This is regarding my son's vehicle, a 2009 Kia Sedona van. We replaced the rear brake pads and rotors about 18 months/25K km ago. He and his family are on a road trip. One rear brake started making a bad grinding noise. We've been troubleshooting together by text and phone to try to get this sorted out.
He's visiting relatives, excellent people, and has good weather and the use of tools and a good level spot to work outside. He's found, on the driver's side, that the outer brake pad has worn down to metal, and has chewed up the rotor badly. The inner brake pad still has lots of meat on it.
This seems weird to me; in my experience here in the rust belt, the usual cause of uneven pad wear is due to the caliper not sliding well on its pins. When that's the case, the inner pad wears way faster than the outer one. (This assumes that the caliper's piston(s) are on the inner side of the caliper; I've never seen otherwise.)
He's found that the caliper still moves freely on its pins, but that the brake pads are not sliding freely within the caliper housing. I believe that the inner pad (i. e. the one that the piston contacts) must move freely, but that it's not essential for the outer pad to move.
Due to this unusual wear, we're wondering whether the caliper is sticking on hydraulically - that is, is the piston not retracting properly when the brakes are not applied. I can't think of any other reason the outer pad would wear more than the inner. But wouldn't that wear both pads prematurely? What if the inner pad is binding, and the caliper is stuck? The piston would meet resistance from the stuck inner pad before the inner pad contacts the rotor, and the caliper would then move inward, pulling the outer pad into contact with the rotor.
Does this make sense? Any other theories? Many thanks in advance.
At this point, he's done a cheap pad slap to get them home safely, accepting that the pads will be sacrificial. Once they're back, and we have our driveway back again (which is presently not accessible due to our street being rebuilt), we plan to change out the calipers, rotors, and pads on both sides on the back.
He's visiting relatives, excellent people, and has good weather and the use of tools and a good level spot to work outside. He's found, on the driver's side, that the outer brake pad has worn down to metal, and has chewed up the rotor badly. The inner brake pad still has lots of meat on it.
This seems weird to me; in my experience here in the rust belt, the usual cause of uneven pad wear is due to the caliper not sliding well on its pins. When that's the case, the inner pad wears way faster than the outer one. (This assumes that the caliper's piston(s) are on the inner side of the caliper; I've never seen otherwise.)
He's found that the caliper still moves freely on its pins, but that the brake pads are not sliding freely within the caliper housing. I believe that the inner pad (i. e. the one that the piston contacts) must move freely, but that it's not essential for the outer pad to move.
Due to this unusual wear, we're wondering whether the caliper is sticking on hydraulically - that is, is the piston not retracting properly when the brakes are not applied. I can't think of any other reason the outer pad would wear more than the inner. But wouldn't that wear both pads prematurely? What if the inner pad is binding, and the caliper is stuck? The piston would meet resistance from the stuck inner pad before the inner pad contacts the rotor, and the caliper would then move inward, pulling the outer pad into contact with the rotor.
Does this make sense? Any other theories? Many thanks in advance.
At this point, he's done a cheap pad slap to get them home safely, accepting that the pads will be sacrificial. Once they're back, and we have our driveway back again (which is presently not accessible due to our street being rebuilt), we plan to change out the calipers, rotors, and pads on both sides on the back.