Car brakes are mission-critical components and you’re doing the right thing, inspecting regularly and asking questions.
Most cars use brake calipers and there are two main types, fixed and floating. Fixed calipers are fixed firmly to the brake carrier and the more common floating caliper is free to move laterally on its sliding pins.
In this post, you’ll learn how to check that your brakes are indeed tight. You’ll learn about common brake problems. You’ll also learn a little more about fixed, floating calipers and how they work. And you’ll find a useful brake system checklist.
Loose brakes aren’t a common complaint, of course, it is possible. Most cars are fitted with a floating brake caliper system. It is by nature free to move laterally by about an inch or so and seeing this could understandably alarm those unfamiliar with the system.
Floating caliper movement is normal behavior. You can easily check if the caliper is secure. It is fixed to the brake carrier using two slide pin bolts, the torque setting is usually about 35Nm, and you’ll likely need to remove the pin bolt dust caps to check.
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Fixed calipers, the name gives the story away really. The first caliper was a fixed caliper and was used commercially by William Lancaster in the UK around the 1900s, on his Lancaster motor cars.
Although superior to its predecessor, the drum brake, it took amazingly, another 50 years before they became mainstream. Mostly because of the cost of manufacturing, drum brakes are just cheaper to make.
Development of the caliper was accelerated during the war years, primarily for use on the aircraft landing gear.
By the mid to late ’50s, the caliper was established as the benchmark and the future of automotive brake systems.
Its predecessor, the Drum brake, although inexpensive, was woefully problematic. Brake fade, dragging brakes are two of the more common problems. The brake drum, which is a solid cast steel drum-shaped component, expands as it heats.
This causes the friction surfaces to move further apart which resulted in the brake pedal traveling further to the floor, it’s known as brake fade.
How does fixed caliper work?
It’s a hydraulic system, a small force applied at the brake pedal is multiplied at the business end, the caliper.
The fixed caliper sits fixed over the spinning wheel rotor and it contains two pistons (or more) one either side of the rotor, against which the pads rest.
As the brakes are applied, the force is transferred through the fluid. This pushes the pistons (aka Cups) outward where the pads contact the rotor simultaneously and slow or stop the wheel.
In the automotive world, the fixed caliper is now a rare animal indeed, reserved for high-end cars, performance, and racing cars.
The fixed caliper is more rigid and offers better braking performance. The piston on either side of the caliper means the pads bite at the same time. Racing fixed calipers may use twin pistons on either side of the caliper, this allows for a larger rotor and unbelievable stopping force.
The Floating Caliper
The floating caliper, got its name because… well you know, it floats. But what does that mean? The floating caliper was conceived as an answer to effective caliper brakes but at a reduced cost and weight.
And they are wildly successful. They are the most common type of brake caliper fitted to cars and many light commercial vehicles.
Less is less, usually yes but in the case of the floating caliper, the trade-off is hardly noticed by most, unless your name is Dale Earnhardt.
How does it work?
The floating caliper sits over the rotor the same as a fixed caliper, but the floating caliper is fastened using two pins or bolts that allow the caliper to slide laterally when braking. This is what makes this caliper a floating caliper.
So what’s the point of that? As the caliper has the ability to slide laterally across the rotor, it only needs to employ a single-piston.
On initial application of the brakes, brake fluid forces the single inner piston outward and the inner brake pad meets the inside of the rotor.
Progressive foot-brake pressure will then cause the brake caliper to slide across on its pins (Bolts) and at the same time pushing forcefully the outside pad against the outer rotor surface.
As the brakes are released the caliper moves back to its rest position. The movement here is small, measured in mm, but it’s enough to get the job done.
Not all floating calipers are single-piston some are twin which will be employed on larger heavier vehicles.
So what’s the downside to this cheaper alternative? The brakes aren’t quite as responsive or strong as fixed caliper brakes, but truthfully in everyday driving, you wouldn’t notice. Uneven brake pad wear is a characteristic of the floating caliper brake setup.
There are a few common mechanical issues, but mostly they’re eliminated by regular brake inspection and maintenance. The most common problem associated with the floating caliper is binding.
Moving parts need love, as these calipers slide on pins they are prone to corrosion and binding. This is quite a common problem and comparing inboard and outboard pad wear is an easy way to check for problems.
You won’t even need to take a wheel off, a good inspection light will allow you to compare thicknesses. The inner will always wear more than the outer since it meets the rotor first. If the inner pad is close to half the thickness of the outer, you likely have some sticking slide pins.
Common Brake Problems
Brakes work hard and are under tremendous stress. Problems are common but mostly they aren’t serious. Brake failure today is rare. The most common brake system problems and the fix’s are:
- Squealing – Remove, clean, replace pads, pad retaining clips and using Moly or Graphite dry grease, coat the pad arms and backs.
- Brake grinding noise – Replace pads and check for trapped debris in rotor, check also rotor wear.
- Dragging – Clean and lube (Silicone based only) or replace the floating caliper slide pins.
- Soft brake pedal – Bleed brakes and check for leaking union, replace fluid if older than 3 years old.
- Hard pedal – Check brake booster operation, vacuum hose
- Pads don’t bite – De-glaze the pads or replace
- Pedal vibration – Rotors are warped and need replacing.
- Steering vibration – Rotors are warped and need replacing
- Thud noise when braking – Replace the pad clip retainers.
- Rubbing noise – Rotor corrosion, a drive cycle with several medium to hard brake applications will clean the brakes.
- Brake fading – Flush and replace brake fluid.
- Pedal going to the floor and won’t bleed – Check master cylinder
Why do my brakes rattle? Brakes commonly rattle because the brake pad retaining clips are worn out or missing. This allows the pads to vibrate and is often heard as a rattling sound inside the car. Cleaning the brakes and replacing the clips usually fixes the problem.