The brake system in your car works by brake calipers gripping the rotor to stop and releasing it to start moving again. Sometimes it feels like the wheel is still gripped even after releasing the brake pedal. What causes brake calipers not to release?
Imagine if you couldn’t stop your car as and when you need to because you have faulty brake calipers. Driving would be a nightmare. The brake system in a car is often taken for granted when it is in proper working condition. It is only when it begins to fail that most people realize just how important it is.
It is arguably the most important safety component in the car. Even if you are not a professional mechanic, it is important to understand the basic working of this system and what to do when something is out of order.
The typical braking system is made up of brake calipers, a rotor (or disc) and brake pads. Let’s take a closer look at brake calipers.
How Brake Calipers Work
Most modern cars use disc brakes. With this type of brakes, the wheel is attached to a metal disc or rotor which spins along with the wheel. The braking system operates by stopping the rotor, which in turn stops the wheel when the driver steps on the brake pedal. The brake caliper fits over the rotor like a clamp. Both inner sides of the caliper have metal plates bonded with friction-producing material (brake pads). It is the brake pads which come into contact with the surface of the rotor.
When you step on the brake, brake fluid exerts hydraulic pressure on the piston in the caliper, forcing the brake pads against the spinning rotor. This is how the car comes to a halt. What causes a brake caliper to retract?
When you release the brake, hydraulic pressure decreases allowing the brake pads to pull away. The released grip enables the rotor to spin freely again.
What Causes Brake Calipers to seize?
The caliper moves in two directions: inwards to grip on the rotor and outward to release it. A faulty caliper therefore fails to either grip or retract.
A seizing brake caliper fails to grip the rotor as it should when you step on the brake pedal, or fails to release. Although this is a fairly uncommon problem, it is important to know why it happens. Here are some possible causes.
Caliper Slides: The caliper contains grooves that hold the brake pads and allows them to slide in when the brakes are applied and out when the brakes are released.
Sometimes the shims of the brake pads get stuck in the grooves because of rust or accumulated dirt. When this happens, the brake pads cannot easily slide in to grip the rotor and also cannot easily slide out when the brakes are released.
Caliper Bolts: These bolts also have slides that need to stay well lubricated for smooth movement. They have rubber boots that help keep in the lubricant so caliper bolts ordinarily don’t need frequent lubrication. Sometimes mechanics accidentally tear these boots when they are installing new brake pads. This leaves the bolt slides exposed to rust which hampers smooth movement.
Caliper Piston: The piston pushes the brake pad onto the rotor. Some vehicles have single pistons and others have multiple pistons. Like caliper bolts, pistons have rubber boots that help protect, lubricate and seal them.
Careless mechanics can easily tear these boots as they go about replacing brake pads. This leaves the piston exposed to dirt and rust. Both of these can prevent the piston from sliding smoothly.
What Causes Brake Calipers Not To Release?
Sometimes the brake system fails not in the caliper’s ability to grip the rotor but in how efficiently it releases that grip when the brake is released.
The feeling that the brakes are still applied even after you have released the brake pedal is known as brake drag. A worn-out brake hose often causes it. The purpose of the hose is to carry brake fluid which exerts pressure on the piston.
Ideally, when the brake is released, the fluid should flow back into the reservoir, therefore releasing pressure on the piston, which allows the brake pads to lift off the rotor.
When the hose wears off internally, a small piece if it’s inner lining partially breaks off leaving the rest of it still attached to the wall of the hose. This creates a flap-like section that acts as a valve. It allows brake fluid to flow smoothly toward the piston for proper braking.
When the brake pedal is released, the fluid doesn’t flow back as it should but instead continues to exert pressure on the piston. This is what causes the driver to feel like the brakes are still applied when the pressure on the brake pedal has been completely released.
What Would Cause A New Brake Caliper To Seize?
You just replaced your brake calipers but one of them seems to be seizing. What could be the problem?
A collapsed brake hose: Sometimes the brake hose is not worn out but collapsed. When you step on the brake pedal, brake fluid is forced through the hose and easily flows through it because it is under significant pressure. When you release the brakes, the fluid is not under much pressure so it cannot get through the collapsed hose. When this happens the brake pads retain the grip on the rotor even after the brake pedal is released. The best remedy for a collapsed brake hose is replacement.
Misaligned Caliper: The repair technician may have failed to align the caliper with the rotor properly. This will definitely cause a drag. This is caused by a severely warped rotors and/or brake pads.
If you suspect this might be the problem with your car, take it to a professional mechanic who should visually inspect the alignment before dismounting the caliper or any other part of the assembly.
How to Fix a Sticking Brake Caliper
Sometimes brake calipers get stuck or frozen. When this happens the caliper cannot move smoothly to clamp the rotor. If it freezes on the rotor, it cannot completely disengage from its surface. This means the brakes are always lightly applied, which makes driving difficult and causes a lot of stress on the entire brake system. Sometimes the car is completely immobile and you have to call in help from a professional who knows how to unfreeze a brake caliper.
Tell-Tale Signs of a Sticking Brake Caliper
When brake calipers are in good working order, you will be able to slow down and bring the car to a halt quite smoothly. When these calipers develop problems the effects are felt when you apply the brakes. These are some typical signs of faulty brake calipers.
- The car jerks or pulls to one side when brakes are applied.
- Continuous grinding, squeaking and squealing of brakes.
- The brake pedal feels abnormally spongy or abnormally hard.
- You need to press the brake pedal very hard just to slow down.
- There is leaked brake fluid which could be seen around the wheel or in the engine compartment.
- Heat coming off the wheels
- The ABS (antilock braking system) warning light is on.
If you suspect a stuck caliper, pull over as soon as it is safe to do so. Turn off the engine and put the gear in park. To check if excess heat is coming from the wheel, place your hand close to the wheel but don’t touch it.
How Do You Fix A Seized Caliper?
What do you do when your caliper is sticking? Most cases of seized calipers appear due to a skewed pad or brake pads sticking to the rotor.
In this case, you don’t have much to worry about. All you need is a thorough cleaning and some lubrication. Lubricate the entire parking brake system. Remove the brake pads and slides and ensure they are well-greased.
It is also advisable to inspect all the brake components, including seals and pistons, to ensure they do not hang up on the piston bore or caliper.
Even after carrying out all this inspection, the best way to repair pads stuck on the rotor is to resurface the rotor and then replace the brake pads. Another alternative is to purchase refurbished brake calipers.
How Smooth Should Brake Rotors Be?
Rotors must be smooth for optimum braking power. After continuous use a rotor develops grooves along the lines on which the brake pads grip it. Light shallow grooves should not be cause for worry.
When they get deeper, they decrease the surface area, which comes into contact with the brake pads.
The result is reduced stopping power. Heat spots are another possible problem. They occur when new brake pads are not bedded properly and pad deposits accumulate to form cementite. It prevents the brake pads from gripping the rotor properly and also reduces its ability to dissipate heat.
Another problem related to grooves is warping. It is most commonly caused by overheating which happens due to excessive aggressive braking.
If your rotors are grooved and warped, you can have them resurfaced. This is a mechanical process similar to filing. The mechanic shaves off bits of metal off the surface of the rotor to make it smooth again.
Once perfect leveling is regained, the brake pads sit fully on the rotor, and any noise which could be heard when braking is eliminated.
What Is The Minimum Thickness For Brake Rotors?
How many mm should brake rotors be? This is where minimum rotor thickness specifications come in. Every rotor has a minimum thickness indicated on its casting and in the factory service manual. This is what the brake mechanic uses as a guide to determine if the rotor can be resurfaced any further or must be discarded. A thinned rotor loses its ability to absorb and dissipate heat. It is also gets weak so it can easily break or crack.
How to measure rotor thickness
- Using a micrometer, measure the thickness 10mm (0.4 inches) inside the outer circumference every 1/8 of a rotation (45 degrees)
- Compare the minimum thickness specification on the rotor to the smallest measured value. If the smallest value found is smaller than the minimum specification, the rotor must be replaced.
When should rotor thickness be checked? In the past, rotors were designed to be thick enough to last at least 2 brake pad replacements. With this kind of durability, the general rule among brake mechanics was to check rotors after 2 pad replacements.
Nowadays rotors are designed thinner to reduce overall weight of the vehicle as well as cost. With these changes, it is now recommended that rotor thickness be measured every time the brakes are serviced. In some states this is a legal requirement.
In other states, auto repair shops and stores must retain rotors found below minimum thickness as a safety precaution.
When to Replace Brake Pads
Brake pads work along with the rotor so even if it is in perfect condition and brake pads are not, the entire system is bound to fail. How can you tell when it is time to change the brake pads? Here are some telltale signs to look out for.
Screeching and Squealing: This is usually the first indication that your brake pads are due for replacement. The squealing sound is only heard when you step on the brake pedal. It is however not a definite sign of worn brakes because it could also be caused by wet or damp conditions after a rainstorm. If the squealing and screeching persists for a few days you can confirm that the brake pads need replacement.
Thinned brake pads: Take your car to a repair shop and have them check the thickness of the pads. New brake pads come with about 12mm of friction material. They need to be replaced when it gets to about 3mm (¼ inch)
Indicator Light: In some vehicles, there will be an indicator light on the dashboard when the brake pads require replacement.
If you continue driving on worn thinned brake pads, you will hear a deep metallic grinding sound from the brakes. It comes from metal- to- metal contact between the rotor and the caliper after the pad is completely worn out.
Can You Change Brake Pads Without Changing the Rotors?
We have all heard of repair technicians who recommend replacing parts even when it is unnecessary just to get a few more bucks out of your pocket. If you have fallen prey to this you know how cheated one feels when they realize they spent money on a whole lot of work which really didn’t have to be done.
The next time you take your car to a repair shop you may be tempted to disregard their advice for extra replacements and go with what feels ‘alright’ on your car.
What happens if I replace brake pads but not rotors?
While it is important to be proactive and cautious, this can pose a huge safety risk especially if you don’t understand how the proper working of one part relates to the efficiency of another.
How Rotors and Brake Pads Work
Have you ever wondered what goes on in your car’s system when you slow down and stop? It is one of those things we never think about until something goes wrong.
The main components of the braking system involved are the rotor, brake caliper and brake pads. When you step on the brake pedal, the brake caliper clamps on the spinning rotor to bring it to a complete stop.
On each side of the caliper are metal plates lined with friction-friendly material (brake pads.) When the pads clamp on the surface of the rotor, its kinetic energy is converted into thermal energy.
This explains why it is better to slow down gradually and stop than to suddenly slam on the brakes. The latter produces a lot of heat which is harmful to the system.
Rotor Resurfacing
Rotors have to withstand a tremendous amount of heat by virtue of their function. After tens of thousands of miles worth of heat cycles, rotors sometimes get warped. They also develop grooves as a result of brake pads wearing down on the surface.
When this happens you end up with a warped rotor with uneven grooves where the brake pads repeatedly clamp on it. This can be remedied through resurfacing, also called turning.
This is a mechanical process similar to filing where small amounts of material are removed from the surface of the rotor to get rid of grooves, warps and even rust. It leaves the surface perfectly even.
There is a minimum allowable thickness for rotors. Resurfacing reduces the thickness of the rotor. When resurfacing your rotors, make sure they remain above the minimum thickness.
If they are too thin, they cannot withstand much heat and could easily break. You don’t want to compromise your safety. You or the technician can use a micro-measuring tool to measure the thickness.
Remember that all new rotors are 45mm thick as a basic guide. The minimum allowable thickness is 37mm. Some rotors have manufacturer-specific minimums, which are clearly marked on the casting.
Do You Have To Resurface Rotors When Changing Pads?
There is no clear-cut rule here. It depends on the condition of the rotors at the time. If they are in good working condition, there is no need to change them when you replace brake pads. Here are a few factors to consider.
Brake pulsating or shuddering: If you have even the slightest feeling of pulsating or shuddering when you step on the brake pedal, it means the rotor(s) have some grooves on the surface, and there is a need for some resurfacing.
Rotor thickness: As long as the rotors are above the minimum thickness, braking efficiency will not be reduced. If they are below the minimum, replace them.
If you are getting close to the limit and have some heavy use planned for the next few months, changing them is a good idea to avoid returning to the repair shop in a few weeks.
The rule to remember is that brake pads should be replaced every 10,000 – 20,000 miles. Rotors last significantly longer and only need replacement after 50,000 – 70,000 miles.
Considering this recommendation and the normal wear of the rotor, you will find that the average rotor typically takes only one resurfacing along with a brake pad replacement.
The rotors will be below minimum thickness when the car is due for the next brake pad replacement.
What Happens If You Change Your Brake Pads Without Turning?
As mentioned earlier, changing brake pads and retaining the rotors is fine if they are still in good condition. If they are warped and have deep grooves, you will run into some challenges later.
Firstly, the new pads will wear out faster because the grooves in the rotor will wear in the new pads, reducing their lifespan. You will also experience reduced braking efficiency because the pads don’t make full surface contact with the rotor.
This is a safety risk because the car will not stop as quickly as it should if you have an emergency braking situation.
Resurfacing rotors at home below the minimum allowable thickness could get you on the wrong side of the law. In the event of an accident attributed to substandard rotors, you will be considered responsible for any injuries or death in such an accident.
If you are not a professional mechanic, always take your car to a professional for this work. Most professionals will give you sound advice as far as need for replacement of parts is concerned. If you doubt that the advice you are getting is sound, get a second opinion and do some basic online research.
Can You Replace Just One Brake Caliper?
The brake caliper on the front left wheel is faulty and needs to be replaced. Must you replace the right one as well? Auto experts seem to differ on this. Some say there is no need to replace both while others say you must change both even if only one is faulty. Here is what the two school of thought argue.
Change 1: This group of experts says it is perfectly fine to change one faulty brake caliper and leave the other intact. They argue that unlike brake pads, brake calipers on the right and left side don’t work in tandem and do not rub on each other.
The caliper fits over the individual rotor and does not come into contact with the other. It is also quite costly to replace both calipers so why replace both when you don’t have to?
Change both: Assuming both brake calipers were installed at the same time, by the vehicle manufacturer, it is not absurd to assume that when one caliper fails, the other will most likely fail soon. Save yourself the time and hassle of having your car in the repair shop again. This group also argues that the calipers may not be identical and one may be stronger.
This will cause the car to pull to one side when you step on the brake pedal (brake pull.) Some calipers have pistons made of metal and other pistons are phenolic. Some mechanics say you will experience brake pull if the pistons in the two calipers are not made of the same material.
At the end of the day the decision to change one or both calipers lies with the owner. The only time it may be necessary to change both calipers even if one is not faulty is if you use contaminated brake fluid.
Contaminated brake fluid is dangerous because it can easily block the pistons. If one caliper is affected, the other is also very likely to be affected similarly.
Replacing Brake Rotors
Rotors are not designed to last through the life of the car. You will need to replace them at some point. They generally need to be replaced anywhere between 15,000 and 70,000 miles depending on the type of brake pads used and your specific driving style. Have your repair technician use a micrometer to measure the center and lip of the rotor and determine if it is below minimum thickness. If it is, replace it.
Is It Okay To Replace Just One Brake Rotor?
As a general rule, always replace your rotors in pairs. If you can’t afford to replace all four, replace the front two and the rear two later. Never replace singles.
The primary reason is a safety issue. Even if the new rotor is identical to the old one, the two cannot operate at the same rating because one is more worn out. It would be even worse if the new one is a different brand from the old one.
When the specifications and ratings are different, you will notice one side stopping harder than the other, which is quite risky.
Another reason to replace both rotors is heat. When one side has a new rotor, and the other an older one, the heat dissipation is better on the side with the new rotor.
The side with the older one will experience brake fade causing the car to pull in one direction. This may seem harmless at low speed but can be extremely dangerous at high highway speeds.
Finally, don’t forget that your brake rotors were installed simultaneously and have the same life span. If you replace your one because it is worn out, the other is almost due for replacement. This is not necessarily the case if you are replacing it because you hit a bump too hard and it broke.
Conclusion
The brake system in your car is one of the most important ones. Thanks to this system, the rotor is easily halted to allow you to slow down and stop and release when you want to start moving again.
FAQ
What is the average replacement cost for brake calipers?
The cost of replacing brake pads is different for every car and truck. You can get a package with both brake pads and discs saving you money.
Should I have more pistons in my brake calipers?
Most of the brake calipers you will find in most cars have one piston. Unless you have upgraded your car engine or added to its performance in any way, your brakes should be fine that came off the manufacturer’s shelf.
What are red brake calipers?
These are mostly present in sports cars. The color you choose does not really affect how the calipers operate, but the norm is for high-performance cars to come with red ones.
Related Posts
- Bosch vs Bendix vs Wagner: Which Brake Pads Offer the Best Value
- How to Replace Brake Pads Without Special Tools: A Complete DIY Guide
- Why New Brake Pads Squeak After Replacement: Complete Guide to Causes and Solutions
- Ceramic vs Organic Brake Pads: The Ultimate Guide to Choosing the Right Brakes for Your Vehicle
- Best Ceramic Brake Pads for BMW: Complete 2025 Performance Guide