Incomplete rotor sweep - cause?

[D60]

I should know this, but I don't.....so maybe I'll learn my one thing for the day.

These are front rotors removed a KL Cherokee with about 130k miles (although unk if OEM). This was the V6 with the "larger" dual piston calipers, if it matters.

The inner surface on both sides had an incomplete sweep, but both inner pads still had about 1.5 to 2.5mm friction material:

Outer faces appear normal:

The owner (a friend) did report symptoms similar to warped rotors, although I never drove it personally.

 

[CharBaby]

The inside of the rotors look as though there was too much lube packed inside of the slider cavity causing the brake pads not to fully seat flush to the rotor.. This sometimes causes pushback. I'm surprised the outsides are as smooth as they are.

 

[StarCaller]

too much lube packed inside of the slider cavity causing the brake pads not to fully seat flush to the rotor

hmm, never thought about that /

 

[Mechanician]

I've seen this on cars in the Great White North.
Brakes there need to be "serviced" regularly, to ensure the pads slide easily in their brackets.
Otherwise they can wear unevenly, and the salt will really do a number on the rotors.

 

[Mechanician]

When the brackets rust, the dimensions change, and the pads bind.
Remove the brackets, and any rattle clips on them, and clean any rust from the area indicated to bare metal.
Coat the area with a brake grease, to slow future corrosion.
An ounce of prevention sort of thing.

 

[D60]

Looking at the old inner pads I find the wear pattern puzzling

 

[ARCOgraphite]

It the pad is contacting in the center area only the center will be worn, no?
What's the profile on the rotors look like? - were they cut below the service limit?

 

[Tman220]

It's possible the pads are binding as Mechanician mentioned. Although this condition does happen frequently in rust belt states with vehicles are parked outside and and not driven every day to clean up the surface rust on the rotors. After a while the rust gets abrasive enough that it wears the pads down without cleaning up the rotors and then it's down hill from there. This rust creep is possible even with a perfectly working brake system.

 

[zfasts03]

rust intrusion

 

[Mechanician]

A clue would be how easy the pads were to remove from the holders, during disassembly. I have had many where a hammer was required to get them loose.
Remember once they do start to bind they will stick in both directions. Coming in late, and not totally backing off after the pedal is released. There's no telling what the results will look like.
It's not uncommon to see excessive force required to rotate a wheel, when off the ground. Your fuel mileage can sometimes suffer as well.

 

[99Saturn]

I had posted this a few years back:

Brake Rotors - what causes this?

Finally got around to taking off my snow tires and took a look at my rotors and saw the below. What causes this? Rotors are about 2 years old, 6,000 miles.

bobistheoilguy.com

For me it was poorly lubricated/clean slide pins.