Master Chain Tool

A worn chain quietly destroys the rest of your drivetrain. Push past the wear-indicator threshold and the elongated rollers carve your cassette teeth and round off the chainrings within a few hundred miles. The Master Chain Tool is the tool we reach for the moment a wear-checker drops in past spec, and the one we'd want on a stand at every shop that takes chains seriously.

This is the most complete chain tool in our range. The machined body and precisely-made spindle threads do the visible work; the floating chain support is the quiet detail that matters. It centers the chain plate against the driving pin on its own, so the pin pushes straight through every time. No coaxing, no off-center marks, no tweaked outer plates after reinstall.

Compatibility

The Master Chain Tool works with every derailleur chain from 6 to 13 speed. SRAM's AXS flat-top chains get their own dedicated support insert. Campagnolo 11-, 12-, and 13-speed chains are supported for peening; an included pin blocker handles the second half of the connection. For shop bikes and singlespeeds, the 1/8″ support covers those too.

Three interchangeable chain supports ship in the box: a single-link support (pre-installed), a wider double-link support for extra grip on stiff or fresh chains, and the dedicated AXS support. A hidden compartment in the body of the tool holds a replacement chain pin, which is where it'll be when you need it instead of the cassette drawer you swore it was in.

Specs

• 6–13-speed derailleur chains; SRAM AXS flat-top; Campagnolo 11/12/13 peening; 1/8″ single-speed
• Machined body, trivalent chrome plated
• 89.5 × 42 × 191.5 mm
• 560 g
• Article number: 1647/2BBI

Includes: three interchangeable chain supports (single-link pre-installed, double-link, dedicated SRAM AXS) plus a replacement chain pin in the hidden compartment.

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. Bikerumor, marking the centenary: "Unior is one of the rare companies to make their own tools in-house and has been doing so for a hundred years now in the same place in Slovenia." The Master Chain Tool is one of the products where that vertical integration shows up. The modular insert system is Unior's own design, not a re-badge of a generic chain tool body.

Pro tip from our mechanics

Most home mechanics underestimate how often a chain wears out. By the time you can hear chain skip on the cassette, the cassette is usually past saving too. Our chain-replacement guide walks through the wear-checker reading that should trigger the swap, the difference between Campagnolo peening and SRAM PowerLock reinstalls, and where the Master Chain Tool's supports earn their keep: When and how to replace your chain →