Crowfoot Open-End Wrench

A Crowfoot wrench is an open-end wrench head with no handle of its own. The 1/2-inch square drive socket on the back of the head accepts a 1/2-drive torque wrench, which lets you deliver a calibrated torque to a fastener that a normal combination wrench couldn’t reach because of the surrounding geometry.

The 1725/2CF is sized for 32 mm and 36 mm flats. The specific bike-shop application: torquing chainring lockrings on e-bike motors that use proprietary patterns; Shimano STEPS (the 1724.SSL family) and Bosch Performance Gen 2 systems (the 1723.SDM tool).

What it does

The Crowfoot’s job is geometric. Some fasteners; including e-bike chainring lockrings; sit inside the motor case, with the case wall blocking the path that a normal wrench handle would take. A Crowfoot head fits into the available access slot, and the torque-wrench handle reaches the head from outside the motor.

The 1/2-drive socket on the back of the Crowfoot accepts any 1/2-drive torque wrench. Set the torque wrench to the lockring’s spec, position the Crowfoot on the lockring flats, and torque to the click. The torque the wrench delivers is read through the Crowfoot to the fastener.

Where it earns its space in the bike shop

• Shimano STEPS chainring lockring service. Fits the flats on the Shimano STEPS chainring tool 1724.SSL. The torque spec for the lockring needs the calibrated wrench, and the Crowfoot is the head that makes the torque wrench reach the lockring.
• Bosch Gen 2 chainring lockring. Fits the Bosch Gen 2 chainring tool 1723.SDM. Same logic.
• Other proprietary lockring patterns that share the 32 mm or 36 mm flat size.

For non-e-bike work, the Crowfoot is rarely the right tool; a normal combination wrench reaches the fastener directly and saves a step. The Crowfoot earns its space specifically when the geometry blocks a normal wrench.

Why a torque wrench is essential here

E-bike chainring lockrings often have specific torque specs published by the motor manufacturer. Over-torque can damage the motor case threads; under-torque lets the lockring back out under load. The Crowfoot-on-torque-wrench combination is what delivers the spec correctly; without it, you’re estimating, and the cost of estimating wrong on an e-bike motor is high.

Specs

• Flat sizes: 32 mm and 36 mm (one tool, two flats)
• Drive: 1/2-inch square drive socket (back of head)
• Compatibility: Shimano STEPS 1724.SSL, Bosch Gen 2 1723.SDM
• Construction: forged, hardened, and tempered

Made in Slovenia, since 1919

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. The Crowfoot is a niche tool; the specific use case is e-bike chainring lockring service, and the niche exists because e-bike motor design constrains the tooling access. We built it because the install-base of Shimano STEPS and Bosch Performance e-bikes is now large enough that a bike shop needs the right tool for the job, and the dedicated lockring tools (1724.SSL, 1723.SDM) need a calibrated torque wrench delivery.

Pro tip from our mechanics

If your shop services e-bikes, this is the tool that turns “we’ll do it by feel” into “we’ll do it to spec.” For the framework on combination wrench types and when a Crowfoot is the right call: Combination wrenches in the bike shop →.