Brake Calipers in Cars: Definition, Uses, Function & More
What Are Brake Calipers?
Brake calipers are a key component of disc brake systems, which are the most common type of brake system in modern vehicles. According to Goodyear, “A caliper is part of the disc brake system, the type most cars have in their front brakes. The brake caliper houses your car’s brake pads and pistons. Its job is to squeeze the pads against the rotor to stop your car” (source).
The main components of a brake caliper include:
- Brake pads – The friction material that presses against the rotor to stop the vehicle.
- Pistons – Apply pressure to push the brake pads against the rotor when the brakes are applied.
- Bleeder valve – Allows air to be bled from the brake fluid system.
- Brake fluid inlet – Where pressurized brake fluid enters from the hydraulic brake lines.
- Caliper housing – Holds all the components together and attaches to the vehicle.
Brake calipers play a critical role in the overall braking system. When force is applied to the brake pedal, it presses on the pistons via hydraulic pressure. The pistons then clamp the brake pads against the rotor, creating friction that slows the vehicle’s wheels and stops the car.
How Do Brake Calipers Work?
Brake calipers work through hydraulic pressure. When the brake pedal is pressed, brake fluid is forced through the brake lines into the brake calipers. This hydraulic pressure causes the pistons inside the caliper to extend and push the brake pads against the rotor.
The friction between the pads and the spinning rotor causes kinetic energy to be transferred into heat energy, which slows the rotation of the wheels and brakes the vehicle. The harder the pedal is pressed, the greater the hydraulic pressure in the calipers, and the more force applied by the pads against the rotor to stop the car.
Floating calipers have pistons on only one side of the rotor. The caliper housing then slides to allow even pressure between both brake pads. Fixed calipers have pistons on both sides of the rotor for balanced braking power. Performance brakes may use up to 6 or more pistons per caliper for maximum stopping force.
Properly functioning brake calipers are critical for safe braking. If the caliper pistons get stuck or seize up, the pads could drag on the rotor. Pads that aren’t fully retracting can cause brake overheating, uneven brake wear, pulling to one side when braking, and brake noise or vibration.
Types of Brake Calipers
There are several different types of brake calipers, each with their own design, advantages, and uses:
Floating vs Fixed:
Floating calipers are the most common type found on most vehicles. As described by Haynes (https://haynes.com/en-au/tips-tutorials/understanding-different-types-brake-calipers), they have one or more pistons on one side of the rotor only. The caliper itself can move slightly allowing the pads to align properly with the rotor as they wear and reduce drag. Fixed calipers are mounted solidly and don’t move. They have pistons arranged on both sides of the rotor which helps provide even wear of the pads. Fixed calipers offer more precision and control compared to floating.
Single vs Multi-Piston:
Most standard calipers use a single large piston to apply force to the brake pads and clamp the rotor. Performance oriented multi-piston calipers utilize two, four, six, or even eight smaller pistons. As JD Power describes (https://www.jdpower.com/cars/shopping-guides/what-is-a-brake-caliper), this allows for more even distribution of force leading to better brake performance under hard use.
Materials Used:
Most factory calipers are made from cast iron which provides good strength at low cost. Performance models may use aluminum to save weight or more exotic materials like carbon fiber in ultra high end applications. According to Haynes, brake calipers must withstand extremely high temperatures and pressures, so the right material choice is critical.
Brake Caliper Design and Engineering
Brake caliper design involves optimizing a number of factors to achieve maximum braking performance. Some key considerations include:
Load requirements – The caliper must be able to withstand the clamping force needed for effective braking. This depends on factors like vehicle weight and brake pad friction material.
Stiffness – The caliper body needs sufficient stiffness to avoid deformation under load. This ensures even pad wear and proper piston movement.[1]
Thermal considerations – Brake heat is dissipated through the caliper structure. Design aspects like web thickness, cooling fins and airflow optimize heat management.
Size and weight – A more compact and lightweight caliper reduces unsprung weight, benefiting ride quality and handling.
Ease of manufacture – Design choices affect manufacturability. For example, avoiding complex contours and minimizing part count.
Material selection – This impacts strength, weight, corrosion resistance and cost. Common materials include cast iron, aluminum and phenolic resin.
Optimized caliper designs enhance braking effectiveness through even pad wear, piston seal life, heat dissipation and pedal feel. Advanced engineering also strives to improve reliability while reducing size, mass and cost.[2]
Brake Caliper Maintenance
Proper brake caliper maintenance is critical for safe braking performance. Brake calipers should be regularly inspected for wear and leaks. The caliper slides and pins should also be lubricated to prevent them from seizing up. Replacing pads and rotors is another part of routine brake caliper maintenance.
Inspecting the brake calipers involves looking for any leaks or damage. Leaking brake fluid can indicate worn caliper seals that need to be replaced. Cracks or improper piston movement also signify that the caliper needs rebuilding or replacing. Another inspection point is the caliper slides and pins. These should move freely without sticking or binding https://weberautomotive.com/brake-caliper-servicing-whats-that. Excessive play or difficult sliding means they need lubrication or possibly replacement.
Lubricating the caliper slides and pins helps prevent them from seizing up and causing uneven brake pad wear. This involves cleaning off any debris, applying brake lubricant, and reinstalling the hardware. Silicone-based lubricants work well for the high temps of brakes. Lubrication should be done whenever the pads are replaced or if sticking is noticed.
The brake pads and rotors are wear items that require periodic replacement as part of caliper maintenance. Pads should be inspected at every oil change or tire rotation. They should be replaced once they reach the minimum thickness, usually around 3-4mm. The rotors should be resurfaced or replaced when warp, thickness variation, or deep grooves are present. Pad and rotor replacement keeps the calipers operating properly.
Brake Caliper Repair and Replacement
Brake calipers are a crucial part of your vehicle’s braking system, so it’s important to know the signs of a failing caliper and when to replace it. Some common signs that your brake caliper needs repair or replacement include:
- Uneven brake pad wear – If one brake pad is wearing down faster than the other, the caliper piston may be sticking.
- Noise when braking – Squealing, grinding or popping sounds can indicate an issue with the brake caliper.
- Pulling to one side – If the vehicle pulls to the left or right when braking, the caliper on that side may be stuck.
- Leaking brake fluid – Damaged caliper seals or pistons can cause brake fluid leaks.
- Low brake pedal or excessive pedal travel – These symptoms point to potential problems with caliper pistons.
Replacing a faulty brake caliper involves the following general steps:
- Lift the vehicle and remove the wheel to access the brake assembly.
- Detach the brake hose and brake line from the caliper.
- Remove the caliper mounting bolts and slide off the old caliper.
- Clean the brake assembly and inspect the brake pads, rotors and slide pins.
- Install the new caliper and secure with mounting bolts.
- Reconnect the brake hose and bleed any air out of the brake lines.
- Reinstall the wheel and lower the vehicle.
It’s recommended to replace both calipers on the same axle when servicing brakes to maintain even braking. Always refer to a vehicle service manual for the proper caliper replacement procedure. Improper caliper service can impact brake safety and performance.
For more details on brake caliper replacement, check out this step-by-step guide: https://www.autozone.com/diy/brakes/how-to-replace-a-brake-caliper
Brake Caliper Manufacturers
There are several major manufacturers that make brake calipers for original equipment and the aftermarket. Some of the top OEM brake caliper manufacturers include:
- Brembo – Known for high-performance brakes used by many luxury and sports car brands like Ferrari, Porsche, Lamborghini, as well as performance upgrades (Source)
- Akebono – Supplies OE brakes for many Japanese automakers like Toyota, Nissan, Honda, and more (Source)
- Aisin – Brake supplier for many Toyota vehicles (Source)
- Continental – Major brake system supplier for European makes like Volkswagen, BMW, Mercedes-Benz (Source)
Some of the leading aftermarket brake caliper brands include:
- Wilwood Engineering – Manufactures performance racing brake upgrades (Source)
- Power Stop – Budget-friendly OE replacement brake parts (Source)
- EBC Brakes – Wide range of OE and performance brake parts (Source)
- Centric – Quality OE replacements (Source)
Brake Caliper Troubleshooting
Brake calipers can develop a number of problems over time that can affect braking performance. Being able to properly diagnose brake caliper issues is important for safety and preventing further damage.
Some common brake caliper problems include (Source):
- Leaking fluid – This could indicate a blown seal or cracked housing.
- Sticking pistons – Dirt or corrosion can prevent the pistons from retracting properly.
- Seized pistons – This can cause excessive heat and uneven pad wear.
- Loose mounts – The caliper needs to be securely fastened to function properly.
- Excessive play – Too much caliper movement can affect clamping force.
To diagnose brake caliper issues (Source):
- Inspect for leaks around seals, hoses and fittings.
- Check brake pad thickness for uneven wear.
- Look for cracks or damage to the caliper housing.
- Test the caliper piston operation and movement.
- Listen for odd noises like squealing or grinding.
Addressing brake caliper problems right away is important to avoid safety hazards and more extensive repairs down the line.
Brake Caliper Upgrades
Upgrading your brake calipers can significantly improve braking performance. Larger brake calipers allow for larger brake rotors and pads, providing more braking power and better heat dissipation. Some key benefits of brake caliper upgrades include:
Improved stopping distance – Larger rotors and pads give upgraded brake calipers more bite, allowing you to stop faster. This is especially beneficial for high performance driving.
Reduced brake fade – Upgraded calipers are designed to resist heat buildup and brake fade during repeated heavy braking. This provides consistent braking during extended use.
Better pedal feel – Stiffer calipers and larger rotors give a firmer, more responsive pedal feel compared to stock brakes.
Increased brake pad and rotor life – The added thermal capacity of larger rotors keeps temperatures lower, reducing wear on pads and rotors.
Customizable options – Aftermarket brake kits allow you to pick the exact brake caliper, rotor, and pad combination to match your needs.
Common brake caliper upgrades come in the form of big brake kits. These kits include larger calipers, rotors, pads, brake lines, and hardware for a complete brake system upgrade. Brands like PowerStop and Brembo offer brake kits with various levels of performance at different price points.
The Future of Brake Calipers
Brake calipers are continually evolving as new technologies emerge and innovations are made in the auto industry. Here are some of the new and upcoming technologies related to brake calipers:
Brembo has introduced a brake-by-wire system that greatly improves response time compared to previous systems (The Future of Brakes – Brake Systems of the Future, continental.com). This technology allows for more precise brake modulation and control.
Brembo is also developing the Lybra project, which uses a fiberglass shim instead of a metal shim for brake pads. The fiberglass shim reduces braking noise while maintaining performance (The braking system of the future, bremboparts.com).
Continental is working on “intelligent” brake systems for automated and autonomous vehicles. These advanced systems can independently monitor surroundings, adapt to situations, and provide optimized braking functionality (The Future of Brakes – Brake Systems of the Future, continental.com).
Overall, brake caliper innovation is focused on improving performance, efficiency, safety, noise reduction, and integration with automated driving systems. As vehicles continue to evolve, brake calipers will need to advance as well. Expect to see the emergence of smarter, more capable brake systems in the future driven by new technologies.