Unior Professional Chain Wear Indicator, #1643/4.

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