campagnolo, FSA, Chris King, Race Face Cinch, and most other current external-bearing BBs. The cup is machined to close tolerances so the splines mesh fully with the BB's outer notches without marring the BB's finish, and the offset handle is distanced just far enough so your knuckles clear the frame but not so far as to create unnecessary cam-out, causing the tool to slip.

Second job: external Centerlock disc-rotor lockrings. The same 16-notch interface that secures HT2 BB cups is what Shimano uses for the larger Centerlock lockring on 15 mm and 20 mm thru-axle hubs. One wrench, two services.

Third job: a small wrench machined into the 1609/2BI-US's body for the preload caps on Shimano Hollowtech II cranksets. It's the cap that sets the bearing preload after the crank is reinstalled; an everyday turn that needs an everyday tool, kept on the same body as the BB wrench so it doesn't get lost. A strong magnet on the back face keeps the small wrench attached when not in use.

How it's used

For BB cups: mount the wrench's notched cup over the BB's outer face so all 16 notches mesh fully. Drive side is reverse threaded on Shimano-pattern BBs (loosens clockwise); non-drive side is normally threaded. Apply force slowly; jerking torque cams the wrench out.

For Centerlock lockrings on thru-axle hubs: same notched interface, same wrench, smaller load.

For Shimano HT2 preload caps: detach the small wrench from the magnetic back face and hand-turn the cap to set bearing preload (finger-tight plus a quarter turn, about 0.5–0.7 Nm).

Compatibility

• Shimano Hollowtech II road and MTB
• SRAM GXP and DUB external BBs
• Campagnolo road, FSA Mega Exo, Chris King, Race Face Cinch, and other 16-notch external BBs
• External Centerlock disc-rotor lockrings (15 mm and 20 mm thru-axle hubs)
• Shimano HT2 preload caps

Specs

• Material: premium flex plus carbon steel, hardened and tempered
• Surface finish: chrome-plated to ISO 1456:2009
• Handle length: ~250 mm
• Notch pattern: 16-notch external (Shimano / SRAM / FSA / Campagnolo standard)
• Includes: integrated preload-cap wrench held to the body with a strong magnet

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 1609/2BI-US's offset handle geometry is the design call that separates a workshop wrench from a value-tier tool; the offset clears modern frames' chainstays and BB shells while keeping the handle close enough to the cup to load the wrench cleanly without cam-out.

Pro tip from our mechanics

The most common BB-wrench failure mode isn't tool wear; it's incomplete engagement on the cup. Press the wrench fully home before applying torque. If the splines are sitting partially proud of the BB's notches, the first hard turn will skip and round both the cup notches and the wrench splines. Two seconds of careful seating saves a marred BB cup and a sharp scratch on someone's frame.

For the full BB removal procedure including thread direction by side and reinstall torque: Replace or clean your bottom bracket →.