Hello- I have a 2002 sc430 with 120000 miles, great car no problems just maintenance. For the last couple of days I heard a chirping sound as I slowed down to a stop. The only thing I could think was the brakes, but I just changed the front and rear pads March 2011. So today I looked at the front brakes and saw the pads at about 50% and everything else looked good. Then went to the rear and saw something I thought was odd...take a look at the picture and please let me know if I should be concerned. The last time I changed the pads I don't recall having this problem. If you see the red arrow you can see one of the pads is worn almost completely down and the circle shows a lip on both pads??? I checked the caliper pistons and they work fine, the pin that hold the pads is not bent and the clips are fine. Any thoughts?
Thanks

 

To me, it looks like the pads were installed incorrectly. I can't be sure given the photo, but that does not look right. It also looks like the caliper may be sticking or the slides are not lubricated properly. Depending on which side of the caliper the pads are installed.

 

I think the idea that the caliper is sticking is spot on! But, I think it is sticking for a different reason than lubrication. Brake fluid is hydroscopic, meaning it absorbs moisture. Typically, the brake fluid reservoir is full when the car is new and there is a floating rubber part of the reservoir cap which prevents an air pocket from forming at the top of the reservoir. As the brake shoes are worn down, it takes more brake fluid to fill the caliper cylinders. As the brake fluid level drops, an air space forms between the brake fluid level and the lid. The air to fill this space is drawn from the atmosphere and has water molecules in it. These water molecules are absorbed into the brake fluid and eventually form water drops. Brake fluid can absorb up to 5% water. These drops settle to the lowest and most remote regions of the brake system because they are heavier than the brake fluid.. In this case, the water drops made it to the rear wheel brake caliper cylinders, causing the cylinders on one side of the caliper to rust causing the piston to sieze in the cylinder.This effect can be minimized by flushing the old brake fluid about every 4 years. With one piston not moving, when you push the brake on, only the piston on the worn brake pad side of the caliper still works, so that is the side doing the braking and the wearing of the brake pad. This can also cause the brake to be "grabby". Not uncommon for a car of that age. You will need to replace or rebuild the calipers.

 

that's the correct answer! Caliper is sticking!

 

That back pad isn't releasing properly. Also, check the condition of the rotor - probably been getting pretty hot from that back pad. Agree that one of the pistons could be sticking due to corrosion or a sticky fluid mess. Might be time for a remanufactured caliper (about 70 bucks without pads, core exchange). However, that wear pattern looks like you may have a monster rust ring on one edge of the rotor, and/or something wasn't installed correctly. Might be time for new rotors. When you jacked up the car did you give the wheel a spin to see if the caliper was dragging? Dirty fluid, corroded pistons, etc can cause one or both pistons to hang just enough.