Original wheels for the Twin Cam are particularly special pin drive wheels (shared with some Jaguar models of the same period). These are steel wheels with knock off center mounts, but they do not have splines. Where the wheel appears to have four lug nuts it actually has short studs with cylindrical protrusion and a conical point on the back side. These "pins" engage holes in the axle hub for positive drive. Incidentally that nice "Dunlop" logo is not original factory issue, but is a common aftermarket accessory.

The Dunlop peg drive steel wheel used on the MGA Twin Cam and "Deluxe" model cars has four taper nose pegs with cylindrical shanks to locate and center and drive the wheel. Even though there is a quick change center knock-off nut, the center hub is very short, only 1-5/8 inches long, so it is not intended to either center or align the wheel. The K/O nut will only hold the wheel firmly against the flat backing plate, and serves as the self-tightening nut (bearing against the outboard male cone surface on the wheel hub).

The outboard male cone surface on the pin drive wheel has a different included angle for the cone interface, so the knock-off nuts are unique to this application, absolutely not interchangeable with wire wheel K/O nuts.

While there appears to be an inboard tapered cone surface, it should be noted that these wheels are not hub-centric. That is, the wheel is not piloted on the center bore or on that cone surface. Those surfaces do not touch in assembly. The wheel is centered by the drive pins where they engage holes in the axle hub. This is similar to the way bolt-on wheels are mounted, secured against a flat face surface and centered and driven by the studs.

There are two slightly different versions of the Twin Cam rear hubs, but they are interchangeable and serve exactly the same purpose in exactly the same manner. The drive axle runs concentric in a large ball bearing, and the wheel pegs engage four holes in the axle hub to also be running concentric, without touching the center bore of the wheel.

Photos below compliments of Christopher Cox, The shorter hub is front Twin Cam peg drive, while the longer hub is front MGC spline drive for wire wheels (same as MGA except for the thread pitch). Since the peg drive wheel is driven and centered by the pegs, and held in plane against the flat face surface of the hub, the outboard cone is only clamping and providing the self tigtening function.