I changed the brakes yesterday on my 14 FX4 and noticed the surface of the driver side caliper piston had raised dimples. Is that common? Definitely not something I have ever seen on any other vehicles, and the passenger side was as normal as would be expected.

 

There is 4 pads, two with pins and two without. I forget where the go. Inside or outside edge.

 

The pads with ears, go on the inside of each front side, if that is what is being discussed here.

 

Appears to be a flaw in the piston, just take a file and clean the bump off it will be fine.

 

That is really odd, maybe that pair missed a machining step that faces that end of the pistons? The operator might have had a couple cold ones at lunch.