Ratchet Wrench 14mm + 15mm

Square-taper cranks haven't disappeared, and a workshop that services older road and city bikes runs through more of them than the catalog might suggest. The crank bolt on a square-taper crank is typically M8 with a 14 or 15 mm hex head (Sugino, Stronglight, TA, Shimano FC-7710-class); the same crank often pairs with a 14 mm crank-arm nut on the opposite end. Two sizes, one wrench, and the right tool keeps the install or removal moving without a tool change mid-job.

The 1621-1 in the 14 + 15 mm cut is the ratchet for that workflow. One head carries a 14 mm socket, the other carries a 15 mm socket; both at 3/8" drive, both with 75-tooth ratchet engagement. Loosen the crank bolt at one head, swap the wrench around, tighten the crank-arm nut at the other; no tool change, no fumbling for a 1/2" adapter, no shop-time lost.

How the 75-tooth ratchet helps in tight quarters

A square-taper crank bolt is recessed into the crank arm's spider; the working space for the wrench head is constrained by the chainring, the chainstay, and the frame's BB shell. Standard ratchets with coarser tooth counts (36 or 45 teeth) need a wider swing arc to engage the next tooth, which means lifting the wrench off the bolt and re-setting after every few degrees of rotation. The 75-tooth engagement on the 1621-1 needs a 4.8° arc to advance one tooth; narrow enough to ratchet the bolt without pulling the wrench off, even on the most constrained square-taper installs.

Sibling product

The Ratchet Wrench 14 mm + 8 mm covers the other common square-taper size pairing; a 14 mm socket plus an 8 mm hex driver for newer square-taper crank bolts with a recessed hex head. The two ratchets share the same body geometry and 75-tooth engagement; a shop that sees both vintage and current square-taper cranks runs both on the bench.

Compatibility

• Square-taper crank bolts with 14 or 15 mm hex heads (Sugino, Stronglight, TA, Shimano FC-7710-class)
• 14 mm crank-arm nuts on the same crank
• Other M8-class fasteners in the same size range
• Any 3/8" drive socket for general use (the sockets are interchangeable on the ratchet body)

Specs

• Drive: 3/8" square drive
• Ratchet engagement: 75 teeth (~4.8° arc per tooth)
• Head sizes: 14 mm and 15 mm sockets, integrated to the ratchet body
• Material: premium flex plus carbon steel, hardened and tempered
• Surface finish: trivalent chrome plated per ISO 1456:2009
• Includes: the dual-head ratchet itself

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 1621-1 is the kind of tool a shop's mechanic reaches for without thinking; once the crank is in front of you, the 75-tooth engagement is what makes the rest of the job feel fast.

Pro tip from our mechanics

Square-taper crank bolts torque to 35–50 Nm (Shimano publishes the band; Sugino and Stronglight historically converge at the same range), which is above the comfort range for a hand-load ratchet wrench. The 1621-1 is the right tool for breaking the bolt loose and for spinning the bolt down quickly during reinstall; the final torque is a torque-wrench job, not a hand-feel job. Spin down with the ratchet, switch to a torque wrench for the final 35–50 Nm.

For the crank removal procedure including puller selection by spindle type: How to remove a crankset →.