I thought that maybe I was doing something wrong and my MX-5 requires more skill and/or knowledge than the Austin Metro and the Toyota Starlet SR that I used to own.
Since the pads still had life left in them, after some months I asked the help of a friend who has experience with high-performance cars too.
He came to the same conclusion; the pads where too wide. Has anybody used this pads on a stock MX-5 Mk3 (2007)? Do they just drop in?
The only problem I have had with brake pad metal backings are the wings that slide on the caliper carrier bracket usually between a spring type clip / shim sometimes need to be filled down to give a reasonable “slide in” but not loose as that can cause rattling.
I have had that on my Impreza front and rears 09 car, a good few Mk1, Mk2 and Mk3 MX5 rears but not either the main body of the backing plate is too wide or the extreme edges of the wings are too wide.
Sounds to me like you have been unlucky and you have been supplied with the wrong physical brake pads in possibly the correct box in error. Things like that happen now and then. I have fitted that make of pad before and I cannot remember any issues with them.
I recently fitted Ultimax 2 pads front and rear to my 2009 1.8 NC 3.5 with no problems. I used the shims off the old shoes. The front ones say on the box DP1774, Mazda MX5 2006 on. Sumitomo 5016.