Much as we all might like going fast, it's our ability to stop quickly — and securely — that really counts. While mechanical drum brakes were the norm for decades, hydraulic disc brakes took over beginning in the early 1970s. Self-cleaning, self-adjusting and typically stronger than drums, hydraulic brakes, outside of the occasional fluid flush and change of brake pads, also tend to be pretty much maintenance free. Occasionally, however, they require a little more attention, like a brake master or caliper overhaul.
Although it's impossible to predict when you'll need to overhaul your bike's hydraulics, it's a fair bet that any bike that's been sitting for long — say, two or more years — will need at least a fluid flush and possibly a complete overhaul. Brake fluid is hygroscopic, meaning it's water absorbing. When hydraulic brake systems sit unused, moisture can get trapped under dust boots and work its way into the seals. Once absorbed, it turns brake fluid into a sludgy, seal-killing goo.
That's dangerous, of course, because if your brakes don't work well, you might find yourself not working too well either. Fortunately, with most of the older bikes we ride, a brake caliper rebuild is a pretty straight-forward proposition. The caliper we rebuilt for this piece is the tried and true Brembo brake: the Brembo F08 twin-piston caliper. Used by just about every European bike manufacturer in the mid-1970s up to the early 1990s, they're robust, quality units that give excellent service with very long life. Parts are readily available from a variety of sources like Bevel Heaven and MG Cycle, and they're dirt cheap; caliper seal kits are less than $20 each, pistons about $25 a pair.
They're also quite easy to rebuild. Budget about two hours for your first rebuild, but after that you can probably knock one out in an hour. That said, patience — and cleanliness — should be your guide. You literally trust your life to your brakes, so exercise caution and double-check your work to ensure a successful overhaul. When in doubt, replace worn out items and don't leave anything to chance.
We’ve provided a Step-By-Step Rebuilding Guide, but we’d like to emphasize that readers should always have a good shop manual specific to their bike for reference. For a job like this, the proper shop manual will ensure correct removal and installation of your brake caliper and final bleeding of the hydraulic system. There are always nuances from bike to bike. Make sure you understand yours. MC