If you're picking between two rubber track quotes because one lists a higher Shore A hardness number, you're comparing numbers that may not even be measuring the same thing. Shore hardness is an indentation result — how much a specific durometer, pressed with a specific force and geometry, resists sinking into the material. It says nothing directly about tensile strength, tear resistance, abrasion loss, or how long the track will actually survive on the ground. A higher number doesn't mean a tougher track; it just means more resistance to that one specific indentation test, under whatever conditions produced it.
The scale itself is part of the result, and mixing them is a common trap. Shore A and Shore D use different indenters and different forces for different material ranges — "70 Shore A" and "70 Shore D" are not the same mechanical state wearing different labels, and they can't be subtracted or ranked against each other as if one common ruler produced both. Beyond the scale, rubber is viscoelastic, meaning the reading can shift depending on how long after contact it's recorded. A quote that just says "Shore A 70" with no reading time attached is missing a variable that can move the number.
Test conditions decide whether two numbers are even comparable. Specimen thickness matters, because a thin rubber layer over a rigid substrate responds differently than a standard-thickness test piece. A curved tread surface can prevent the durometer from seating the same way it would on a flat specimen. Surface condition, texture, contamination, and even where on the track the reading was taken all shift the result — a reading on a tread lug and one on an inner surface aren't necessarily measuring equivalent material. Temperature adds yet another variable, since rubber's response changes with conditioning.
This is exactly how a seemingly precise comparison falls apart. Picture one report showing 68, 69, 68 Shore A on a flat, conditioned lab specimen, and another showing 72, 66, 70 on a curved finished tread with no stated timing. Averaging those and comparing 68.3 against 69.3 looks like a clean one-point difference — but the two groups were measured on completely different objects under different conditions. That's not a material comparison; it's a coincidence dressed up as data.
Hardness also doesn't rank a track's overall durability, because wear life depends on abrasion resistance, tear resistance, adhesion between bonded layers, and fatigue behavior in the reinforced structure — none of which Shore A measures directly. This guide breaks down exactly what questions to ask a supplier before trusting a hardness number as a durability claim: When Should Track Shoes Be Replaced?
To check current stock and specs for your machine:
https://ca.aft-parts.com/collections/rubber-track
A Shore A number tells you what one test measured — not which track will outlast the other on your job site.
