When you brake, brake pads create friction by pressing against spinning rotors. That friction is necessary. Typically, whether you are using normal or ceramic brake pads, you would want all of the brake pads to have even wear on both sides.
There are circumstances where each side of the brake pad wears down unevenly and you are forced to replace all the brake pads sooner than you anticipated.
To prevent that costly expense in the future, it is important to find the reason for the uneven wear on the brake pads before it happens again.
7 Main Reasons Why Your Brake Pads Wear Unevenly
Here are the most common reasons brake pads wear out faster on one side of the vehicle.
#1. Rotor Thickness Variation.
Disc thickness variation refers to when your rotors are different thicknesses, which can cause the brake pads to wear differently between the two rotors.
Your rotors will have a greater number of flat spots that your brake pads will touch, and once they do, the brakes will wear unevenly on that side.
#2. Sticking Caliper Pistons.
If you have some debris or rust on one or more of the pistons, it can cause sticking brake calipers. This can mean the piston won’t slide correctly, causing the brake pad to touch the rotor constantly.
A sticking brake caliper makes the brake pad material disappear quicker than the others.
#3. Mis-alignment.
Sometimes, when the mechanic installs new brake pads, they may not be installed correctly or evenly, sometimes because the bracket on the back of the pad is bent.
If you have brake pads that are misaligned, they wear unevenly based on your braking activities.
You should notice the problem within a few days of having new misaligned brake pads. When you start experiencing braking issues, you will wonder how your brake pads can be acting up already after just being installed.
Well, it’s because your brake pads are being worn unevenly. After all, they are not aligned properly in the caliper.
#4. Dirty or Rusty Rotors.
Dirty rotors can certainly cause uneven wear on your brake pads. Dirt and grime can affect the surface and texture of your rotors, dirty rotors don’t have to be old rotors either.
Brand new rotors do have some unique circumstances. While not a common occurrence, some vehicles are new, while many are used in their life, you may still have grease or dirt on the surface of the rotor from the installation process.
Anyone, from an auto tech to a DIYer, shouldn’t forget that light debris should always be cleaned off; it’s often things like brake cleaner or some formulation of brake cleaner.
When you purchase a new rotor, there is often a gray paint-like or oily protective coating to protect it from rust. It is okay to use a brake cleaner to remove it, but you don’t absolutely have to. If you brake normally, that coating will be removed as the pad contacts the rotor surface.
#5. Warped Rotors.
A warped rotor can mean the surface line of the rotor isn’t a perfectly smooth circle but slightly deformed or somewhat wave-like. Generally, you get a slightly deformed rotor when cold water comes into contact with a hot rotor.
If you have a warped rotor, your brake pad is only contacting the high points on the rotor, whereas other brake pads are making contact on the entire surface of the rotor.
This is why it is very important to never immediately spray water on any of your wheels and start washing your car right away if you are driving around spiritedly. You should let the rotors cool enough so that when you touch them, they feel warm to the touch and not hot.
If you ever want to check it out and confirm this, simply place your hand a few inches away from the rotor. If it is really hot, you will feel the heat in the air, so just wait a few minutes before adding water.
#6. Corroded or Seized Guide Pins.
Another thing is, corroded or seized guide pins. These pins aid the caliper to slide and compress the brake pads against the rotor.
If there’s enough build-up of debris or moisture, they will corrode, which can stop the caliper from moving at all, which can lead to uneven wear on your brake pads.
The solution is simple, but you should clean and lubricate your caliper guide pins on a regular basis to protect against rust, decrease friction, and keep the brake pads in good shape.
#7. Different Types of Brake Pads.
It is important to be consistent in the type of brake pads you install in your braking system.
Don’t mix and match different types of brake pads, let alone different brands, products, or composite materials, because they will likely wear down very differently and have completely different life spans.
If you use the same composition, model, and thickness for your brake pads, you will have a much higher chance that they will wear evenly.
Avoiding Uneven Brake Pad Wear
Brake Inspection
The best thing you can do to ensure optimal brake performance, while avoiding uneven brake pad wear, is to have regular brake service appointments scheduled through a trusted mechanic.
Regular inspections of brake pads, brake lines, brake calipers, etc., are the best way to catch any identified problems early on and to help with the balance of stopping power at those front and rear brakes.
Brake Pad Installation
With brake pads, it is critical that, during a brake pad replacement, the mechanic properly installs and aligns the new brake pads.
As an example, if the brackets are bent or not flush to the brake pads, this can result in an uneven amount of wear on your brake pads, therefore potentially compromising all functions of your brake system.
In the event you have decided to attempt brake pad replacements instead of using a trusted mechanic, just ensure you follow the proper procedure and take ample time during the installation process.
Brake Component Maintenance
Maintaining the other components of your brake system, such as cleaning and lubricating the slide pins or replacing worn-out caliper pin boots, can help reduce uneven wear.
If you invested some time regularly maintaining all those components, it would avoid cost down the road by extending the life of your brake pads and other brake system components.
Diagnosing Unequal Brake Pad Wear
Assess Brake Pad Wear Patterns
When it comes to diagnosing equal brake pad wear, you want to look for a wedge or taper when inspecting the pads, indicating potential quality or installation issues.
There is one other factor to examine with brake pad wear, and that is the difference in wear for the inner compared to the outer pads. If the outer pads are considerably more worn than the inner pads, there may be guide pin issues.
Evaluate Rotor Thickness Variation
Once you have assessed brake pad wear patterns, inspect for rotor (disc) thickness variation (DTV). DTV is the difference in rotor thickness at different points of contact due to uneven wear. High amounts of DTV can cause brake judder or pulsation.
To check rotor thickness, measure with a micrometer at several points around the circumference of the rotor to determine if they are within the allowable limit. If you don’t have the capacity to do this yourself, any brake shop will be able to do this for you.
Look for Residual Brake Pressure
Check for possible residual brake fluid pressure, which may cause the pistons to stick, therefore causing uneven wear between brake pads.
You should bleed the brakes and inspect the whole system for signs of residual pressure, if you don’t want the brakes to be uneven and perform optimally.
Repairing Uneven Wear of Brake Pads
Sometimes brakes might need some love to repair the brake pads that are wearing unevenly. If you replace the pads and don’t correct the cause of the problem, don’t be surprised if your new pads wear unevenly as well. Here’s what to do instead:
- First, you need to get underneath the vehicle to check the brake caliper and all its components. It is important to see if the caliper piston is working correctly and is not seized. If this is the case, replace the brake caliper or brake caliper piston.
- You must also check the guide pins, as they have a huge role in ensuring there is no uneven wear between brake pads. Properly lubricated slide pins ensure that your floating caliper will glide evenly. If you see that some slide pins have corroded or are damaged, replace them.
- You should also check the brake lines for wear and tear. If there is excess heat or obvious damage, the brake line should be replaced.
- Also, check the rotor thickness. The acceptable rotor thickness can be found in your repair manual or from a trusted mechanic. If the rotor is too thin, you’ll have to replace it, and the opposite rotor as well.
- While you’re doing these things, don’t forget to look at the brake pads! For best results, use high-quality brake pads that match your vehicle specifications.
Frequently Asked Questions.
Q: Why Are My Brake Pads Worn Diagonally?
Some common reasons for your brake pads to wear diagonally include damaged rotors putting uneven pressure on the pads, seized guide pins keeping the pads from retracting, a brake line not allowing fluid to flow back and forth, master cylinder issues pumping fluid, or a leaking or sticking caliper.
Q: Is It Dangerous to Drive with Uneven Brake Pad Wear?
Yes. Driving with uneven brake pad wear is dangerous as it can affect your vehicle’s braking performance.
Longer stops, more brake pedal effort, or less brake application, depending on how the pads wear, can mean a loss in performance that might lead to loss of control or a higher likelihood of vehicle accidents.
Q: What Are the Signs of Uneven Rotor Wear?
Some signs of uneven rotor wear are a brake pedal that pulsates or vibrates, a steering wheel that vibrates during braking, and/or inconsistent braking performance. Additionally, you may hear grinding or scraping noises when you apply your brakes.