After our local ace struggled with terrible streetbike drum brakes of the 1960s, whose linoleum lining glazed over with slippery stuff when used hard, it was great to hear him hold forth about his brand-new production racer: “It’s so cool! When you want to go faster, you just twist the throttle more. When you want to stop harder, you just pull the brake lever more. And there’s lots left!”

That was a year before, but now, cracks had appeared in that apparent perfection. Real cracks. As in the iron drum liner against which the twin leading brake shoes were pressed when you pulled that lever. After each race weekend, we pulled our front wheels and saw that a network of cracks was spreading. One rider had already reported a chunk had fallen out of his brake. Lucky it didn’t jam, locking the front wheel.

At the time, I was sure I could soon machine an alternative universe from solid billet, using the lathe, milling machine, and other tools at my place of work. I volunteered to machine away the heat-blackened, cracked drum liner and replace it with a shining, fresh ring of steel.

We had all read about the wonderful Al-Fin process, by which iron or steel parts could be “tinned” with aluminum, then placed in a mold to have aluminum cast around them, forming a perfect bond between the two metals. We were somehow sure that this was how our brake drums had been made.

I made up a mandrel to support the bare brake drum in the lathe, tire, tube, rim, and spokes having been removed. Soon I had it revolving and advanced the tool bit into the cut. Cut after cut… This took time, but finally I knew I was close to having removed all the iron. Now long strips were peeled away and the side of them that had faced the aluminum beneath was dark with heavy rust. What was this?

Finally, I had a nice smooth continuous aluminum surface, ready to receive the fresh steel liner I had prepared—with a 0.007-inch interference fit. And I realized that our much-admired production racer brakes were far from being the Al-Fin wonders we had imagined. Instead, it was clear that the makers had stockpiled the machined iron drum liners outdoors, where they had rusted thickly. Then, one by one, they had been set into casting molds without the slightest preparation, the molds were closed, and the molten aluminum was poured.

Instead of the “intimate thermal contact” between iron and aluminum claimed for the Al-Fin process, we had brake drums whose iron liners were so well insulated by rust from the surrounding aluminum that they were unable to get rid of the heat generated by braking. And so, they overheated. Given a full season of racing use, those liners turned black, developed cracking, and, yes, chunks began to fall out.

My replacement liners looked great, did not crack, and never came loose. But unfortunately, I’d chosen a poor material for friction. Cast iron has a surface texture that works well against brake lining material. My steel replacement liners were, in a word, slippery.

I never did get around to machining that alternative universe.