An apparatus for mounting a wheel and tire assembly on the drive shaft or spindle of a wheel balancer or the like in driven engagement with and concentric to the axis of the shaft. The apparatus includes a tubular adapter for receiving a double faced, stepped cone wheel centering device with a plurality of pairs of slots extending from each side past the midpoint of the device to define a plurality of evenly spaced resilient fingers on each face of the stepped cone, which fingers are bent radially outward of the adjacent portion of the cone to more effectively center the wheel by engaging the machined center hole of the wheel. The wheel is centered on and is secured to the tubular flanged adapter with the aid of the stepped cone centering device, a protective collar and a wing nut. The apparatus also includes in its combination a collet-type locking device for frictionally locking the flanged adapter in driven engagement on a smooth surfaced shaft after sliding the adapter to any desired axial position on the shaft and tightening the locking device by hand without the aid of tools. The locking device may be formed on the wing nut, or may be formed on either end of the flanged adapter.