Why We Replace Calipers With Your Brake Service
Your brakes always get a workout, whether you’re picking up the kids from practice or heading out into the hills. Every time you press on that brake pedal or your vehicle’s traction control, stability control, or crash avoidance systems are activated, a host of hydraulics and mechanisms work in unison to bring your vehicle to a solid stop.
Because of this, when brakes are worn out, you want to replace more than just the worn-out brake pads. Here’s why.
Calipers Make Your Brakes Work
Yes, there are a lot of other moving parts that go into your braking system, but the calipers provide the clamping force that make it all happen. They take the pressure from your brake pedal and apply it to your brake pads. That, in turn, causes the friction to slow down your vehicle.
Les Schwab Tip: Learn more about brake types in our Complete Guide to Disc Brakes and Drum Brakes.
Sure, a new set of brake pads give you a quick fix to worn brakes. But, we’ve learned over the last 30+ years and thousands of brake repairs that replacing just the pads often leads to other braking issues, such as brake pedal pulsations, brake squeaking or squealing, or worn rubber seals. All of this can cause uneven or faster wear of your brake pads over time.
Built-up grime on your caliper pistons and slides, which become more exposed as your brake pads are wearing thin, can cause caliper malfunction if not addressed when pads are replaced. This short video demonstrates what happens when only the brake pads are replaced and the caliper pistons are forced back into the bore.
The Important Details
Calipers include a handful of parts, including the pistons, piston seals, caliper hardware, and dust boots. To work, all the moving parts in the caliper need to be clean and smooth. Here’s the role that each plays in stopping your vehicle.
- Piston seals flex as the piston moves out. They pull the piston back into the caliper housing. This small part can cause a lot of big issues if they’re not replaced with the brake pads.
- Dust boots protect the caliper from debris and other road grime and dirt. As they get older, dust boots will deteriorate, allowing this grime into the caliper, piston and seal.
- Caliper hardware needs to allow the caliper to float and slide. If the hardware gets rusted or corroded, the pieces can’t perform as well as they should.
Get Complete Brake Service at Les Schwab
Corners aren’t something you want to cut when you’re talking about brakes. When we replace your brakes, you get complete service. This includes premium quality brake pads and remanufactured brake calipers that are as good as the those your vehicle had when it was new.
Remanufactured calipers come with new seals and dust boots, bleeder screws, and hardware, which have been thoroughly cleaned and inspected for quality, performance, and safety.
Bottom line, your car will stop when you hit the brakes. And that’s something we can all appreciate.
Les Schwab Tip: Understand the ins and outs of brake repairs with our Brake Servicing 101: Advice on Making Sure It Gets Done Right.
Never Ignore These 8 Warning Signs of Brake Problems
When you notice a noise related to braking, a difference in braking performance, or a burning smell while driving, get a brake check right away.
Brake servicing is one of those routine maintenance chores you just cannot ignore. Brake parts have a life span and they do need to be regularly serviced and sometimes replaced to work properly.
Fortunately, your car or truck usually gives you some clear signals that your brakes are due. Sometimes they’re harmless noises that don’t require repairs or have simple fixes. Other times not.
Your brakes are one of the most important safety components in your vehicle. So if you notice any of the following common warning signs of brake issues, it’s time to get a professional to check your car, truck or SUV pronto. You’ll drive safer and head off more expensive damage.
1. Brake Light On
When one of the red or yellow brake indicators on your dashboard lights up it may mean you’re just due for an inspection. It could also be your vehicle’s smart electronics alerting you to a problem.
An engaged parking brake could also cause the light to go on. Be sure it’s fully released to confirm that’s not the issue. (And read up on what all your dashboard brake lights mean.)
2. Squealing, Squeaking or Grinding Noises
Hearing a Metallic Squeal While You’re in Motion?
If you start hearing a high-pitched noise that stops when you apply the brakes that’s likely the sound of the brake pad wear indicators. They’re made of steel so they make this sound when they start contacting the rotor.
They’re letting you know that your pads are worn out and need to be replaced before you get rotor damage, which can be an expensive fix.
Grinding Sound When Brakes Are Applied?
Grinding that you also feel in the pedal could mean a number of things. There could just be some gravel or a rock caught in the caliper unit, easily remedied.
But you may have gone too long without brake servicing. The brake pads may be worn through, and you’re hearing metal on metal that could be creating grooves in the brake rotor. Not good.
Grinding could also be an indicator of lack of lubrication in vehicles with rear drum brakes. The brake shoe (the component that presses on the rotor to slow the vehicle) could be scraping on metal contact points like the backing plate, due to rust.
If you hear any of these sounds, get your brakes looked at right away to head off more expensive problems.
3. Wobbling, Vibration or Scraping When Braking
Shaking in the steering wheel or vibration when you apply the brakes may be the result of an uneven rotor.
Brake rotors are big discs that sit inside of the wheels. When you hit the brake pedal, the brake pads hug the rotors, slowing them and your vehicle. You want rotors to be smooth and completely even in thickness.
Over time and thousands of wheel revolutions, it’s normal for the rotor surface to get slight variations. Rust can also sometimes develop. During brake servicing, the face of the rotor is often trued (smoothed and evened out) to correct these flaws.
This work has to be done exactly to your vehicle’s specifications. The tiniest differences in disc thickness — we’re talking thousandths of an inch, about three sheets of paper in width — can cause a wobbly feeling when you brake.
An uneven rotor surface may also cause the rotor to hit one of the brake pads as it spins, causing some of the pad material to transfer onto the rotor in that spot. Then you’ll feel shaking when braking, as the pad hits that bump in the rotor.
Another possible cause of rough braking is the brake caliper not releasing properly. The job of a brake caliper is to squeeze the brake pads against your brake rotors, which slows your vehicle down. It’s the motion of the piston inside the caliper unit that causes this contact.
Due to wear from heat or road debris, the piston can get sticky. It may not retract the pads back into the full “off” position when you let up on the brake pedal.
A fourth cause of bumpy braking could be damage to your brake components from improper wheel lug nut installation. (The lug nuts are the big bolts that clamp your tire and wheel onto the hub of your car.)
Any time tires are removed, it’s crucial for the lug nuts to be put back on in the right order, evenly, at just the right tightness (torque). It has to be done in a star pattern, with just the right pressure. If not, you’ll get uneven, premature rotor wear and be back for service sooner rather than later.
4. Leaking Fluid
If you’re experiencing a soft brake pedal, have a service technician look for fluid leaking from the master cylinder or elsewhere in the brake system.
The master cylinder is the unit that creates the power for your brakes. It has a reservoir like the one for your wiper fluid that contains brake fluid.
When you apply the brakes, this fluid is pushed through thin piping, creating hydraulic pressure. If fluid is leaking from this system, there may not be enough power to force the brake pads to clamp hard to the rotors.
5. Spongy or Soft Brake Pedal
If you notice a difference in the resistance in the brake pedal — it feels “softer,” or sinks all the way to the floor mat when you press on it — it’s a sign you need immediate service. There could be air or moisture in the braking system or a problem with the master cylinder. Generally, in autos with power brakes the pedal should stop 1 to 1 ½ inches from the floor. If you have manual brakes, the pedal should stop more than 3 inches from the floor.
6. Car Pulling to One Side When Braking
This could be caused by a brake hose gone bad or a caliper problem. One brake caliper may be applying more or all the pressure during braking, resulting in unbalanced stopping.
7. Burning Smell While Driving
A sharp, chemical odor after repeated hard braking on steep roads is a sign of overheated brakes or clutch. Pull over immediately in a safe place, check your parking brake to make sure it’s fully released and allow the brakes to cool. If you don’t, you risk heating up the brake fluid to boiling, which can cause brake failure.
If there’s any smoke coming from a wheel, it may be a stuck brake caliper and possibly unsafe to continue driving on without repairs.
8. Bouncing Up and Down When You Stop Short
If your vehicle rocks or bounces with sharp braking, it’s probably not a brake problem at all. Your shock absorbers may need to be replaced.
Not every brake noise or symptom is going to cost you. It could be a harmless squeak from certain types of material in brake pads. There may be dust or moisture somewhere in the braking system that isn’t causing damage. You may just need to add new brake fluid.
But you need to be sure.
Brake parts wear out over time. Self-diagnosing symptoms or delaying brake servicing could put you and your passengers at unnecessary risk. And like with a lot of automotive issues, if there is a problem, the longer you put it off the more you risk big repair bills.
Brake problems far from home are a real inconvenience. Get a free brake check before your next road trip. Find the closest Les Schwab Tires and come on by.
These 3 Useful Driving Tips Will Help Extend Your Brake Life
Follow these good driving habits to help you get the most mileage between brake service:
1. Plan Ahead
Instead of stomping on the brakes just before the stop sign, traffic light or turn, slow down well before the stop. Then the engine does some of the work, reducing wear and tear on your brakes. On the highway, lift your foot off the gas pedal as soon as you see brake lights ahead.
2. Use the Right Braking Method in the Mountains
If headed downhill or over the pass on dry pavement, drive in lower gears. Here’s how: Put your vehicle in the gear that allows you to travel at the safe speed when you start down the incline. Then apply the brakes intermittently with light pressure for about five seconds if your car speeds up, so you maintain the right speed. As in #1, this will let the engine do some of the work.
Note: This only slightly increases wear and tear on your engine. In normal driving, the “front face” of the gears and transmission wear down. With this kind of engine braking, the “back face” of the transmission does the work. You rarely engage the back face, so it’s a good trade between transmission and brake wear.
By balancing engine braking and pumping your brakes, you allow your brake system to cool. Riding the brakes down a long hill generates friction (which creates the stopping power you need). It also creates heat as your brake pads are in constant contact with the rotor. The longer the hill, the more friction and heat you generate, and the greater the wear on all brake system components — pads, shoes, fluid, brake calipers, rotors or drums and hoses.
It’s also a safety issue: Too much heat can also heat brake fluid, causing brake pedal fade, right when you need your brakes most.
Don’t use this technique when you are driving downhill in icy or slick conditions. Start at the top of the hill as slowly as possible and double the distance you’d normally give between you and the driver ahead. Assuming you’re driving a passenger vehicle (not a big rig), leave your auto in normal drive gear and use light, steady pressure on the brake pedal to maintain the right speed.
This allows your antilock braking system (ABS) to kick in instantly if you lose traction. When you use your engine for braking by downshifting, only your drive tires slow the car. (Your drive tires are the front two in a front-wheel-drive auto, back tires in a rear-wheel drive, and all tires if you’re driving an AWD or 4WD vehicle). If the drive tires lose traction and your car starts to slide, the ABS won’t engage and you can lose control.
If you use the brakes instead, the ABS is ready to engage. ABS maintains traction by making sure all four tires slow at the same rate when you apply the brakes. You’ll minimize fishtailing and be able to steer in the proper direction. (Read more about how ABS works.)
3. Follow the Three-second Rule
Pick a stationary object even with the car in front of you — a sign, a building, or a side road all work well. Then count to three. If you pass that object before you get to three, you need to back off and leave more space.
Remember driver’s ed? It was all about defensive driving and safe following distance. This style of driving is not only safest; it’s the easiest on your brake system. Stop-and-go traffic puts high demands on your brakes and decreases brake pad life. You can reduce the wear on your brakes by leaving enough space between you and the car ahead so you don't have to tap the brakes as often.
Save Your Brakes: Drive Smart
Brake pads, shoes, drums and brake rotors will eventually need service for regular wear and tear. Be sure to follow your owner's manual guidelines. If you think something’s wrong with your brakes, or one of your dashboard brake indicators is lit up, don’t wait to get your brakes checked.
Bottom line: Drive defensively, drive smart, and you’ll extend the life of your brakes.
Schedule an Appointment
Brake Servicing 101 - Advice on Making Sure it Gets Done Right
In recent focus groups, people who had paid anywhere from $50 up to $1500 for brake repairs on their cars were interviewed about their level of satisfaction. Regardless of cost, none had complaints.
Why? Because their brakes worked afterward. But there’s more to it.
Here are some basics about brake servicing and what to look for in a reputable shop, so you’re treated fairly — and so the work gets done right the first time.
Brake Service: No Hard and Fast Rules on How Often
It’s hard to pin down the proper interval between brake service. But there are some basic tests:
- Don’t take chances with brake performance. You should never wait to get a brake check if you think something isn’t right with your brake system.
- Understand that you can't easily have a look yourself, because inspecting brakes means putting the vehicle on a lift, removing the wheel, and sometimes taking apart the components.
- You can’t plan on needing brake service on a set schedule, say every 20,000 or 50,000 miles. Brakes can wear out after 18,000 or 60,000. It depends on individual driving habits and road conditions.
Factors in Brake Wear
Driving habits. Are you regularly hauling a trailer or heavy loads? Or do you tend to be a prudent driver who keeps lots of distance between you and the car ahead?
Where you drive. If you’re in stop and go traffic in a daily commute, or regularly driving mountain roads, your brakes will wear more quickly. Off-road travel also puts high demands on brakes. Dirt and grime can degrade brake parts. The quality of parts previously installed. Just like any product, brake parts vary in durability and price. And even premium parts won’t last if they’ve been installed wrong.
Six Questions to Ask When Deciding on Brake Repairs
Recommendations and costs for brake service can be all over the map. So don’t be afraid to ask questions about just what you’re getting for your money. For example:
- What’s included? Some shops advertise a low price to just replace brake pads, but if any other problems are discovered the cost goes way up. A good brake job should include flushing old brake fluid, adding new, resurfacing rotors, and adjusting braking mechanisms.
- Turn-around time. How many days will it take for the garage to get you on their schedule? Can they offer same-day service for the work?
- Quality of parts. If your garage buys from an auto parts house, quality control for parts is in the hands of those who aren’t working on your car. These suppliers may buy from one manufacturer with a special on price today, and another tomorrow. Ask what kind of quality control measures the shop has for parts. You just don’t want to skimp on brake components.
- Approach to replacing parts. There are big differences in how brake service and repairs are done. It’s pretty common at most brake repair shops to pull the calipers off, replace the brake pads, and reinstall the unit.
- Warranty. With people holding onto cars longer, a brake repair warranty can mean a lot. Brake pads are going to wear as the brakes are applied, so at some point, your car or truck will need them replaced.
- Trust. You should feel you’re getting straight talk. A good mechanic is always happy to explain repairs by showing you what’s being done, and more than willing to save the parts removed for you to look at.
But there are many parts of the brake system that work just as hard as the brake pads that may need attention. Built-up grit on pistons can result in brake pads not disengaging when you take your foot off the brake pedal — then your brake pads are going to wear faster, or unevenly.
Heat from the action of the piston can break down the rubber seals, creating a leak in the braking system. And that could result in the brakes fading — or not working at all — when you hit the brakes.
The problem is that it’s not easy to inspect all of these parts — like boots, seals, bushings — without full disassembly. Taking everything apart is time-consuming. It also increases the number of things that can go wrong. Shoddy reassembly is a common reason cars have to come back to the shop following a brake job.
Disc Brake Caliper Assembly
A better option is replacing all the brake components with a unit made to your vehicle’s original specifications. This heads off any problem with other parts wearing out before your next brake pad job. Ask your mechanic which approach he uses.
Ask your shop for specifics on the brake warranty before the service. If it’s a lifetime warranty, does that cover only the parts, or the labor, too? Are free brake inspections included?
Do I Really Need Brake Service?
Brake problems can be confusing to figure out. Some are harmless with little to no repair needed, such as dust in the braking system that causes squeaking. Other issues indicate likely problems with different car parts, such as a worn belt causing a shrill squeal. Not every sound, sensation or smell means you're due for a brake overhaul, but some do.
In order to diagnose, a mechanic will want to know:
- The nature of noises you’re noticing. Are they squealing, squeaking or grinding? Does it sound metallic?
- Exactly where the noises are coming from.
- What causes a noise to start and stop: Revving the engine while in park? Braking? Accelerating? Going over a bump?
- If there are any smells.
- If you feel a vibration.
- Any changes in brake pedal firmness.
No need to worry about taking the time and paying the money for a brake job before you know whether you need it. Here are some symptoms and their possible causes.
Squealing, Squeaking or Grinding
A continuous grinding squeal when you’re underway that came on suddenly could just be a rock caught between the brake pad and the disc. Some types of brake pad material can cause harmless squeaking. The sound could also be from moisture or dust in the braking system that isn’t doing damage. Or hardware may be in need of lube.
But a constant, high-pitched screech coming from the wheel area while you’re driving, which came on gradually and stops while you brake, is likely the brake pad wear indicator. This is a metal tab that contacts the rotor surface once pads are reaching their minimum. This means you’re due for service.
If it’s a shrill squeal coming from the engine area that varies with engine speed, it could be a worn belt (alternator, power steering, fan, water pump, A/C) that’s slipping on a pulley. However, squealing could also mean a failing alternator or bearings. It may take an expert to tell the difference. Squeaking sounds coming from the wheel area can also indicate worn shocks or other suspension parts.
If you’ve got drum brakes in the rear, excessive brake dust or badly worn shoes can cause grinding sounds.
Vibration or Pull
An unbalanced tire can cause vibration in your steering wheel. It costs little to nothing to fix.
Vibration in the brake pedal or steering wheel felt only during braking points to a brake system issue, such as an uneven rotor surface. If you’ve just gotten brake service, it may be that the rotors weren’t resurfaced. Rough braking could also be from the brake caliper not releasing back into a full off position when you let up on the pedal. A less likely cause is a worn suspension part.
Steering pull to one side during braking could be a stuck caliper, bad brake hose, worn-out brake pads or loose suspension parts. If you’re noticing a vibration right after you’ve had a tire rotation or seasonal swap-out, it may be related to tire rebalancing.
A brake pedal that seems too soft when you hit it can mean either air in the hydraulic system, worn-out brake pads or a fluid leak somewhere in the brake system.
A pungent smell could be from oil burning, especially if you’ve recently had an oil change and some overflowed, or you might be driving with the parking brake engaged.
But if the smell is coming from near your wheels — especially in hot conditions while you’re driving in the mountains — it’s possible you’ve been riding the brakes and they’ve overheated. Or, a brake pad or caliper could be stuck, which often comes along with smoke. (Stop immediately in a safe place and figure out what’s going on so you don’t have brake failure.)
Tips Before Getting Service
Ask questions, read your owner’s manual and be aware of the following if brake servicing is recommended.
Be wary if the mechanic says you need brake service when you have 50 percent pads left. If your shop uses percentages to tell when brakes are due, wait until your pads are down to 15 to 20 percent before scheduling. (Les Schwab Tires measures brake pads in millimeters, not percentages. This helps us be more precise about when service is due.)
Find out what’s included. Make sure they do a thorough inspection and get a written quote that includes pad and rotor measurements.
Ask if rotors should be resurfaced or replaced. This service is necessary if you’ve gone too long between brake servicing and grooves have formed on the surface, brake pad material has collected there causing rough braking or the rotor thickness has become uneven. The technician should measure using a micrometer and inform you of rotor thickness. If rotors are getting down to the minimum, it may be better to replace them.
Yes, brake fluid needs to be replaced. Draining old and adding new fluid extends brake component life. It’s common for moisture to get into the brake system. Brake fluid is hygroscopic, meaning it attracts and retains water. When water gets into this sealed system, there’s more risk of corrosion of metal parts and poor braking.
Be cautious about cleaning and lubing. Today’s brake systems typically don’t need to be taken apart and washed. The exception is when you’re experiencing brake squeal or squeaking when your pads still have plenty of life in them and no other cause is evident. It could be glazing, the brake pad’s friction surface getting hardened from heat. In this instance, cleaning and lubing moving components can reduce noise and extend brake life.
Bottom line: Brake sounds, smells, vibration or a dashboard light are not things to guess about and hope you’re right. But you’re not in for an expensive repair job for every problem. Get them checked out pronto by a service shop you trust. (Les Schwab Tires does brake inspections for free.)
Brake Service FAQ
The Basics on Brakes
Why are your brakes squealing?
If your brake light is on, your brakes are squeaky or grinding, if they feel like they are pulsing or grabbing, or they feel “soft” when you hit the brake pedal, don’t wait on a brake check. It not only can be dangerous to ignore such warning signs: small brake problems that are left unrepaired can lead to expensive damage to other parts of your braking system.
The only way to determine if brake noise is harmless or hazardous is to have a thorough brake inspection.
Les Schwab offers the latest diagnostics and repair equipment in the industry for most types of brake systems. Our technicians are trained to get disc or drum brakes working properly on whatever you drive — passenger car, SUV, or light truck, old or new models.
Disc Brake Repair and Services
- Install professional-grade brake pads
- Install Professional Grade Raybestos calipers*, or the equivalent
- Resurface rotors
- Repack wheel bearings when serviceable
- Install new front seals when serviceable
- Replace brake fluid
- Adjust brake components as needed
* PG PLUS™ PROFESSIONAL GRADE Premium loaded calipers are built to be consistent with Federal Safety Standards for quality, performance and safety. Raybestos provides their loaded calipers with Professional Grade premium disc brake pads to satisfy your braking needs.
What do brake pads, rotors and calipers do?
Brake pads are metal plates bonded with sturdy cushioning friction material. The pads are located on each side of the brake rotors — the flat, rotating discs that are attached to the vehicle’s wheels. When you press the brake pedal, the caliper — essentially a clamp housing the pistons and pads — activates the brake pads, sandwiching the rotor. As the pads come into contact, they slow the spinning rotor through friction, which in turn stops the wheels.
Why install Professional Grade® calipers?
Raybestos Professional Grade® remanufactured calipers include new seals, hardware, and brake pads. This provides better caliper operation for proper brake performance.
Why do we use remanufactured calipers in repairs?
Remanufactured brake calipers use a thoroughly cleaned and inspected original equipment metal caliper housing with new brake caliper hardware and seals. Les Schwab uses Raybestos PG PLUS™ Professional Grade® premium loaded calipers or the equivalent, because they are remanufactured to be consistent with Federal Safety Standards for quality, performance, and safety. This caliper comes with Professional Grade® premium disc brake pads.
Why resurface brake rotors?
Whenever possible, we resurface rather than replace rotors, to save you money when new parts aren't necessary. Resurfacing provides a proper finish for new brake pads to mate with, helping prevent brake vibration and pulsation. When a rotor is worn beyond specifications, we install Professional Grade® replacements.
Why replace the brake fluid when performing a brake repair?
Brake fluid naturally attracts moisture, which can penetrate even sealed systems. When it does, it causes the brake fluid boiling point to lower, increasing the chances of corrosion and poor braking. We replace the brake fluid to help reduce this risk, and to prolong the life of brake components.
Drum Brake Repair and Services
- Professional-grade brake shoes
- Resurface drums
- Replace drum brake hardware
- Install new wheel cylinders
- Adjust parking brake
- Replace brake fluid
How do drum brakes work?
Drum brakes work much like disc brakes, by applying friction to a spinning surface to slow and then stop the vehicle’s momentum. In drum brakes, brake shoes press against the inside of a drum instead of a rotor to create this braking action.
Why replace the drum brake hardware?
Drum brakes work using springs which hold brake components in place and return them to position when the brakes are released. Heat affects the spring tension over time. Drum brake hardware is replaced so the brake shoes are held in the proper position, evening out wear and reducing brake drag (failure of the brakes to release completely when the driver’s foot is removed from the pedal).
Why resurface brake drums?
Whenever possible, we resurface rather than replace drums, to save you money when new parts aren’t necessary. Resurfacing the drums provides a proper finish for new brake shoes and helps prevent brake vibration and pulsation. We also offer Professional Grade® replacement drums if they are needed.
Why replace the brake fluid when performing a brake repair?
Brake fluid naturally attracts moisture, which can penetrate even sealed systems. When it does, it causes the brake fluid boiling point to lower, increasing the chances of corrosion and poor braking. We replace the brake fluid to help reduce this risk, and to prolong the life of brake components.
Complete Guide to Disc Brakes and Drum Brakes
When it comes to driving safety, nothing is more critical than your tires and brakes. Here’s a guide to the two types of passenger-vehicle brakes, disc and drum. We explain how they work, how they’re different and alike, why you may have both types on the same vehicle, what kind of wear to expect and what parts will need maintenance.
Braking System Basics
Disc and drum brakes are both based on a hydraulic pressure system. Braking starts with a mechanical force — your foot pressing the brake pedal.
- A piston compresses brake fluid inside the master cylinder located under your vehicle’s hood near your engine. This creates a lot of hydraulic pressure, generating a much bigger force than that of the small effort of pressing down on the pedal.
- The pressure is transferred via the brake fluid through the brake lines then through brake hoses (flexible tubes) that connect the lines with brake assemblies at each wheel.
- There, wheel cylinders convert that hydraulic pressure back to mechanical force. Brake friction material is pushed against the brake disc or drum, slowing or stopping your vehicle.
Basics of Disc Brakes
Disc brakes are found on most vehicles today. They are mounted on the front axle and often the rear as well. To stop a wheel (and your car), a disc brake uses a caliper fitted with brake pads to grab a spinning disc, or rotor.
The caliper is an assembly mounted to the vehicle with a bracket so it frames the rotor. It looks and functions like a c-clamp. It contains:
- Brake pads: metal plates bonded with material that provides stopping friction.
- One or two pistons to push the brake pads against the rotor when you brake.
- A bleeder screw to allow for servicing the brakes and replacing the fluid.
- A rubber piston seal that prevents brake fluid leakage and retracts the piston when the brakes release.
- A dust boot to keep contaminants out of the cylinder.
- Anti-rattle clips that keep the brake pads stable.
The rotor is made of cast iron or a steel/cast iron composite. It’s attached to the wheel hub and turns with the wheel. It’s the surface the brake pads contact. When you step on the brakes, pressurized brake fluid pushes against the pistons inside the caliper, forcing the brake pads against the rotor. As the brake pads press against both sides of the disc, the friction stops the wheel’s rotation.
Rotors can either be solid or vented. Vented ones have more surface area and can more easily dissipate heat.
Two Types of Disc Brakes
There are two types of disc brakes, named after the type of brake caliper used: floating and fixed.
A floating caliper (also called sliding) is the most common type. It has one or two pistons. When the brakes are applied, the inner brake pad is forced against the disc while, at the same time, the caliper body moves closer to the rotor. This action forces the outer brake pad against the rotor.
The fixed caliper design has one or more pistons mounted on each side of the rotor. The caliper itself doesn’t budge: It’s rigidly fastened to a brake caliper bracket or the spindle. When the brakes are applied, only the caliper pistons move, pressing the brake pads against the disc.
Basics of Drum Brakes
Drum brakes are an older style of brake, not common on today’s vehicles. When they are used it is only on the rear axle.
They don’t use brake pads as the friction material. Instead of a caliper that clamps brake pads against a rotor, a drum brake system has a wheel cylinder with pistons that push brake shoes out against the inside of a spinning drum. This contact slows and stops the rotation of the brake drum and the wheel.
Which Is Better?
Although they both operate with the same basic hydraulics, the two types of brakes perform differently. Disc brakes are more efficient, provide better stopping power, dissipate heat easier and work better in wet conditions, all while being less complex.
Most of today’s vehicles have disc brakes at all four wheels. Some base models have disc on the front axle and drum on the rear, to keep costs down. In these models, why are disc put on the front and drum on the rear? It’s due to weight factors. A typical, unloaded vehicle is already about 10 percent heavier in front due to the engine. Then when you hit the brakes, the weight of the car transfers to the front. More braking power is needed there, making it a job for disc brakes.
Here’s more on how disc and drum brakes compare.
Stopping power. Disc brakes apply more braking force faster, resulting in shorter stopping distances.
Heat management. Since they are exposed to air, disc brakes cool better. Drum brake components aren’t as exposed to the air so they take more time to cool down after braking. This can cause brake fade, a loss of stopping power when friction material overheats.
Wet performance. Disc brakes perform better in wet conditions because they are open to the air and can sling water off easily. Plus, the rotors get dried by the pads dragging across them. When water gets inside a drum brake it tends to get trapped inside the drum, so it takes longer for the friction material to dry out.
Weight. Discs are lighter than drum brakes designed to apply the same force.
Emergency brake. A vehicle’s emergency brake is usually applied to the rear axle. This feature is easier to install on a drum brake than to a caliper or inside the hub of a disc brake rotor.
Cleaning. Disc brakes are self-cleaning. The brake pads “wipe” the rotor off when they’re engaged. Drum brakes are closed and are prone to brake dust collecting from the shoes, so they need periodic cleaning.
Repairs. Drum brakes have more hardware and can be more complex to service. But drum brake shoes and wheel cylinders typically cost less to replace than disc brake pads and calipers.
Since a lot of heat is generated by the braking system, plenty can go wrong. The act of braking converts kinetic (moving) energy of the vehicle into thermal energy (heat), subjecting many parts to very high temperatures.
This means a lot of wear and tear even in normal conditions. Some brake components will need to be replaced over the life of a vehicle. There’s no set interval for this since it depends on your driving style, climate and road conditions.
The solution is simply to get regular checks and replace pads, shoes and other components before braking is compromised or other parts get damaged.
Disc brake pads slow the rotor through friction and they wear with normal use. Eventually, they become too thin to function properly. Same thing for drum brake shoes. The friction material on the shoe gets worn out and braking is compromised.
These components should be inspected regularly. You don’t want to wait until pads/shoes wear down to the metal and grind against the rotor or drum.
Other items in the braking system are just as important to keep in good repair. Routine brake service should also include the following.
The brake system should be checked regularly for leaks and fluid should be replaced every few years (usually when the brakes are serviced). Any leak in the master cylinder, the brake fluid reservoir, the wheel cylinders, lines or hoses will reduce the hydraulic pressure that’s created when brakes are activated. Basically, the system can’t generate sufficient force needed to create braking power. You’ll notice you have to push your brake pedal a lot further in order to slow or stop.
Changing out brake fluid occasionally is also essential. This liquid is specifically formulated to prevent corrosion of the brake hydraulic components. But time and moisture contamination can damage its ability to do this important job.
Moisture that infiltrates the fluid will mix with the brake fluid, lowering the boiling point. Even though it resists evaporation, brake fluid will then be more likely to boil and turn into vapor when it gets hot. There will be less pressure in the hydraulic system, causing a low — possibly very low — brake pedal.
Along with moisture, it’s also very common for impurities like rust, road grit or brake dust to get into the fluid, causing internal damage to parts and reducing braking performance.
These rubber rings keep the hydraulic fluid from leaking and protect it from moisture and contaminants. They also cause the piston to return to its off position so the brake pads disengage properly when you release the brake pedal. If this doesn’t happen, you could experience brake drag and premature wear and the vehicle may pull to one side when you brake.
Brake lines are steel tubes that connect the master cylinder to the brake hoses. A spongy brake pedal could mean air has gotten into a line.
Brake hoses carry the hydraulic pressure from the brake lines to the wheel cylinders and calipers. The rubber brake hoses flex, allowing the wheel cylinders and calipers to move up and down with the wheels in relation to the vehicle's frame. If the rubber wears out, your vehicle may pull to one side during braking or you may even get fluid loss and brake failure. If there’s wear inside the hose, small rubber particles can restrict the flow of fluid, causing a brake pull or drag.
The rotor surface can thin unevenly from the brake pad not releasing, leaving the pad in contact even when the brake pedal isn’t activated. When this happens, you’ll experience shaking or wobbling in the steering wheel when you brake.
Brake components are constantly exposed to road debris and brake dust. The dust boot prevents grime from entering the caliper piston. If it fails and can’t do its job, piston damage can occur, causing brake drag, pulls and premature wear.
Failing master cylinders can leak internally. In this case, you may get a low or fading pedal without visible fluid loss. Regular fluid maintenance is important for prolonging cylinder life.
NOTE: There are different approaches to brake service. Get informed about why it’s important to maintain more than just the brake pads or drum brake shoes.
Disc and drum brakes are built differently, with somewhat different advantages. Your vehicle may have both or just disc brakes. Both work as part of the hydraulic brake system. This is a system that’s under high pressure, is subject to lots of heat and can be compromised by road grime, air, brake dust and moisture.
It’s important to get regular brake inspections to keep everything in proper working condition. Refer to your owner’s manual for a recommended schedule. Remember that funny brake sounds, smells or performance are indicators you need to get your vehicle to the shop right away.
What Do Dashboard Brake Lights Mean?
Dashboard brake warning lights might be nothing, or they might mean you need to go straight to the shop. Here’s what those glowing dashboard lights mean:
- My car’s ABS (antilock braking system) light is on. Your car’s ABS has an electrical problem. Go straight to a brake technician. Don’t ignore it, even if you haven’t noticed any change in your car’s handling. The ABS reduces skidding and stopping distance in emergencies, so you want it working perfectly.
- My car’s brake service light is on. Check your parking brake. If it’s engaged, disengage it and see if the light stays on. If the service light goes out, you can drive normally. But keep an eye on it for a while.
- My parking brake isn’t engaged, or the light stayed on when I disengaged it. There may be a problem with hydraulic brake components or brake fluid in the master cylinder may be low. Get your car to the shop without delay.
Pay attention to those warning lights! They can vary by make, model and year, so if you’re just not sure what they mean, get your vehicle in to get checked. You’ll be safer and avoid potentially costly repairs later on.