Hope you are using a wind back kit like this -   When you wind back the pistons, make sure the cut outs are in line horizontally with the caliper or the caliper will need to be forced to fit over the brake pads. The photos are of a Vauxhall Corsa VXR I did last year. It had the same issue as the Avensis where the inner pad wore quickly.  piston in the wrong position.        piston in the correct position   Brake pad wore down at one end!   Just like the Avensis, there is