{"id":1679,"date":"2026-10-10T01:03:53","date_gmt":"2026-10-09T17:03:53","guid":{"rendered":"https:\/\/topbrakeparts.com\/?p=1679"},"modified":"2026-10-29T11:09:53","modified_gmt":"2026-10-29T03:09:53","slug":"remblokvullings","status":"publish","type":"post","link":"https:\/\/topbrakeparts.com\/af\/brake-pad-shims\/","title":{"rendered":"Wat doen remblokvullings? Tipes, materiale & hoe hulle geraas verminder"},"content":{"rendered":"

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Brake pad shims are thin layers of steel, rubber or multi-layer composite fitted to the back of a disc brake pad, between the backing plate and the caliper piston or fingers. They look like a minor detail, but they decide a large part of how quietly a brake works. A pad with the right friction material and the wrong shim can still squeal; a pad with a well-designed, well-fitted shim often stays quiet on the same car.<\/p>\n

This guide explains what brake shims do, how they control vibration, which shim types and materials are used, what goes wrong when a shim is damaged or missing, and how repair shops and parts buyers should check them. It is written for auto parts stores and repair shops that sell, fit and warranty brake pads every day, so each section ends with practical checks rather than theory alone.<\/p>\n

We fit and inspect shims on our own pad lines in Guangdong, and the inspection and test results in this article come from that work.<\/p>\n

Brake Pad Shims: Quick Reference<\/strong><\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n
Question<\/th>\nShort answer<\/th>\n<\/tr>\n<\/thead>\n
What is a brake pad shim?<\/td>\nA thin damping layer on the back of the pad, between the backing plate and the caliper<\/td>\n<\/tr>\n
What does it do?<\/td>\nDamps vibration, helps control squeal, spreads piston load and slows heat transfer into the caliper<\/td>\n<\/tr>\n
Is it part of the friction material?<\/td>\nNo. It sits on the non-friction side and never touches the rotor<\/td>\n<\/tr>\n
Main types<\/td>\nSingle-layer steel, multi-layer steel, rubber-coated, bonded and clip-on shims<\/td>\n<\/tr>\n
Most common failure<\/td>\nLoose, delaminated, missing or wrong-type shims<\/td>\n<\/tr>\n
Do all pads need one?<\/td>\nMost passenger-car pads use a shim or an equivalent NVH design; the correct choice follows the OE design<\/td>\n<\/tr>\n
Who should check it?<\/td>\nThe technician at installation and the buyer at sample approval<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n
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01<\/span><\/p>\n

What Is a Brake Pad Shim?<\/h2>\n<\/div>\n

What is a brake pad shim in practical terms? It is the thin plate on the back of a disc brake pad that separates the pad from the parts that push on it. When people ask what are brake shims, or what are shims on brake pads, they usually mean this layer\u2014not the shims used in engines, door hinges or drum brakes. And if a customer at the counter asks what are shims for brakes, the one-line answer is: to keep the pad quiet and stable in the caliper.<\/p>\n

A shim is part of the pad assembly, along with the steel backing plate, the friction block, chamfers and slots, and any wear indicator.<\/p>\n

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If you need a refresher on how those parts work together, our guide to brake pads<\/a> covers construction, materials and identification in detail.<\/p>\n<\/div>\n

<\/div>\n

Where Is the Shim Located on a Brake Pad?<\/h3>\n

The shim sits on the back of the backing plate\u2014the side that faces the caliper piston on the inner pad and the caliper fingers or housing on the outer pad. On most pads it covers the central area of the plate where the piston or fingers apply force. It does not extend onto the abutment ears that slide in the caliper bracket, and it must never overhang the plate edges.<\/p>\n

On some designs the inner and outer pads carry different shims, because the piston contact area and the finger contact area have different shapes. That is one reason inner and outer pads are not always interchangeable.<\/p>\n

<\/div>\n

What Is the Main Purpose of a Brake Pad Shim?<\/h3>\n

The main purpose is noise control. Brakes squeal when the pad, rotor and caliper vibrate together at an audible frequency. A shim adds damping and a break in the vibration path, so less energy reaches the caliper and less noise reaches the driver. Secondary jobs include spreading piston load more evenly across the backing plate and slowing heat transfer from the pad into the piston.<\/p>\n

<\/div>\n

Are Brake Pad Shims Part of the Friction Material?<\/h3>\n

No. The friction material is the working layer that rubs on the rotor. The shim is on the opposite side of the backing plate and never contacts the rotor. That matters when diagnosing noise: a squeal can come from the friction interface, from the shim interface, or from both, and the fixes are different.<\/p>\n

\n\n\n\n\n\n\n\n\n\n
Pad component<\/th>\nLocation<\/th>\nMain job<\/th>\nTouches rotor?<\/th>\n<\/tr>\n<\/thead>\n
Friction material<\/td>\nFront face<\/td>\nCreates braking friction<\/td>\nYes<\/td>\n<\/tr>\n
Backing plate<\/td>\nMiddle<\/td>\nCarries load, locates pad in bracket<\/td>\nNo<\/td>\n<\/tr>\n
Shim<\/td>\nBack of backing plate<\/td>\nDamps vibration, spreads load, insulates<\/td>\nNo<\/td>\n<\/tr>\n
Chamfers and slots<\/td>\nFriction face<\/td>\nShape contact and vibration modes<\/td>\nYes (edges)<\/td>\n<\/tr>\n
Wear indicator<\/td>\nPlate edge or sensor clip<\/td>\nWarns when pad is worn<\/td>\nOnly when worn<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n
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02<\/span><\/p>\n

What Do Brake Pad Shims Actually Do?<\/h2>\n<\/div>\n

Brake pads and shims work as one assembly. The shim does four jobs, and each one affects how the brake feels and sounds.<\/p>\n

<\/div>\n

Reduce Vibration Between the Pad and Caliper<\/h3>\n

During braking the pad is never perfectly still. Small friction-induced vibrations travel from the rubbing surface through the backing plate. Without a shim, the backing plate sits steel-on-steel against the piston and caliper fingers, and that vibration passes straight into the caliper body, which can act like a speaker. A shim interrupts that path and absorbs part of the energy before it gets there.<\/p>\n

<\/div>\n

Help Control Brake Squeal<\/h3>\n

Most brake squeal is a high-frequency tone created when pad and rotor vibrations lock together. Anti squeal shims are designed to make that harder to happen: the damping layer reduces the vibration amplitude, and the change in contact stiffness can move the system away from the frequencies where squeal builds. Shims are one of the most effective noise-control parts in the corner, but they work together with the rotor, the pad geometry and the caliper hardware\u2014our guide to the five most common causes of brake squeal<\/a> explains how those pieces interact.<\/p>\n

<\/div>\n

Improve Contact Between the Pad and Caliper<\/h3>\n

The piston pushes on a small ring of the backing plate, and the caliper fingers push on two narrow areas. A flat, well-bonded shim helps distribute that force across a wider area of the plate. More even load keeps the friction face in more even contact with the rotor, which helps both noise and wear.<\/p>\n

<\/div>\n

Help Isolate Heat and Vibration<\/h3>\n

Rubber-coated and multi-layer shims also slow the transfer of heat from the pad into the caliper piston and brake fluid. The effect is modest on everyday driving, but on heavy vehicles and during repeated hard stops it helps keep piston seals and fluid cooler. Performance shims made from titanium or with special insulating layers push this function further.<\/p>\n

\n\n\n\n\n\n\n\n\n
Function<\/th>\nHow the shim does it<\/th>\nWhat the driver notices<\/th>\n<\/tr>\n<\/thead>\n
Vibration damping<\/td>\nViscoelastic layer absorbs vibration energy<\/td>\nLess squeal and chatter<\/td>\n<\/tr>\n
Squeal control<\/td>\nChanges stiffness and breaks the vibration path<\/td>\nQuieter light braking<\/td>\n<\/tr>\n
Load distribution<\/td>\nSpreads piston and finger force<\/td>\nMore even pad wear and feel<\/td>\n<\/tr>\n
Heat isolation<\/td>\nInsulating layer between plate and piston<\/td>\nMore stable pedal under repeated stops<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n
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03<\/span><\/p>\n

How Do Brake Pad Shims Reduce Brake Noise?<\/h2>\n<\/div>\n

To understand how shims reduce noise, it helps to know how noise is measured.<\/p>\n

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The 70 dB(A) Threshold Behind Squeal Tests<\/p>\n

SAE J2521<\/a> defines brake squeal during dynamometer testing as a peak noise level of at least 70 dB(A), typically within 1.25\u201316 kHz when a full suspension corner or axle assembly is tested.<\/p>\n

For brake assemblies tested without the complete suspension corner, the evaluated frequency range is 2\u201316 kHz.<\/p>\n

Source: SAE International, SAE J2521_202210 \u2013 Inertia Dynamometer Brake Squeal Noise Test Procedure.<\/p>\n<\/div>\n

In other words, squeal is a measurable event: a sound above a set loudness inside a defined frequency band. Shim design is judged by how many of those events it removes across a test matrix of pressures, speeds and temperatures\u2014not by whether one stop sounds quiet.<\/p>\n

\"Brake
Shim designs are judged by how many squeal events they remove on an nvh dynamometer<\/figcaption><\/figure>\n
<\/div>\n

How Brake Vibration Creates Squeal<\/h3>\n
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Three things combine to create squeal<\/p>\n

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  1. An excitation source:<\/strong> friction at the pad\u2013rotor interface varies slightly as the rotor turns, especially at low speed and light pressure.<\/li>\n
  2. A resonant structure:<\/strong> the rotor, pad and caliper each have natural frequencies. When friction couples two of them, the vibration can grow instead of fading.<\/li>\n
  3. A radiating surface:<\/strong> the rotor face and caliper body turn the vibration into sound waves.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n

    Remove or weaken any one of the three and the squeal becomes less likely. Friction material and rotor finish work mainly on the first; chamfers and slots on the second; the shim works on the second and third by adding damping and blocking the path into the caliper.<\/p>\n

    <\/div>\n

    How a Shim Changes Vibration Transmission<\/h3>\n

    A multi-layer shim works like a small damper. Two thin steel layers are separated by a viscoelastic adhesive or rubber layer. When the backing plate vibrates, the steel layers move slightly relative to each other and the middle layer is sheared. That shearing turns vibration energy into a very small amount of heat. A rubber-coated shim works in a similar way, with the elastomer layer providing the damping. Fit matters as much as material: a shim that is loose or only partly bonded cannot shear its damping layer properly and loses much of its effect. One 2024 project put numbers on this: a tighter shim plus a chamfer opened from 1.0 mm to 1.5 mm dropped the squeal rate from 6 stops in 10 to 1 in 10 (full diagnosis<\/a>).<\/p>\n

    <\/div>\n

    Why Shim Design Alone Cannot Eliminate All Brake Noise<\/h3>\n

    A shim reduces noise; it does not cancel every cause. A glazed or out-of-runout rotor, contaminated pads, a sticking slide pin or worn abutment clips can all produce noise that no shim will fix. Low-frequency groan, grinding from a worn pad, or the scraping squeal of a mechanical wear indicator are different problems altogether.<\/p>\n

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    The Shim Is One Noise Control, Not the Only One<\/p>\n

    Treat the shim as one of several noise controls. When a pad squeals, check the shim, then the rotor, then the hardware, then the bedding\u2014rather than swapping shims repeatedly.<\/p>\n<\/div>\n<\/section>\n

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    04<\/span><\/p>\n

    What Types of Brake Pad Shims Are Commonly Used?<\/h2>\n<\/div>\n

    Brake shims fall into five practical types. Some are defined by construction (single or multi-layer), others by how they attach to the pad (bonded or clip-on). Most real shims combine one construction with one attachment method\u2014for example, a multi-layer rubber-coated shim that is bonded to the plate.<\/p>\n

    <\/div>\n

    Single-Layer Steel Shims<\/h3>\n

    A single, thin steel plate, sometimes with a light coating. It separates the backing plate from the piston and spreads load, but offers limited damping. Single-layer shims are common on low-cost pads and on applications that are not noise-sensitive.<\/p>\n

    <\/div>\n

    Multi-Layer Steel Shims<\/h3>\n

    Two or more thin steel layers with a damping layer between them, known as constrained-layer damping. They give the best vibration absorption of the common types and are widely used on OE pads for noise-sensitive passenger cars and SUVs.<\/p>\n

    <\/div>\n

    Rubber-Coated Shims<\/h3>\n

    A steel core coated with rubber or another elastomer on one or both sides. The rubber adds damping and grip, and helps the shim seat evenly against the piston or caliper fingers. Rubber-coated steel is one of the most common aftermarket choices.<\/p>\n

    <\/div>\n

    Adhesive or Bonded Shims<\/h3>\n

    Shims attached to the backing plate with a pressure-sensitive or heat-cured adhesive. Bonding keeps the shim in close contact across its whole area, which is good for damping. The risk is the bond line: heat cycles, poor surface preparation or the wrong adhesive can lead to peeling or delamination.<\/p>\n

    <\/div>\n

    Clip-On or Mechanically Attached Shims<\/h3>\n

    Shims held by tabs, fingers or rivets that hook over the backing plate. They resist shear and are less likely to peel under heat, and some designs allow the shim to “float” slightly so the pad can move without tearing the attachment. They depend on correct tab design and plate dimensions; a clip that does not lock firmly can rattle.<\/p>\n

    \n\n\n\n\n\n\n\n\n\n
    Shim type<\/th>\nDamping level<\/th>\nAttachment risk<\/th>\nTypical use<\/th>\nBuyer question<\/th>\n<\/tr>\n<\/thead>\n
    Single-layer steel<\/td>\nLow<\/td>\nLow<\/td>\nBudget and low-sensitivity applications<\/td>\nIs the OE pad also single-layer?<\/td>\n<\/tr>\n
    Multi-layer steel<\/td>\nHigh<\/td>\nMedium (layer bond)<\/td>\nNoise-sensitive cars and SUVs<\/td>\nHow many layers, and what damping layer?<\/td>\n<\/tr>\n
    Rubber-coated<\/td>\nMedium\u2013high<\/td>\nMedium<\/td>\nMainstream aftermarket<\/td>\nOne- or two-side coating?<\/td>\n<\/tr>\n
    Bonded<\/td>\nDepends on shim<\/td>\nBond line<\/td>\nMost OE-style pads<\/td>\nAdhesive type and peel\/shear test?<\/td>\n<\/tr>\n
    Clip-on \/ mechanical<\/td>\nDepends on shim<\/td>\nTab fit<\/td>\nHeat-exposed or shear-prone designs<\/td>\nDoes the clip lock without play?<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n
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    05<\/span><\/p>\n

    What Materials Are Brake Pad Shims Made From?<\/h2>\n<\/div>\n

    Shim material decides corrosion resistance, damping and heat behavior. Most brake pad shims combine at least two of the materials below.<\/p>\n

    \"Salt
    Salt spray testing shows whether plate and shim coatings will hold up in salt-belt markets<\/figcaption><\/figure>\n
    <\/div>\n

    Steel<\/h3>\n

    Cold-rolled carbon steel is the base of most shims because it is stiff, thin, easy to stamp and inexpensive. It needs a coating or plating to resist corrosion, especially in markets that use road salt.<\/p>\n

    <\/div>\n

    Stainless Steel<\/h3>\n

    Stainless steel resists rust without heavy coatings and keeps its surface condition in wet and salty conditions. It is common for shim layers that face the piston and on premium or heavy-duty pads. High-performance and racing pads sometimes use titanium shims for the same reason plus better heat insulation, but titanium is a niche choice because of cost.<\/p>\n

    <\/div>\n

    Rubber and Elastomer Coatings<\/h3>\n

    Nitrile rubber and other elastomers provide damping and a slightly compliant contact surface. Their key properties are temperature resistance and adhesion to the steel layer; a coating that softens, cracks or separates at high temperature loses its damping function.<\/p>\n

    <\/div>\n

    Multi-Layer Composite Materials<\/h3>\n

    Composite shims stack steel, stainless steel, rubber and viscoelastic adhesive in a defined order. The layer sequence and thickness are tuned to the frequencies that matter on a given application, which is why an OE multi-layer shim cannot always be replaced by a generic one with the same outline.<\/p>\n

    \n\n\n\n\n\n\n\n\n\n
    Material<\/th>\nStrength<\/th>\nLimitation<\/th>\nWhat to specify<\/th>\n<\/tr>\n<\/thead>\n
    Carbon steel<\/td>\nStiff, low cost, easy to form<\/td>\nNeeds corrosion protection<\/td>\nPlating or coating type, salt spray hours<\/td>\n<\/tr>\n
    Stainless steel<\/td>\nCorrosion resistant<\/td>\nHigher cost<\/td>\nGrade, surface finish<\/td>\n<\/tr>\n
    Rubber \/ elastomer coating<\/td>\nDamping, compliant contact<\/td>\nTemperature limit, adhesion<\/td>\nCoating type, temperature rating, adhesion test<\/td>\n<\/tr>\n
    Multi-layer composite<\/td>\nHighest damping<\/td>\nLayer bond, cost<\/td>\nLayer structure, total thickness, damping layer<\/td>\n<\/tr>\n
    Titanium (performance)<\/td>\nHeat insulation, corrosion resistance<\/td>\nCost<\/td>\nUse only where heat is the main issue<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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    Describing a Shim as a Material System<\/p>\n

    Describe the shim as a material system, not one word. For example: “Two-layer shim: stainless steel outer layer, carbon steel inner layer with rubber coating both sides; total thickness [X] mm \u00b1 [Y] mm; coating rated to [Z] \u00b0C; salt spray resistance [N] hours.”<\/p>\n<\/div>\n<\/section>\n

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    06<\/span><\/p>\n

    What Happens When Brake Pad Shims Are Damaged or Incorrectly Fitted?<\/h2>\n<\/div>\n

    A shim that is damaged or fitted the wrong way stops doing its job, and in some cases becomes a noise source itself.<\/p>\n

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    Why NUCAP Lets the Shim Float<\/p>\n

    NUCAP’s technical documentation<\/a> notes that brake-pad movement can place high shear stress on a shim attachment, with the caliper piston applying up to about 1,000 ft-lb of force in the example described.<\/p>\n

    Repeated movement can damage the attachment or contribute to shim delamination, which is why attachment design and fit matter in addition to shim material itself.<\/p>\n

    Source: NUCAP Industries, NU-LOK Independent Floating Shim Technology.<\/p>\n<\/div>\n

    <\/div>\n

    Loose or Misaligned Shims<\/h3>\n

    A shim that has shifted, lifted at one edge or was installed off-center no longer covers the piston and finger contact areas. Damping drops, and the loose edge can buzz or rattle against the caliper. Misalignment is common when clip-on shims are refitted by hand or when a bonded shim slides before its adhesive cures.<\/p>\n

    <\/div>\n

    Damaged or Delaminated Shim Layers<\/h3>\n

    Heat, shear and corrosion can separate the layers of a multi-layer shim or peel the rubber coating. Signs include bubbling, flaking rubber, a visible gap between layers, or a shim that feels soft or crunchy when pressed. A delaminated shim has lost most of its damping, even if it still looks attached.<\/p>\n

    <\/div>\n

    Missing Shims<\/h3>\n

    Shims can be missing because the pad was supplied without one, because a loose OE-style shim was left on the bench, or because it fell off during handling. Without the shim, steel contacts steel at the piston and fingers, and noise is much more likely. Heat transfer into the piston also increases.<\/p>\n

    <\/div>\n

    Incorrect Shim Shape or Thickness<\/h3>\n

    A shim that is too thick can make the pad assembly tight in the caliper or reduce piston retraction clearance, causing drag. A shim that is too thin, too small or the wrong shape leaves part of the contact area uncovered. An outline that overhangs the plate can foul the bracket or caliper.<\/p>\n

    <\/div>\n

    Contamination Between the Shim and Backing Plate<\/h3>\n

    Oil, rust, paint overspray or dust on the backing plate before bonding prevents the adhesive from wetting the surface. The shim may look fine on a new pad and then peel after the first heat cycles. Brake grease applied under a bonded shim during installation has the same effect. Backing-plate surface preparation and flatness are the foundation of shim adhesion; we plan to cover them in a separate guide to brake pad backing plates.<\/p>\n

    \"Brake
    A clean, flat backing plate is the foundation of shim adhesion<\/figcaption><\/figure>\n
    \n\n\n\n\n\n\n\n\n\n
    Fault<\/th>\nTypical cause<\/th>\nSymptom<\/th>\nAction<\/th>\n<\/tr>\n<\/thead>\n
    Loose or misaligned<\/td>\nPoor bonding, handling, wrong fitting<\/td>\nSqueal, buzzing, rattle<\/td>\nReplace pad set or correctly fit new shim<\/td>\n<\/tr>\n
    Delaminated layers<\/td>\nHeat, shear, corrosion<\/td>\nSqueal returns after weeks<\/td>\nReplace pad set<\/td>\n<\/tr>\n
    Missing<\/td>\nSupply or installation error<\/td>\nSqueal, harsher feel<\/td>\nFit pads with correct shims<\/td>\n<\/tr>\n
    Wrong shape or thickness<\/td>\nGeneric shim on specific application<\/td>\nNoise, drag, tight fit<\/td>\nChange to OE-matched design<\/td>\n<\/tr>\n
    Contaminated bond line<\/td>\nDirty plate, grease under shim<\/td>\nShim peels after heat cycles<\/td>\nReject batch; check plate preparation<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n
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    07<\/span><\/p>\n

    Can Bad Brake Pad Shims Cause Brake Squeal?<\/h2>\n<\/div>\n

    Yes. A failed brake pad shim is one of the most common reasons a pad that was quiet when new starts to squeal, and one of the most common reasons a new pad squeals from the first drive.<\/p>\n

    <\/div>\n

    Common Noise Symptoms Linked to Shim Problems<\/h3>\n

    Worn or failed brake shims rarely announce themselves visually while the wheel is on, so the noise pattern is the first clue. Listen for when it happens and from which corner before taking anything apart:<\/p>\n