Aluminum Bottom Bracket Socket T47

T47 is the bottom bracket standard Chris King helped develop, adopted by Trek (T47i, internal-bearing) among others. The shell is 47 mm threaded with a 1.0 mm thread pitch; wider than BSA (33.7 mm at 1.37") which lets the cup house a 30 mm spindle without forcing the bearing inboard into the frame, where it traditionally lived in the BB30 era. The T47 cup is the answer to the ”want a 30 mm spindle without going press-fit“ question that came out of the BB30 / PF30 era.

Article 1671.T47 is a double-sided T47 socket: 16-notch on one face, 12-notch on the other, with an exchangeable guide adapter so one tool covers the T47 cup variants on Unior's chart. The 60 mm body is larger than Unior's generic 16-notch socket (52 mm); that generic 16-notch wrench will not fit these cups.

T47 thread handedness

T47 mirrors BSA's per-side thread handedness: right-hand thread on the non-drive side, left-hand thread on the drive side. The split-handedness exists to prevent the drive-side cup from backing out under pedaling load; the drive-side spindle rotates in the loosening direction relative to a right-hand thread, so the drive side is left-hand threaded to make pedaling load tighten the cup, not loosen it. Chris King helped develop the spec; Trek's T47i and the asymmetric T47a use the same handedness.

Carbon-shell T47 variants

Modern carbon frames; notably the Trek Domane SLR 9 AXS (2021+) and Trek's broader Domane / Madone T47 lineup; ship with bonded metal threaded inserts sized to T47. The bonded insert lets the T47 standard apply to a carbon frame without full-frame threading, and the BB tool doesn't distinguish between a metal-shell T47 and a carbon-shell-with-insert T47 (the engagement face is metal in both cases).

Compatibility

• T47 cups on Unior's chart: SRAM DUB T47, Wheels Manufacturing T47, Enduro T47 (OD 52.2 mm), Praxis T47 (except the GXP non-drive-side cup), and Enduro TorqueTite PF30 (OD 52.2 mm)
• Carbon frames with bonded T47 metal threaded inserts
• Not for the Praxis T47 GXP non-drive-side cup (official exclusion). T47 as a frame standard is a threaded shell; the socket also covers Enduro's TorqueTite PF30 cup where the OD is 52.2 mm

Specs

• Drive: 1/2" square drive (torque wrench, ratchet, or fixed handle). Official sheet: socket diameter 60 mm, width 34 mm, weight 106 g
• Material: CNC-machined aluminum, red-anodized
• Notch fit: 16-notch face (notch diameter 49 mm) and 12-notch face (notch diameter 46.6 mm), with exchangeable 28.8 mm and 29.8 mm guide adapters usable on both sides
• Includes: the double-sided socket and its exchangeable guide adapters; pair with the Bottom Bracket Socket Retaining Tool for low-profile cup engagement

Built in Zreče

Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The T47 socket entered the workshop tool palette when the BB standard itself moved from boutique (Chris King's original spec) to mainstream (Trek Domane, BMC Roadmachine), and the aluminum body keeps the cup face mark-free on the carbon frames where T47 lives most often.

Pro tip from our mechanics

The T47 cup wants to be checked for cleanliness more thoroughly than a BSA cup, because the wider thread diameter means a small contamination; a fleck of frame paint, a dried grease deposit; translates to a worse thread engagement than the same contamination on a narrower thread. Wipe the frame's T47 thread with a clean rag before threading the cup, and inspect the cup's leading threads for shipping debris. The five seconds spent looking is what keeps the cup square in the shell on the first quarter-turn.

For the install / torque / thread-direction reference: Replace or clean your bottom bracket →.

FAQ

What does the 1671.T47 socket do? It installs and removes T47 external bottom-bracket cups. Unior's sheet describes a double-sided socket: 16-notch on one face, 12-notch on the other, with an exchangeable guide adapter so one tool covers the T47 cup variants on the official chart. The body is CNC-machined from aluminum billet and anodized red so it does not mark aluminum cups.

Why two notch counts, and what is the adapter for? T47 cups are not one spline pattern. Official spec is a 16-notch face (notch diameter 49 mm) and a 12-notch face (notch diameter 46.6 mm). The black center pieces are exchangeable guide adapters, 28.8 mm and 29.8 mm, and Unior says they can be used on both sides. The 29.8 mm adapter is marked Ø29 on the official photo.

Which T47 cups does it fit? Unior's chart lists SRAM DUB T47, Wheels Manufacturing T47, Enduro T47 (OD 52.2 mm), Praxis T47, and Enduro TorqueTite PF30 (OD 52.2 mm). It is not compatible with the Praxis T47 GXP non-drive-side cup. Chris King 'fits most models' sits on Unior's generic 16-notch socket, not this T47 SKU.

What are the official dimensions, and what else do I need? Article 1671.T47, code 628495. Official sheet: socket diameter 60 mm, width 34 mm, 1/2 inch square drive, 16- and 12-notch faces, weight 106 g (tolerances apply). Unior lists no spare-part SKUs. For low-profile cups, pair it with the 1671.RET socket retaining tool; the 1/2 inch square takes a torque wrench, ratchet, or fixed handle.