Adjustable Cup Wrench

Cup-and-cone bottom brackets predate cartridge BBs by decades, and they're still on more bikes in service than the spec sheets suggest; older steel road bikes, city bikes, and rebuilt vintage frames almost all use them. The adjustable cup is the non-drive-side cup whose threading sets the bearing preload; on a well-set-up cup-and-cone BB, the cup's bearing pre-load is the single setting that determines whether the BB spins freely without play or grinds with side-load.

The 1672/2 is the wrench that turns that adjustable cup. It's a flat-stock laser-cut tool with two engagement profiles on the same body: a pin spanner on one end for adjustable cups with two-hole engagement, and a flat-jaw wrench on the other end for cups with 16.5 × 31 mm flat bosses. One wrench covers both engagement patterns; on most vintage rebuilds, both end up in service on the same bench.

How it's used

For pin-spanner engagement: align the two pins with the cup's recessed holes (typical pin centre-distance is 27.3 mm; the wrench is sized to this). Hand-load the wrench against the cup's resistance; the goal is to set preload, not to crank torque. The bearing should spin freely with no axial play; a quarter-turn at a time is the right increment.

For flat-jaw engagement: seat the jaw across the 16.5 × 31 mm boss on the adjustable cup. Same preload-setting goal, same quarter-turn pace.

The adjustable cup locknut on the same side is a separate threaded ring; once preload is set, tighten the locknut against the cup to fix the setting. The 1672/2 doesn't engage the locknut; a separate lockring wrench handles that.

Compatibility

• Adjustable cups with two-hole pin engagement at 27.3 mm centre distance
• Adjustable cups with 16.5 × 31 mm flat bosses
• Not for cartridge BBs (use the BB-specific socket or wrench instead) or external BBs (use the 16-notch wrench)

Specs

• Material: premium flex plus carbon steel, hardened and tempered
• Thickness: 2.5 mm
• Length: 204 mm
• Pin spanner: 27.3 mm centre distance between pins
• Flat-jaw wrench: 16.5 × 31 mm fitting
• Surface finish: trivalent chrome plated per ISO 1456:2009

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 1672/2 is a vintage-service tool that earned its place in the modern catalog because the bikes that use cup-and-cone BBs are still on the road, still in shops for service, and still need the right wrench. Forged-and-machined construction at 2.5 mm stock thickness gives the wrench the leverage to set preload cleanly without flexing under the hand-load that bearing preload wants.

Pro tip from our mechanics

Cup-and-cone preload is set by feel, not by torque value. The right call is “spins freely with no detectable axial play when you push and pull on the crank arm.” If the BB drags when you spin the cranks by hand, the preload is too tight; if you can feel knock when you push laterally on the crank arm, it's too loose. A quarter-turn of the adjustable cup at a time, with the locknut backed off, dials in the setting; tighten the locknut against the cup to fix it.

For the install / clean / replace decision tree across BB families: Replace or clean your bottom bracket →.