Brake pads can wear unevenly for several reasons. I will be referring to the top of the pad as the area closest to the bridge bolt of the caliper. If top is wearing more than the bottom, the brake pressure might be too high causing the caliper to spread apart at it’s weakest point which is the unsupported bottom.
If it’s one side of pad, it will wear more on the side where the rotor enters the caliper than where it exits. As the pads contact the spinning rotor, the forces try to push the pads in the same direction. Since the pads are retained in the caliper, it causes the pads to bite harder on entry and less on exit. The B5002 / B5004 calipers are designed to offset this tendency by decreasing piston diameter on entry, lowering the pressure applied to that area. While this reduces pad taper, it also reduces overall pressure on the pad. If that becomes an issue, we also have B1900 calipers that have same size pistons and stiff billet bodies that can apply higher pressures while ensuring the calipers will not spread.
If the inner pad is wearing more than the outer, and only slightly, this is normal as the brake line enters the caliper on the inboard side and pressure rises slightly quicker. If it’s more apparent, the caliper might need to be rebuilt. If front and rear pads are wearing at different rates, check line pressures as the system proportioning might be incorrect.