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What Size Brake Shoes Do I Need

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What Are Brake Shoes

How to measure brake shoes and drums

While brake pads and brake shoes perform similar functions, they are not the same thing.

Brake pads are part of a disc brake system. In such systems, brake pads are squeezed together by a caliper against a rotor disc hence the name “disc brake.” The pads squeezing against the rotor generate the friction needed to stop the car.

Brake shoes are part of a drum brake system. Brake shoes are crescent-shaped components with a rough friction material on one side. They sit inside of a brake drum. When the brake pedal is pressed, the brake shoes are forced outward, pushing against the inside of the brake drum and slowing down the wheel.

Drum brakes and brake shoes are parts of an older type of braking system and have become less common on modern vehicles. However, some vehicle models will have drum brakes on the rear wheels since drum brakes are more affordable to manufacture.

Rear drum brake shoes are visible once the drum is removed for service.

How Brake Shoes Work In Drum Brakes

A drum brake system consists of a pan-shaped brake drum, a backing plate, brake studs, a hydraulic wheel cylinder and curved brake shoes. The friction material on the brake shoes faces outwards towards the inside of the brake drum.

Heres what happens when you step on the brake pedal:

  • Force is converted into hydraulic pressure in the brake line from the master cylinder.
  • The hydraulic pressure through the brake line is transmitted by brake fluid, activating a piston in the wheel cylinder.
  • The piston pushes the brake shoes to contact the inside of the brake drum.
  • The brake shoes create friction with the brake drum, slowing the wheel.
  • When the brake pedal is released, stiff return springs retract the shoes to the original position.
  • A screw adjuster in the drum brake assembly extends gradually to compensate for worn brake shoes over time.

What about disc brakes?

The drum brake is a reliable braking system, though disc brakes have superseded it. Youll still find a drum brake on the rear wheel of many cars because theyre cheaper to manufacture than disc brakes.

What about the parking brake?

The parking brake, or emergency brake, is operated from a lever via an emergency brake cable. When you pull the parking brake lever, it forces the brake shoes apart, the same way that hydraulics do.

Now that you know how they work, what can impact brake shoe performance?

Driving With The Parking Brake On

Driving with the parking brake applied can overheat and glaze the surface of a rear brake shoe, as the brake shoes are in contact with the brake drum. High temperatures generated by braking when hauling a heavy load or towing can glaze the rear brake shoes too and this excess heat may increase brake fade.

Now that you know which factors can impact the brake shoe, how can you tell when theres actually a problem?

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Basics Of Drum Brakes

Brake shoe set KNOTT 250x40

Drum brakes are most often used on the rear axle of todays vehicles. They are also very common on trailers. Manufacturers dont use brake pads as the friction material in drum brakes. Instead, a drum brake system has a wheel cylinder with pistons that push brake shoes out against the inside of a spinning drum. This contact slows and stops the rotation of the brake drum and the wheel, bringing your vehicle to a stop.

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Symptoms Of Worn Brake Shoes

The thing about brake shoes is that theyre inside the drum.

Unlike a disc brake pad, theyre not very visible parts, which can make it difficult to identify issues.

However, if theres a problem with your brake shoes, there are still some obvious signs:

  • You hear squealing or rubbing noises when you brake.
  • Your car veers to one side during braking.
  • Theres a noticeable reduction in braking power.
  • Your parking brake isnt as effectiveas usual.
  • The brake pedal sinks to the floor.
  • Your car shakes upon braking.
  • The brake warning light is on.
  • The drum brakes lock up.

If any of these signs pop up, its time for a visit to the mechanic, or better, get one to come to you so that you dont have to drive with a faulty brake system.

Basics Of Disc Brakes

Disc brakes are found on most vehicles today. They are mounted on the front and/or rear axle. To stop a wheel , a disc brake uses a caliper fitted with brake pads to grab a spinning disc or rotor.

What is a caliper?

The caliper is an assembly mounted to the vehicle with a bracket. It frames the rotor, looking and functions like a c-clamp. It contains the following components:

  • Brake pads are a friction material bonded to a metal plate that helps stop your vehicle.

  • One or multiple pistons to push the brake pads against the rotor when you brake.

  • A bleeder screw to allow for servicing the brakes and replacing the fluid.

  • A rubber piston seal that prevents brake fluid leakage and retracts the piston when the brakes are released.

  • A dust boot to keep contaminants out of the cylinder.

  • Anti-rattle clips that add stability.

What is a rotor?

The rotor is made of cast iron or a steel/cast iron composite. Its attached to the wheel hub and turns with the wheel. This is the surface that the brake pads make contact with to slow your vehicle. Heres how it works: when you step on the brakes, pressurized brake fluid pushes against the pistons inside the caliper, forcing the brake pads against the rotor. As the brake pads press against both sides of the disc, the friction stops the wheels rotation.

Rotors can either be solid or vented. Vented rotors have more surface area and can more easily dissipate heat.

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Direction Of Braking Force

The main difference between brake shoes and brake pads is their direction of force. Brake shoes stop the car by pushing outward, while brake pads stop it by moving closer together. Instead of sitting inside a brake drum, brake pads are positioned around a disc called a rotor. A caliper squeezes the brake pads together so they press against the rotor disc, which slows down the wheels and stops the car.

Brake Shoes Vs Brake Pads

Mr. Fixit Explains How to Measure Brake Shoe Size

When it comes to braking systems, most of today’s vehicles have disc brakes with brake pads. As mentioned previously, some vehicles have disc brakes in the front and drum brakes in the rear to help reduce manufacturing costs. On these vehicles, the disc brakes are almost always kept on the front wheels since they can generally handle more stopping force when the brakes are applied. Here are a few more differences you’ll find on brake shoe and brake pad systems.

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Brake Shoe Adjustment Measurement

Step 1

Use a Vernier caliper tool to measure the inside diameter of the brake drum being placed onto the rear brake shoes. The caliper tool employs two sides: one for the interior diameter measurement, the other for the exterior diameter measurement. Use the internal measuring side to measure the inside diameter of the drum, then record the measurement.

Step 2

Manually adjust the opposite exterior diameter side of the caliper and reduce the measurement by 0.024 inches.

Place the exterior ends onto the brake shoe width and manipulate the self-adjuster mechanism on the brakes until the shoes hit each side of the caliper evenly. Be sure to place the caliper ends on the parts of the curved shoes that protrude outward the most. This will allow easy drum installation on the shoes.


What Are Brake Shoes & How Are They Different From Pads

Unlike your running sneakers, your car’s brake shoes aren’t meant to help improve your mile time. They’re actually designed to help you stop your car! In fact, brake shoes are an essential element of certain braking systems, and, contrary to popular belief, they are not the same thing as brake pads. Learn what brake shoes are, why they’re important, and how they stand apart from brake pads.

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Amount Of Stopping Power

Another difference between brake shoes and brake pads is the amount of force each one requires to stop the vehicle. Even though brake shoes typically have larger areas of rough-surfaced material to help create the friction needed to stop the car, they typically don’t have as much stopping power as brake pads on a disc brake system. All things equal, disc brakes generally provide more stopping power much quicker than drum brakes, allowing the car to stop sooner and at shorter distances.

How To Measure To Determine The Size Trailer Brakes Needed For Hydraulic Drum Replacement

BPW brake shoes 200x500 with a full set of springs


Where does the measurement come from to determine if I have 2-1/4 or 2-1/2inch brakes? I need to replace the brakes on a Road King boat trailer with 3700# axles. It seems the wheel cylinder is blown out and rather than buying piece parts you kits seem to be the best option.

asked by: Chris

Helpful Expert Reply:

To determine the size of the brake assemblies you need you have to measure the depth and width of the hub drum on the axle like what you see in the picture I attached. The most common size is 2-1/4 inch wide like the that you referenced.

  • 10 x 2-1/4 Inch Drum
  • 3750 lbs Axle

12 x 2.5 drum trisaler brakes i just want the whole brake whitout botor i need probably 596607

Sounds like you’re looking for the Brake Kit# 23-428-429which is rated for a 7,200 lb axle. This kit comes with both the right and left brake assemblies and it doesn’t come with the hub and drum – just the brakes. 71289

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Measuring Shoe Lining Thickness

Step 1

Clean all the rivets on riveted brake shoes prior to measurement. Much of the friction material that wears away can become trapped and pressed inside the rivets. Use a small straightedge screwdriver to cleans the rivets out thoroughly.

Step 2

Use a tire tread depth gauge. Insert it into each rivet. There can be more than eight rivets on a brake shoe. Measure each by placing the flat base of the tire tread depth gauge onto the brake lining and then pushing down on the sliding ruler. Compare the measurements of each rivet in 1/32 inches to determine even or uneven brake shoe wear.

For bonded shoe measurements, use a brake lining gauge. Bonded shoes do not employ rivets they are glued to the shoe plates. This style of shoe has to be measured from the edges of the brake shoe lining. Take several measurements along the edge of the shoe to compare even or uneven wear. Since there are a few different brake lining gauges, each may employ slightly different procedures. Some use a scissor motion to pinch the actual lining in the end of the tool and compare the measurement on the opposite, wider end. Other gauges simply have a preset thickness and offer different sizes on the same tool.

Regular Wear And Tear

Regular driving will gradually thin the brake shoe friction material.

Eventually, the friction material will start to wear unevenly until the metal shoe backing, or the rivets that hold the friction material, contacts the brake drum.

This results in a horrible scraping noise every time you press the brakes. Your brake pedal will also likely travel farther down to the floor, and the brake system wont respond as usual.

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Brake Shoes What You Need To Know Before Ordering Online

I have seen the question asked many times: “How do I know if those shoes I want to buy will fit my bike”?Many people, myself included, can’t remember or can’t find reliable web information as to the exact measurmentsof the brake shoes that are hiding behind their brake plate.The only way you are going to know for sure is to remove the wheel and find out, in milimeters, the diameterof the brake drum,and the width of the shoes.You could rely on measument specifications that you may have found on your bike, but the wheels from different bikes are interchangable. You don’t know if you are in possesion of the factory wheels, or if the PO has upgraded from somthing else.My 78 Hobbit has the front wheel from a 1970 Honda CT90 on it because the shoes and drum is 50% bigger.

Because it is on hand, I will use this wheel and brake plate from a 77 Peugeot. Of course you will first remove the wheel from the bike and then unscrew and remove the axle nut and washer. This will allow you to slide the brakeplate/shoe assembly off of the axle, exposing the brake drum.

Now , also measure the depth of the shoes. These shoes have a depth reading of 18.12 or 18mm in general.Now when I go online I can shop for brake shoes with the measurments of 80mm X 18mm.


How Do You Measure For Drum Brakes

How To Identify What Type Of Brake Pads You Need

How to Measure Drum Brakes

  • Remove the drum from the wheel employing a drum puller if necessary.
  • Inspect the outer facing of the rotor and locate the stamped maximum diameter or machine-to diameter in the cast.
  • Place the drum face down onto a flat surface so the interior diameter of the drum is facing upward.
  • . Correspondingly, how do you measure drum brakes out of round?

    Always measure the inside of the brake drum before deciding to discard or machine on a lathe. Use a drum micrometer or an equivalent tool to retrieve these measurements. Compare them to the diameter stamped on the outside of the drum. If the drum is scored or grooved, place the tool into the deepest part of the groove.


    Subsequently, one may also ask, how do I know what size brake shoes I need?

    Measure each by placing the flat base of the tire tread depth gauge onto the brake lining and then pushing down on the sliding ruler. Compare the measurements of each rivet in 1/32 inches to determine even or uneven brake shoe wear. For bonded shoe measurements, use a brake lining gauge.

    How do you know when drum brakes need replacing?

    Technical Bulletins

  • Scraping noise while braking.
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    How To Measure Brake Shoes

    As brake shoes wear down from use, the hydraulic wheel cylinder has to push its pistons out farther in order for the shoes to contact the inner diameter of the drum. When the brake lining of the shoe wears away, metal-to-metal contact will occur and can damage the brake drum. There are a couple of shoe styles–one riveted, the other bonded–and they require slighly different ways of measuring. You can also measure the width of an installed shoe to compare it to interior drum diameter in the installation of drum brakes.

    Two Types Of Disc Brakes: Floating & Fixed

    There are two types of disc brakes. They are floating and fixed, named for the type of brake caliper used.

    A floating caliper is the most common type. It has one or two pistons. When the brakes are applied, the inner brake pad is forced against the disc while, at the same time, the caliper body moves closer to the rotor. This action forces the outer brake pad against the rotor.

    The fixed caliper design has one or more pistons mounted on each side of the rotor. The caliper itself doesnt budge or move. Its rigidly fastened to a brake caliper bracket or spindle. When the brakes are applied, only the caliper pistons move, pressing the brake pads against the disc.

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    S For Measuring Brake Drums Properly

    To get a precise measurement of the brake drum, you will need a screwdriver, drum puller, and a micrometer.

    After you have set everything, you just have to follow our simple tutorial to measure brake drums correctly.

  • Remove the bolts or retaining clips from drums that hold everything together.
  • Use a drum puller to pull off the drum from the wheel.
  • Now, search for the maximum diameter in the cast. Most of the time, the diameter is on the rotor on the external surface.
  • Note: You might not be able to find out the interior diameter due to rust. In such situations, you can rely on the specifications chart. For that, you will need the model and manufacturing year of the car, and you will get the measurements.

  • Put the drum on an even flat surface with its face down so that its inner side faces upwards.
  • Now, properly examine the drums interior diameter and hub surface to spot any cracks. If there are any cracks, place the extendable arms of the micrometer in them.
  • After positioning the micrometer, unscrew the lock screw of the arm in line with the micrometer shaft.
  • If the drum is 10.5 inches, keep one side of the micrometer at 10 inches. The other arm should also be at 10 inches but with the addition of four 0.125 inch marks displayed on the shaft.
  • For measurement, put the micrometer anvils in the drum and oscillate them back and forth across the drums internal diameter.
  • Keep an eye on the drums indicator to spot any anomalies such as runout.
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