Most operators check track sag-the amount the track droops between the carrier rollers. But measuring sag only tells you if the tension is correct; it doesn't tell you if the track pins and bushings are worn out. The only way to accurately assess undercarriage life is to measure the track pitch-the distance between the center of the pins.
Take a length of tape or a specialized "chain wear gauge." Lay it along the bottom of the track and measure the distance of 10 pins (or "pitch holes"). Compare this measurement to the brand-new specification found in the service manual. As the pins rotate inside the bushings for thousands of hours, the steel wears away, making the pins smaller and the holes oval. This causes the track chain to physically stretch.
If a 10-pitch measurement exceeds the "service limit" (usually 2-3% over new), the track is effectively worn out, regardless of how the tread shoes look. An elongated track no longer fits the sprocket teeth correctly. Instead of the tooth fitting snugly between the pins, the chain rides up on the tips of the teeth, accelerating sprocket wear. Trying to retension a pitch-elongated track only accelerates the wear on the carrier rollers and idler bearings, as the chain is physically too long to be tensioned correctly.
