Chainring Truing Wrench

A 243 mm forged-steel chainring truing tool with two notch sizes machined into the working head; the smaller notch for aligning individual chainring teeth, the larger notch for working on the chainring body. The leverage of a 243 mm handle is what brings a bent ring back to flat without flexing the crank spider or stressing the chainring bolts.

A bent chainring is one of the more common drivetrain-rideability issues that customers describe as “the chain skips” or “shifting feels weird.” A chainring tooth that's bent half a millimeter off the ring's plane lifts the chain at that tooth on every revolution, which the shifter reads as a mis-shift and the rider feels as a skip. Straightening the tooth restores the chainring's working geometry without replacing the ring.

How the two notches work

• Smaller notch: sized for a single chainring tooth. Slide the tooth into the notch and apply lateral force to bend the tooth back to plane. The notch's narrow span concentrates the force on the bent tooth without affecting the neighboring teeth.
• Larger notch: sized for the chainring body (the structural ring behind the teeth). For a chainring that's bent across multiple teeth at once, the larger notch lets you work on the ring's structural plane rather than tooth-by-tooth.

The 243 mm tool length is the leverage choice. Long enough to bring a stubbornly-bent ring back to flat without the mechanic having to fight the tool; short enough to fit in a workbench-tray drawer without dominating the workshop.

Compatibility

• Chainring teeth: any standard chainring with steel or aluminum teeth (carbon-toothed chainrings are not candidates for truing; replace, don't bend)
• Chainring body: aluminum and steel rings; some titanium rings; SRAM AXS Eagle chainrings (the four-arm direct-mount design)
• Not for: carbon-fiber rings, oval (Q-ring) profiles where the tooth pattern is non-circular, integrated chainring/spider assemblies where bending one tooth stresses the spider

Specs

• Length: 243 mm
• Notches: small (single tooth) + large (chainring body)
• Material: forged steel head with padded handle
• SKU: 1667/2 (619704)

Built in Zreče, Slovenia

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. The 1667 chainring truing wrench is the drivetrain-truing complement to Unior's wheel-truing fork (1689.2) and disc-brake rotor truing fork (1666 series); same forged-steel construction approach, sized for the specific component the tool works on.

Pro tip from our mechanics

Most bent chainrings happen from a chain drop that wedges between the chainring and the chainstay, or from a crash where the chainring bears load against a rock or curb. Before truing, check whether the chainring bolts are still snug; a loose bolt at the chainring-spider interface can mimic a bent chainring on the shop floor, and tightening the bolt may fix the symptom without needing the truing tool at all.

For the broader picture on drivetrain service, including chainring inspection alongside chain replacement: How to clean and lubricate your chain; and what we use →.