Out of interest, how does one measure/calculate track wear as a percentage? Is it as simple as comparing to the track depth of a new track? Or is it more complex than that? Same for steel?
There’s a few factors involved. Wear of the rails effectively causes an increase in the, for want of a better description,“rolling radius” of the chains. Wear Of the bushes will lead to a requirement to tension the tracks, on System One chains where the idler runs on the bushes (according to Cat this doesn’t happen as the bushes roll, but it can, again to a minor extent.
The biggie is internal bush/pin wear and this is measured by taking wear over usually five pins and dividing by five to compare to as-manufactured pitch. There will be a wear limit defined by the manufacturer for the particular pitch, and someone like Astrak have wear guides to refer to as well. When wear gets bad the chain loses its lateral rigidity and can walk off the idler or top rollers, usually when turning in deep mud or side-slope working. This is the bit that can be measured objectively whereas rail profile is a bit more subjective.
On the rail part of the chain there are three wear zones per link. The middle of the rail where it pulls around the sprocket, eventually leading to a collapsing, and the area above the link/pin either end which wears minutely as the chain breaks over the top rollers. On a badly worn chain there will be three areas of scalloping which can be seen with a straight edge, and sometimes without, and the ride is much rougher.
Hope this helps a bit.