Tech talk - Know Your Brake Calipers

Fast bikes (FB): What is the purpose of a brake caliper?

Les Barton (LB): The brake caliper is the device that makes the magic happen in terms of braking power, as it’s the operation of the pistons within, on a brake pad, which then comes into contact with the brake disc that slows down your bike. Back in the day, motorcycles had drum brakes, which were absolute rubbish – they couldn’t cope with heat or changes in weather and offered nowhere near the same amount of braking power. Thankfully, the introduction of brake discs meant drums were ditched by most motorcycle manufacturers many moons ago.

FB: How does a brake caliper work?

LB: Surprisingly, a regular brake caliper is a pretty simple object. Essentially, a caliper, or two on the front end of most modern sports bikes is attached to the bottom of the fork leg. Squeezing the brake lever pushes a hydraulic piston, which sends fluid down the brake lines and into the caliper. The pistons inside the caliper are then forced outwards, pushing the attached brake pads into contact with the brake disc rotor.

FB: What are the main issues with a faulty brake caliper, and how are they fixed?

LB: There are a number of issues that can be associated with brakes, but only a few that are attributed to the calipers themselves, and as they’re a relatively simple design, they’re quite easy to fix. As you have many different components that make up a braking system, a lot of the time the issues can arise from elsewhere, but if you feel like your brakes aren’t working up to scratch, it’s always worth removing and checking the caliper. It can show you some tell-tale signs of problems, such as any leakage from the brake hose or within, around the pistons. If you have this, you’re going to need to service the calipers and replace the internals. It’s also worth checking the cleanliness, as something as simple as excess grime and dirt within the caliper can make a big difference to the performance of the entire braking system.

FB: What constitutes a bad caliper?

LB: A few things, the worst being one that’s been left for years and years! One of the biggest issues you’ll encounter will be an old caliper that has seized. This means that the piston is wedged within, and the pads are then stuck on the disc, which will make the machine feel like the brakes are stuck on – if you can move it at all. If you do get going, it will cause some serious heat on the pads! This means it’s wise to completely disassemble, clean and rebuild the caliper if you aren’t going to purchase a new one, and although it does take a little bit of time it’s not the most strenuous activity in the world.

FB: How good are standard calipers?

LB: Standard calipers nowadays are absolutely incredible, with the high performance examples offering more power and precision than the racing models would’ve done 15 years ago. Even on lower-end machines, calipers are getting better and better, although it will usually be the ABS that kicks in before the caliper runs out of steam. An example of how good standard calipers are is the fact that all superstock racing machines have to run them.

FB: What are the advantages of aftermarket calipers?

LB: Yes, standard calipers are good, but everything can be improved! On a race track, aftermarket calipers are a lot more efficient in dispersing the heat, while in a paddock like World Endurance, they offer a quick release system for ease when doing wheel changes for speedy pit stops.

FB: How much different is a road-based caliper to a full on racing one?

LB: Although they’re fundamentally the same in design, like all racing products they do differ a fair amount in a sense that they’re functionality and threshold is much higher. Take a MotoGP-spec Brembo caliper – those things operate about 80 degrees higher than a standard caliper and are made so efficiently that teams can bleed them quickly, mid-session.

FB: What difference do the amount of pistons make, and why is more better?

LB: It’s easy; if you double the amount of pistons, you’re doubling the clamping force the brake pad has to the brake disc, therefore increasing the braking power. You’ll see on higher-spec front calipers that you’ll get four pistons, whereas on the rear you’ll get one or two. This is because the rear is used a lot less, with a lot less power needed.

FB: What’s the best way of maintaining calipers?

LB: The best way to do so is by gently removing the calipers and using a proper brake cleaner within. You can use a toothbrush here, or some very fine wet-or-dry paper, but always be incredibly careful when reassembling.