I had a look at the rear brakes on my partner's 2015 i30 diesel as she was complaining about a noise when braking, although when I took it out it was there all the time. I found the pads were stuck in place due to corrosion, so I took the calipers off, tapped the pads out, cleaned all the rust and scale off, and popped them back in with a smear of copper grease on the pad ears.
I noticed that the anti-rotation notches on both caliper pistons didn't line up with the pip on the back of the brake pad. so I can only assume that whoever had last changed the pads hadn't bothered to align the piston first, or somehow the piston had rotated and the pip had jumped out of the notch, allowing the piston to spin. Anyhow, I aligned the pistons properly, refitted the calipers, and the braking works fine now, with no odd noises, and the handbrake is working better.
The lessons to take away are:
1. Replace the shims that the pads slide in if they're badly corroded. Many aftermarket pad sets don't include the shims so the originals tend to get left in after their useful life.
2. Make sure the notch in the caliper is aligned to slide over the pip in the pad before re-fitting the caliper. Try and press the piston against the back of the pad so you can feel the notch slide over the pip. It's very hard to see if the face of the piston is flat against the back of the pad, you have to do it by feel.
3. Once the caliper is in position, pump the brake pedal to advance the caliper piston out to make contact with the pads. Do this BEFORE trying the handbrake, otherwise there's a risk of rotating the piston out of alignment if the notch in the piston isn't fully seated over the pip in the pad.
