This month we’re going to talk about early brake systems, but beforewe do that, let’s think about what a brake actually does for a living.Simply put, a brake converts mechanical energy into thermal energy byapplying friction from the pad or the shoe to the disc or the drum.Now we’ve got that out of the way, time for some history. Early inwhat we call the modern era of motorcycles — from 1942 to 1971 — MotherHarley used drum brakes to slow things down. From 1936 to 1957, rearbrakes were of the mechanical variety. A brake pedal linked to acrossover shaft, rear linkage and brake arm converted leg power tostopping power. This system worked OK in its day, but was prone to wearat every mechanical connection.
Manyyears ago I learned the hard way how much trouble you can get into whenone of these points break or lose their cotter key. Needless to say,after I peeled myself off the side of Farmer John’s Pontiac, I paid alot more attention to the condition of each linkage. While Sportstersretained mechanical drum rear brakes until 1979, the first improvementsHarley made on Big Twins occurred in 1958 when hydraulic drums wherefirst introduced. A ¾-inch bore Wagner Lockheed master cylinder actuatedthings, with shoes the same width as the earlier mechanical brake.
Then in 1963, the shoes and drums were made wider for a largerbraking surface area. This fairly stout configuration was used until1972, after which rear disc brakes where introduced. The reasonmanufacturers went to disc brakes has nothing to do with initial brakingperformance. Drum brakes are actually more efficient with their greatercontact area, but are also more prone to fade after repeated use. Oncethe drum gets hot, we can’t convert energy as efficiently.
Discbrakes don’t have the same swept area, but are vastly superior in theheat-dissipation department. This allows the brake to be applied moreoften with a shorter recovery time. Disc brakes from variousmanufacturers have been in use on the rear of our beloved Harleys since1973.
Front brakes were drums from 1936 to 1971, followed by the upgrade tosingle discs in 72. These drum brakes were notorious for not workingwell. Harley riders everywhere where glad this change was made because70 percent of a bike’s total braking power is in the front brake.
In the late ’70s, dual discs were released. This improved stoppingpower even more. Today’s late-model Harley may be equipped with eithertype. After 1982, dual disc applications used a different bore sizemaster cylinder. This is important to remember if you are updating yourhandlebar controls.
The aftermarket has a variety of selections available to improve yourstopping power. Performance Machine’s handiwork is jewel-like in itsprecision. GMA has a fine product for the more economically minded. AndMilwaukee Twins, Hawg-Halters, Brembo, Revtech and Billet Concepts aresome of the other manufacturers that J&P Cycles presently carries.The thing we have to pay attention to is what bore size the new brakerequires. Rear brakes can require 5/8ths (GMA) or 3/4ths. And the truthis, I’ve never seen a current aftermarket caliper that doesn’toutperform the stock brakes. That’s just a fact of life.
Rotors are fast becoming a highlighted feature on many bikes, andpolished stainless steel appears to be one of our more popular sellers.Problem is, this can result in brake pad compatibility conflicts, asituation that can be addressed by changing pads to address our needs.Brake pads come in a variety of compositions. Organic pads are the leastaggressive (less stopping power) but they are certainly more gentle onthe rotors, which improves rotor longevity. On the other end of thespectrum, sintered metal pads are the most aggressive, handing out ahigher stopping ability at the price of increased disc wear. There arepads specifically designed for use with polished rotors to reduce wear.What’s best for you? To make that decision, you need to think about howyou ride. Do you have a smaller bike that you insist on throwing hardinto the corners? Then use a more aggressive pad. Would you describeyourself as more of a cruiser? Then a softer pad’s for you. Are youtricking things out for maximum appearance? Polished rotors with a paddesigned for that use is your ticket.
But that’s why we’ve got tech specialists here at J&P Cycles whocan answer your specific questions about brakes — and anything else thatsits on two wheels. Give us a call.
