🛞 Tire Compound
The rubber hardness/softness of a tire. Softer compounds grip harder but wear faster; harder compounds last longer with less grip — matched to the surface and conditions.
What it actually does
Compound is how soft the rubber is, and it is usually the single biggest grip decision you make. The right compound for the surface and temperature will out-perform any amount of suspension tuning on the wrong one.
In practice
Softer compounds grip better, warm up faster and wear out sooner; harder compounds last far longer and suit high-grip or abrasive surfaces. Manufacturers use their own naming, so a "soft" from one brand is not a "soft" from another — local knowledge at a given track is worth more than the label.
Worth knowing
Compound and tread pattern are separate choices, and both matter. The right pattern in the wrong compound is still the wrong tyre.