Most people understand the main components of a vehicle’s braking system. You have the master cylinder, lines, rotors (or drums), brake pads (or shoes), brake booster, and pedal.
But one small component plays a major role when it comes to brake noise. Here’s everything you want to know about brake pad shims which are sometimes referred to as anti-squeal shims.
What are Brake Shims?
Simply put, the main function of brake pad shims is to prevent brake noise. At each corner of a vehicle, brake pads and brake rotors (or drums) sit very close to each other. The only thing that stops them from clanging together is the brake shim.
The brake pad shim is a component which goes in between the calipers and pads to prevent friction from occurring. Basically, the shims keep them aligned with each other, so they can function without generating noise.
These anti-squeal shims are either adhesive or non-adhesive pads made of either rubber or metal. They go in between the middle of the brake calipers and brake pads.
If a brake shim were to become damaged or removed, then too many imperfections would exist between the rotors and pads. This would cause them to clang together and make strange noises. You will hear these noises each time you step on the brake pedal.
Can You Install Brake Pads Without Shims?
Yes, you can install brake pads without shims, although shims are generally recommended. Shims serve to reduce noise and vibration, but they do not affect the performance of the brake pads themselves.
For example, a discussion on Honda-Tech mentions that shims are just there to reduce noise and vibration and do not affect performance. However, it’s important to note that while you can run without shims, they do help in preventing squealing and allow for quieter operation.
Is Brake Pad Grease Necessary?
If you have brake shims installed between your brake calipers and brake pads, there may still be instances when you hear noises coming from your braking system. Again, this doesn’t necessarily mean that your brake rotors are to blame.
Usually, these noises occur because your brake shims are not lubricated enough grease or some other formulated lubricant. This will assist the shims in aligning the caliper and pads properly while reducing friction.
Just apply a thin film of grease to each shim if they have not already been lubricated. Never apply grease to the front of the brake pads!
Why Do Some Brake Pads Have Shims?
A lot of newer brake pads come with the shims already attached to them. So, if you are trying to replace your brake parts, there are brake kits available which contain both the pads and shims together.
In other kits, the shims will be separate from the pads and they will include adhesive backings that let you attach the shims to the pads. If you are new to brake pad shim installation, then you should purchase the brake pads which have the shims already attached.
Types of Brake Pad Shims
There are a few main types of brake pad shims that serve slightly different functions:
Rubber Shims
Rubber shims are very common and placed between the brake pad and brake caliper piston. They are made of flexible rubber or rubberized synthetics.
The natural flexibility of the rubber helps to insulate the pad from vibrations and noise that would otherwise emit from the metal components rubbing together. Rubber shims range in thickness, but typically come in around 0.5 mm to 2 mm thick.
Metal Shims
Metal shims also go between the brake pad and piston. However, these are made of thin sheets of steel or aluminum, making them stiffer than the rubber variety. Metal shims can be coated or uncoated.
The thickness and coatings applied to metal shims affects their insulating capabilities. Thicker shims around 1.5 mm dampen more noise and vibration. Coated shims also help to reduce friction between the metal parts. Different vehicles call for specific configurations to tune the braking performance.
Insulating Shims
Finally, there are insulation shims that attach to the brake pad backing plate itself. These help dampen vibrations emitting from the pad surface by adding mass.
Insulating shims come in materials like fiberglass or rubberized synthetics around 3-5 mm thick. Some high performance pads have them integrated into the backing plate.
Can You Reuse Brake Pad Shims?
In most cases, yes, you can reuse old shims as long as they are in good condition. You’ll want to clean them off with a little bit of brake cleaner and a rag or paper towels before attaching them to the new pads.
Symptoms of Bad or Missing Brake Shims
There may come a day when your brake shims end up wearing out or deteriorating from excessive use. Once that happens, you will notice some strange symptoms occur. In case your brake pads are missing shims, the same symptoms will apply.
#1 – Brake Noise
The main symptom, of course, will be a lot of loud squealing or squeaking noises coming from your brakes each time you step on the brake pedal. If you recently installed new brake pads and you’re getting squealing noise whenever you are braking, double-check to make sure you’re not missing the shims.
#2 – Pulsating Brake Pedal
You may also notice a pulsating brake pedal anytime you press your foot up against it. This is because faulty or missing brake shims are causing misalignment between the pads and calipers.
See Also: Why Does My Brake Pedal Go to the Floor?
#3 – Poor Braking Response
The worst-case scenario will be a limited brake response, but that should only happen if your brake pads are not able to sufficiently access the brake rotors. This is due to the brake pads not being properly aligned with the brake calipers.
Because of this, the brake pads cannot adequately interact with the brake rotors to slow down the vehicle in time. On top of that, this can also wear out your brake pads and calipers quicker than normal.
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can we reuse brake shims from old pads? coz some article says you cannot reuse brake shims
As long as the shims are removable it should be fine. The purpose of shims is to help reduce braking noise and vibration. Some pads (especially performance pads) don’t even come with them.
I have install discs and brakes on all 4 corners and had to fit 2 sets of pads and 3 sets of shims. This is due to a clicking on just one brake, but still it is clicking. I give up as it has cost me a lit of time and money.
Could you tell me what is the problem please
Make sure you’re using brake parts lubricant on the brake hardware, including the shims. This may cut down on noise. When you do this, do not put lubricant of any kind of the pad material or rotors.
If it still clicks, there may be a mechanical problem with the caliper. A local shop should be able to help you diagnose the problem.
Ive been telling this to people for years,I’m gonna be 50 next week,been working on cars since i was 11, about how when you do a brake job you MUST put grease on your pads,obviously not on the surface that contacts the rotor but on the area where it rests in the corners of the caliper bracket and on the back of the pad,the area that contacts the caliper and pistons.
When you buy a set of cheap 20 dollar pads or a 100 dollar ceramic pads top of the line and you install them properly with grease only one thing will happen, you will have dust or you wont and thats it, i get a chuckle when i hear people say “buy the high dollar ones,those dont squeal” ha ha ha.
If you are low on the dinero buy you some intermediate pads,those usually are real nice but always use your brake grease, usually at your neighborhood part store at the counter they will have a little rack with all kinds of little bags with stuff like brake grease, dielectric grease for your spark plug boots and so forth, that stuff is not there for looks, it works and its cheap, usually a 99 cent little bag will do a set of front or rear brakes if you squeeze it hard enough.
In my lifetime i have probably done 100 plus brake jobs and i haven’t had a single person call me irate because the Brakes are squealing, not a single time, remember G-R-E-A-S-E everytime you do your brake job,you will be glad you did and your significant other will think your a magician because you got rid of that squeal,lol,
Brake grease is called that because its special, you can’t use that grease that you cooked your bacon on last night,brakes work with friction,they get incredibly hot so this grease is made to withstand high temperatures without melting and running out so buy the right thing and be safe when you do your brake job, take care.
Carlos, I agree. In fact, sometimes high dollar pads are even more likely to squeal if you’re shopping for track pads, for instance. I grease the back of my pads and the parts that contact the caliper hardware and have never had an issue with excessive brake noise.
You’ve been working on cars since age 11 and you have only done 100 brake jobs?
Although it is not so common these days, over the past 40 years many people have worked on their own cars, buying the parts at a nearby auto parts store. Listening to good advice, doing it yourself a few times, enjoy the wonderful feeling of freedom, and control over your own money!
When a person starts to struggle from his own heart, he is a valuable person
Well explained,thank you,as have had a banging coming from all wheels only since I had the brakes done no noise before,a friend had same problem and he got his brakes done at same garage,he went elsewhere to be told the shims had been replaced,garage sorted this,took no money from my friend and banging noise was gone so I was checking out what shims were and you explained it spot on,thank you