The important function all the rest of those screws serve
And all the rest of the cars? Well, if you take a look at the vast majority of the rotors fitted to them, you’ll notice most have a spot in the rotor that’s countersunk. And the reason for that is it allows one itty-bitty fastener to correctly locate the brake rotor.
“But Lem! The lug nuts will center it up!” I can hear you thinking right now. And that is true in the case of the wheel. The brake disc, however, almost always pilots off the hub.
Simon Marenda, one of Dorman’s engineers who deals an awful lot with hub assemblies, educated me further. “Rotors are usually going to be hub-piloted. The lugs can have wider tolerances so the rotor will fit over them easily before having to climb over the hub flange when you’re installing them.” He then shipped me a drawing that confirmed this: there’s a step visible, plain as day.