Post
by Wayne Sheldon » Wed Jan 06, 2021 5:48 pm
John Saylor, Were the grooves caused by the lining? Or the rivets?
A problem that never seems to go away, is that rivets are often sold as "brass rivets" when they are actually brass plated steel rivets. This was happening over fifty years ago! And I ran into it again only a few months back. Back in the days when drum brake shoes would be purchased either new or relined used shoes, over fifty years ago, a lot of the companies began using steel rivets. A LOT of the steel rivets were brass plated. I used to take a pencil magnet with me to buy replacement shoes to test the rivets before I would accept them from the store. This went on for several years before the friction materials companies went to bonded (glued) linings.
Been awhile since I ran into it with model T replacement linings. However about twenty to thirty years ago, I made a stink with a couple of the model T parts suppliers about lining sets that had brass plated steel rivets included. They were not at that time aware that the rivet suppliers had changed what they provided. The problem at that time for the model T world was quickly corrected, and I haven't heard of that problem in transmission lining sets since.
I do still run into it with rivets themselves. Whether from the local Ace, or an internet hardware supplier, brass plated steel rivets are sometimes called "brass rivets".
Even so-called soft steel rivets should NEVER be used for brake linings of any type. Even if "peened" with a slow rivet press, the peening will harden the steel. If peened with a hammer, the hammering work hardens the steel, The hardening will create a cutter that will begin cutting the drum right from the start. Even IF the soft steel rivet is not hardened, the abusive environment of the brake lining (hot/cold cycling, maybe moisture present?) will cause the steel rivet to rust quickly. While the rusting is not serious enough to significantly weaken the rivet, the dust rust particles WILL flake off and embed in the surface of the lining. This, usually inline with the rivet itself. Iron oxide is a serious abrasive, used in sandpaper and grinding stones! The embedded rust particles turn the brake lining surface into a grinding surface.
Back when replacement brake shoes were being sold with steel rivets, I saw many dozens of shoes and drums cut in line with the rivets because of the abrasive effect of the iron oxide. That is a lot for someone that never had a paying job in an automotive repair business!
I have in recent years run into the same problem with modern cars and disc brakes. The shorter surface disc brake pads seem to have less tendency to cut away the disc's surface, but it is still enough to destroy good discs prematurely.
