It looks like the front brake rotors are smaller than they maybe should be.



I've been driving a lot more, and I've noticed that the brakes will start to sink if I am on them for an extended period of time. is this a master cylinder or a slave?

Also, the front caliper pistons are not fully covered by the brake pad. Maybe 2/3-3/4's of it are. Is this typical or are my rotors/brake pads too small. I've done brakes many times myself, and it always seems the pad covered the piston.

 

Sinking pedal is either a fluid leak somewhere or a failing seal in the master cylinder.
Are you losing fluid?

Pad/caliper fit:

 

I think every failing master cylinder, I've noticed first while I was at a Stop light, or sign. If you are sitting there and the petal is going down, hopefully it's peeing fluid out somewhere cheap, instead of it being a bad master cylinder.

 

I experienced this a while back, both the sinking pedal and the creep at stop lights. It ended up being a bad primary piston in the master. The aluminum had actually been corroded away, probably by moisture, which allowed fluid to leak by the seals. I got the OMIX-ADA master cylinder rebuild kit ($45) which came with the springs, seals, and pistons. No more sinking pedal and no more creep.

 

autozone has a rebuild master cylinder for 25 bucks. Need to pick up an o2 sensor as well, so going to do those today, unless I should absolutely avoid the rebuild cylinder. My experience between new and rebuilt for older vehicles is that there isn't much difference.