I was talking above about delaminating brake linings. Those of us with less experience may be wondering what I'm talking about so thought I'd post some pictures after doing Becky's rear brake shoes today.
Back when I worked on the shop floor brake linings were riveted, like these old ones from my "might be useful at some time" drawer:
They look like Mini rears to me? anyone? Small copper rivets which were peened over behind the metal shoe held the lining to the metal shoe. You could even buy just the linings and a bag of rivets, strip the old linings from the metal shoes and fit the new ones yourself at a considerable saving over buying exchange shoes.
Then "they" came out with bonded linings where a special bonding agent is used to literally "glue" the lining to the metal shoe and, almost overnight, riveted shoes were done away with.
Riveted linings had their problems, if you let them wear down the rivets would score the drums and sometimes rivets would come loose and cause problems in that way but this usually wasn't dangerous. Bonded linings have a "nasty little secret" which is that sometimes, especially as they age, the bonding agent starts to fail.
Most DIY car maintainers will check the depth of lining material during a service but many don't look too closely at the lining/pad (because delamination can happen to pads too) and it can be easy to miss it. What you're looking for is any separation between the friction material and it's metal backing - the sort of thing you can see in these pictures of Becky's old linings:
And don't be fooled into thinking it's just a little localized failure of the bonding. I stuck a 25 thou feeler under that last one and look at how the bonding has failed:
I didn't have to lever it up, it was just lying there. There's almost no bonding left! What would have most likely happened at some time is that one of us - Mrs J or me - would have braked a bit harder than usual and the lining would have detached from the metal shoe and followed the drum round until it wedged itself between the drum and the shoe stop or maybe the other shoe and jammed the drum solid so the wheel would have stopped rotating - That could be "fun" depending on speed and situation!
So, when you're checking your pads and shoes, look very carefully for any sign of the bonding beginning to fail and if you spot even the slightest of cracks then renew the shoe/pad immediately.
I'm actually slightly embarrassed to be showing you these pics because these linings/shoes should have been changed long before they got to this stage. I'm thinking back to how I can have missed this problem and I realize that it's actually been nearly 2 years since I checked them. Why? because Kenny's "merry men" sorted out a brake pipe problem for me around the turn of the year (oxy-acetylene heat needed) and they then, very kindly put my new wheel cylinders on when the built it back together. I remember being told they'd kept the old shoes to save me money on the job and I guess they hadn't looked too closely at them? No excuse though Jock, you must keep on top of this stuff! Ah well, all done now, just need to remember the hand brake's not going to hold all that well until the new linings bed down. Often a silver lining - pun intended - and today that was that the adjusters were easily freed off and are working perfectly!