There's a moment in a chain's life when the readout matters more than the binary. You want to see whether you're at 0.4% or 0.55%, not just whether the chain has crossed a threshold; you're planning the next service interval, not making a single keep-or-replace call. The Professional Chain Wear Indicator 1643/4 is the tool for that moment. It's a swing-arm dial gauge with a continuous 0 to 1.2% readout, so the chain doesn't just pass or fail; you get the actual elongation number. The mechanism is simple. Two pins drop into the chain, the swing-arm is pressed tight, and the gauge window reports the wear figure. No batteries, no calibration ritual; the indicator is set at the factory and stays set for the life of the tool. How to read it The 1643/4 reads the chain against a single replacement trigger at 0.6% stretch. That's the threshold most chain manufacturers historically cited as the universal swap point, and the gauge was designed around it; the dial gives you a continuous reading from 0 up through 1.2% so you can track wear progression over service visits. When this is the right call Modern 11-, 12-, and 13-speed chains tighten the spec. Current chain-maker guidance is to swap a narrow-spaced chain at or before 0.5%, where the 1643/4's gauge triggers replacement slightly later (0.6%). On those drivetrains, the Chain Wear Indicator 1644/6 reads both 0.5% and 0.75% directly on the tool body and is the more accurate pick. The 1643/4 stays useful where a continuous reading matters more than a tighter threshold: 6- through 10-speed drivetrains, shop benches that service mixed-fleet bikes, mechanics who want to log wear progression across service visits rather than just confirm a swap moment. It's the gauge for “how worn is this chain right now,” not the gauge for “should I replace this 12-speed today.” Specs 137 × 25.5 × 20 mm 142 g Swing-arm dial gauge, 0 to 1.2% range 0.6% replacement trigger Lifetime warranty Article number: 1643/4 Built in Zreče, Slovenia Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The 1643/4 is one of the older chain-wear tools in the catalog, and the gauge it carries reflects the chain-wear consensus of an earlier generation of drivetrains. The dial mechanism itself is still the cleanest way to read elongation as a continuous value; you can watch a chain age, not just confirm when it's gone. Pro tip from our mechanics Reading the dial is the easy part. Knowing when to act on it is where the call gets made. Our chain-replacement guide lays out what happens to the cassette teeth between 0.5% and 0.75%, why a worn chain on a new cassette is the most common drivetrain mistake, and how to plan service intervals around the gauge rather than around mileage estimates: When and how to replace your chain → FAQ How is the 1643/4 different from a drop-over chain checker? Drop-over gauges are pass/fail — the blade either seats in the chain or it doesn't at one or two fixed thresholds. The 1643/4 is a swing-arm dial gauge: set the pins in two links, press the arm tight, and the window reads elongation as a number anywhere on its 0–1.2 mm scale. That lets you track how far along a chain is, not just whether it has crossed a line. Can I use it on a modern 11-, 12-, or 13-speed chain? It reads any chain — Unior's own instruction is simply to insert the pins into two links and read the gauge. The catch is the threshold: current chain-maker guidance replaces a narrow 11-to-13-speed chain at or before 0.5% elongation, and a two-pin gauge folds roller play into its millimeter reading. For those drivetrains the Chain Wear Indicator 1644/6 reads 0.5% and 0.75% directly; the 1643/4 is at its best on 6-to-10-speed and mixed-fleet work. Does it need batteries or calibration? No. It is a purely mechanical gauge — no electronics, no battery, and no user calibration. The dial is set during manufacture; you insert the pins, press the swing arm tight, and read the wear figure in the gauge window. What are the dimensions and weight? The tool measures 137 × 25.5 × 20 mm and weighs 142 g, so it stores flat in a bench drawer or travel case. It is covered by a lifetime warranty.
