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 sponsors professional road and mountain-bike race 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 →.