Brake Pad Shims: Meaning, Types, Benefits, Usage
Brake pad shims are thin pieces of metal that go between the brake pad and brake caliper piston (source: https://honda-tech.com/forums/suspension-brakes-54/importance-brake-pad-shims-2113681/). The main purpose of brake pad shims is to reduce vibrations and noise caused by minor irregularities between the brake pad surface and caliper piston. They help evenly distribute braking force and prevent the pads from rocking or shifting during braking. This ensures smooth, consistent braking performance.
There are a few different types of brake pad shims:
- Rubber shims – Made of rubber or flexible polymer, these dampen vibrations
- Stainless steel shims – Rigid and durable stainless steel construction
- Coated shims – Steel shims with a friction-reducing coating to minimize noise
Shims are designed to match precisely to the make and model of vehicle. Having properly fitted shims is important for proper braking functionality.
Types of Brake Pad Shims
Brake pad shims serve different purposes and come in various types. The three main types of brake pad shims are:
Insulating Shims
Insulating shims, also called abutment clips, are thin pieces of material placed between the brake pad and caliper piston. As described by https://shop.advanceautoparts.com/find/volvo-brake-pad-shims.c5889, these shims help insulate the caliper from heat generated during braking. They prevent brake fade and allow the brakes to operate smoothly.
Dampening Shims
Dampening shims are thicker, softer shims usually made of rubber or flexible plastic. Their purpose is to dampen vibrations and noise from the brakes, improving pedal feel and drive comfort. According to https://shop.advanceautoparts.com/find/porsche-brake-pad-shims.c5889, premium dampening shims can significantly reduce brake squeal and chatter.
Anti-Rattle Shims
Anti-rattle shims are designed to remove excess clearances that cause the brake pads to vibrate or rattle inside the caliper. These snug-fitting shims eliminate brake noise and ensure consistent pad performance.
Benefits of Using Shims
Brake pad shims provide several important benefits for braking performance and longevity. The primary benefits of shims are to reduce brake noise, prevent premature wear, and improve overall brake performance.
Brake pad shims act as a buffer between the brake pad and caliper piston to dampen vibrations that cause brake squeal. Without shims, metal-to-metal contact between the pad backing plate and caliper pistons can generate annoying squeaking and squealing noises when braking (Advics, 2023). Shims absorb these vibrations and minimize brake noise.
In addition to reducing noise, shims also prevent premature wear of brake system components. The constant metal-to-metal contact that occurs without shims causes accelerated wear of the pad backing plate and caliper pistons. Shims prevent this direct contact to reduce component wear rates and extend the service life of pads and calipers.
Finally, shims can improve the performance of brakes by allowing pads to move more freely within the caliper assembly. Shims reduce binding and allow the pads to retract evenly for optimal braking effectiveness. Improper pad retraction can lead to brake fade, pulling, and other issues.
When to Use Shims
There are a few key times when it is recommended to use brake pad shims during brake service or repair:
When replacing brake pads – Anytime the brake pads are being replaced, it is a good idea to also replace the shims. Over time, the shims can become compressed or damaged. Replacing them ensures proper vibration dampening and noise reduction for the new pads.
When brake noise is present – If a vehicle is experiencing brake squeal, chatter, or other noises, installing shims is an effective solution for resolving this issue. The shims create a barrier and dampen vibrations that lead to noise.
When brakes are worn unevenly – If brake pad wear is uneven across the rotor, this can indicate the pads are not properly aligned or are moving around in the caliper bracket. Adding shims helps keep the pads stable and wearing evenly.
Most vehicle manufacturers recommend installing new shims anytime the brake pads are replaced. Check your vehicle owner’s manual or factory service manual for the specific recommendations. Shims are inexpensive brake parts that provide big benefits for noise reduction and smoother braking.
How to Install Brake Pad Shims
Installing brake pad shims is a relatively straightforward process, though proper positioning and securing the shims is important for optimal performance.
Here is a step-by-step process for installing brake pad shims:
- Remove the old brake pads and thoroughly clean the caliper bracket where the new pads will be installed. Make sure there is no dirt, debris or rust present.
- Examine the new brake pads to determine where the shims need to be positioned. There will typically be a designated spot on the backing plate of the pad.
- Remove the adhesive backing from the brake pad shim and stick it to the proper location on the backing plate. Apply firm pressure to ensure it is securely adhered. Do this for all new pads that require shims.
- Install the new brake pads per the manufacturer instructions, being sure to align them properly in the caliper bracket.
- Re-assemble the caliper and wheel. Pump the brakes to seat the new pads before driving.
The key things to remember are to position the shim exactly where intended by the pad manufacturer, remove any adhesive backings, and firmly adhere the shims to the backing plates. Taking the time to properly install the shims will allow for quieter braking and optimal brake pad life.
Source: https://www.tonykartaustralia.com.au/how-to
Maintaining Shims
Properly maintaining brake pad shims is an important part of regular brake service and maintenance. Here are some key steps to keep in mind:
During brake service, inspect the condition of the shims. Look for signs of wear, corrosion, or damage. Shims that are bent, cracked, or have sections missing need to be replaced [1]. Worn or damaged shims can lead to brake noise, uneven pad wear, and reduced braking performance.
Replace shims at every brake pad change or whenever they show wear. Don’t reuse old shims. Over time, the adhesive wears out, allowing shims to slip. New shims ensure proper damping and anti-vibration between the brake pad and caliper.
Clean shims before installing new pads. Use brake cleaner to remove dirt, oil, and old adhesive. This allows fresh adhesive on the new brake pads to adhere properly. You can also lightly sand shims to prep the surface.
Lubricating shims with high temperature brake lubricant can help reduce corrosion and squeaking. Avoid getting lubricant on the rotor and brake pad surfaces. Apply lubricant sparingly to the shims as needed.
With proper shim inspection, replacement, cleaning, and lubrication, you can keep your brakes quiet and ensure maximum performance.
Signs of Worn Shims
There are a few key signs that indicate your brake pad shims need replacing:
Increased brake noise – As shims wear out, they lose their ability to dampen vibrations between the brake pad and caliper. This leads to brake squeal, squeaking and other noises when braking.
Uneven pad wear – Over time, worn shims allow the brake pad to shift slightly in the caliper bracket. This uneven contact can accelerate pad wear on one side.
Brake pulsation – If the pads vibrate excessively, it can cause deformation of the rotor over time. This can lead to a pulsating brake pedal feeling when braking.
Regular brake inspections will reveal any cracks, deformation or excessive corrosion on the shims. Replacing worn shims reduces noise, extends pad life and prevents expensive brake repairs down the road.
Sources:
https://www.advicsaftermarket.com/technical-resources/tech-videos/how-do-brake-pad-shims-work/
Shim Materials
Brake pad shims are made from various materials, with the most common being:
Stainless Steel – Stainless steel shims are very durable and resistant to corrosion. They are designed to absorb vibration and noise. Stainless steel provides excellent heat resistance as well.
Aluminum – Aluminum shims are lightweight yet sturdy. Aluminum conducts heat well to help prevent overheating. However, aluminum is more prone to corrosion than stainless steel.
Rubber/Ceramic – Rubber or ceramic shims focus more on reducing brake noise than heat dissipation. The soft rubber absorbs vibration to create a quieter brake pad. Ceramic shims can withstand high temperatures.
The shim material affects characteristics like durability, noise reduction, heat transfer, and corrosion resistance. Stainless steel offers the best all-around performance for most vehicles. Aluminum and rubber/ceramic shims have trade-offs but can be ideal for certain applications.
Shim Manufacturers
There are several major manufacturers that produce brake pad shims for both original equipment (OEM) and aftermarket applications:
OEM Manufacturers:
- Bosch – A German multinational engineering company that produces OEM shims for brands like Mercedes-Benz, BMW, Volkswagen, and more.
- Akebono – A Japanese manufacturer that makes OEM shims for Honda, Nissan, Toyota, and other Asian brands.
- Brembo – An Italian company that manufactures OEM shims for brands like Ferrari, Alfa Romeo, Maserati, and others.
Aftermarket Manufacturers:
- Wagner – One of the largest aftermarket brake parts manufacturers in North America.
- Raybestos – A major aftermarket brand owned by Brake Parts Inc, makes shims for a wide range of vehicles.
- Centric – An aftermarket brand by APC Automotive that produces shims and other brake components.
Aftermarket shim manufacturers produce parts for older and newer vehicle models. They offer direct replacements for worn out OEM shims.
The Future of Brake Pad Shims
Brake pad shim technology is expected to continue advancing in the coming years. Some key developments to watch for include:
New shim materials like carbon fiber and reinforced plastics may enable lighter weight designs. These materials can provide the stiffness needed while reducing overall component mass. Lighter shims will be particularly useful in electric and hybrid vehicles where reducing weight is a priority.
Integrated sensor technologies are being explored to provide brake wear monitoring capabilities directly within the shim itself. Sensors within the shim could transmit data on brake pad condition, alerting when maintenance is needed. This could improve safety and reduce maintenance costs.
New shim shapes and multidimensional designs are emerging. Wavy, curved, or convoluted shims may improve noise damping and thermal dissipation properties compared to flat shims. Optimized shim geometries can target specific vibration modes for improved noise reduction.
Overall, brake pad shim innovation will be driven by the wider trends toward lightweighting, sensor integration, and noise/vibration damping in vehicles. As braking systems evolve, shims will adapt to serve their key functions in new and improved ways.