No question here, just a report. I replaced the brake pads on my 2002.5 Proteg5 the other day, and found to my surprise that one of the floating pins on the RR caliper was seized. For those not familiar with the way these floating calipers work, there is only one piston and it acts upon the inner pad. The entire caliper "floats" on sliding pins, though, so when that piston pushes on the inner pad, the reaction forces the caliper itself to slide the other way. A structure that wraps around to the outside of the disc applies this reaction force to the outer pad. It's a neat way to simplify a caliper -- no need for a second piston on the outside, nor plumbing to connect the hydraulics through -- but it does require that the pins allow the caliper to slide freely. There are two pins per caliper, and one pin must be removed to swing the caliper out of the way to change pads.
On my RR caliper, the removable pin came out easily and was in fine shape. But, I couldn't swing the caliper out. I thought I had forgotten to disconnect something, it just didn't wanna move. Eventually I managed to force it to swing away, but then in trying to get it to loosen up -- twisting it back and forth -- I managed to start that pin unscrewing. The hard part of the whole job was getting that seized pin to slide out (it normally should just slide apart once the caliper has been swung away from the rotor), which eventually involved fitting tools around it to wedge it and levering it apart. Once apart, it was a fairly simple matter to clean up the pin and the hole (the pin looked fine, no rust or anything, still shiny and new-looking), grease it up with brake caliper grease, and reassemble. Even the boot looked fine.
In theory, such a seized pin should affect the outer pad; the piston will still act against the inner pad just fine. One possibility is that the outer pad doesn't engage, in which case you'd expect to see less wear on that pad than the other rear pads. Another possibility is that the outer pad doesn't release, in which case you'd expect to see more wear on that pad than the other pads. However, the outer pad seemed to show about the same level of wear as the other three rear pads, as though nothing was out of the ordinary.
I'm left with no idea why it seized in the first place. It even seemed to still have some good grease in there.
On my RR caliper, the removable pin came out easily and was in fine shape. But, I couldn't swing the caliper out. I thought I had forgotten to disconnect something, it just didn't wanna move. Eventually I managed to force it to swing away, but then in trying to get it to loosen up -- twisting it back and forth -- I managed to start that pin unscrewing. The hard part of the whole job was getting that seized pin to slide out (it normally should just slide apart once the caliper has been swung away from the rotor), which eventually involved fitting tools around it to wedge it and levering it apart. Once apart, it was a fairly simple matter to clean up the pin and the hole (the pin looked fine, no rust or anything, still shiny and new-looking), grease it up with brake caliper grease, and reassemble. Even the boot looked fine.
In theory, such a seized pin should affect the outer pad; the piston will still act against the inner pad just fine. One possibility is that the outer pad doesn't engage, in which case you'd expect to see less wear on that pad than the other rear pads. Another possibility is that the outer pad doesn't release, in which case you'd expect to see more wear on that pad than the other pads. However, the outer pad seemed to show about the same level of wear as the other three rear pads, as though nothing was out of the ordinary.
I'm left with no idea why it seized in the first place. It even seemed to still have some good grease in there.
