I’ve been a mechanic for over two decades now, and brake repairs are the number one repair in most workshops.
Brake calipers are a critical part of the brake system. Complete failure is rare, but a binding caliper is a standard complaint, and so too, is a frozen caliper. The best solution for a faulty caliper is to swap it out.
Brake calipers on the same axle (meaning both front or both rear) should be replaced in pairs; this prevents a brake system imbalance. And so whatever brake work we do on one wheel of the vehicle, we should also do on the opposite wheel. Make sense?
Brake Calipers Types
Brake calipers, as you know, are the business end of getting a car stopped. They are responsible for clamping and forcing the brake pads against the rotor. Calipers come in two flavors, Fixed, and Floating.
They both do the same job but go about it a little differently. The replacement process is a little different, too, so it makes sense to identify which type you have.
Fixed calipers are, as their name suggests, fixed. They are fastened to the Knuckle and do not move. A fixed caliper importantly employs at least two pistons, one for each brake pad on either side of the brake rotor.
The opposing pistons of the fixed caliper offer superior brake performance, so you won’t be surprised to know they are typically fitted to commercial vehicles and high-performance cars.
Fixed calipers, then, are not the norm. While they are slightly different from floating calipers, the replacement process is nearly identical.
If your caliper has a piston on both sides of the rotor, it’s a fixed caliper.
A floating caliper is, as its name suggests, it’s a caliper that floats across the rotor. Floating is a strange word to use in the same sentence as brakes, but they are quite safe.
Allowing the caliper to float or move slightly across the rotor allows the caliper to employ a piston (or sometimes two) on one side of the caliper only. The great advantage is cost.
Because the caliper is permitted to move (talking mm here) across the rotor, one piston can apply both brake pads with ease, and only minimal reduction in brake performance when compared to its cousin, the fixed caliper.
Anyhow, since floating calipers are the type most commonly found on passenger cars, it’s the type we cover here in this replacement guide.
How to Remove Brake Caliper
When fitting a brake caliper, we’ll need to open and remove the flexi brake hose. Whenever we open the hydraulic system, we expose it to air, so we will need to bleed the system. Bleeding is the term given to purging air from the hydraulic system.
Bleeding brakes is not difficult, and I have included a link below that covers the process step by step, but you need to be prepared ahead of time. Opening the brake line renders your car unsafe to drive until you perform the bleed process, and bleeding requires fresh brake fluid and a bleed kit.
Tools to Replace Brake Caliper
Removing a brake caliper requires only basic tools and most serious DIYers will have them to hand. Note that many vehicles commonly use Torx head fasteners and so it’s possible you may need a Torx set to remove brake caliper fasteners.
Tools needed include:
- Lugnut wrench
- Axle stand
- 3/8 or 1/2 drive Torx set
- 3/8 or 1/2 drive socket set
- 3/8 or 1/2 drive ratchet
- Wrench set
- Long-handles flat screwdriver
- Catch container for waste fluid
- Wire brush
- Brake bleed kit
- Torque wrench
Supplies needed to fit the new caliper include:
- Brake cleaner
- New foil-sealed brake fluid
- Blue thread lock
As we’ll be opening and removing the brake line at the caliper (Flexi hose), our brake line will begin to empty fluid from the system. It is important to refit the leaking hose immediately to the new caliper so as to prevent it from emptying the reservoir system completely.
As the hose is fixed at the chassis, it does not rotate, instead, we’ll need to rotate the roto off the hose and the new caliper back onto the hose. This is a little fiddly but not very challenging once you are prepared.
But we are under time pressure, allowing the system to empty will cause bleeding issues later, and ABS systems may require a scan tool to activate the pump in order to purge the now airlocked ABS modulator – You can avoid this by being fully prepared before opening the flexi hose.
- Fill brake fluid reservoir to top
- Have your new caliper ready; calipers are marked L or R; make sure you have the correct one. (bleed valve always faces upwards)
- Have a wrench to open the flexi hose to hand
- Wear disposable gloves and have some cleaning cloths to hand
Now you are prepared.
Caliper Removal & Fitting Process
- If your caliper employs a spring clip, go ahead and remove it.
- Remove caliper fastener dust caps
- Remove both caliper fasteners
- Use wire brush to clean the flexi hose threads at the caliper
- Loosen the flexi hose fastener at the caliper by a quarter turn (counter-clockwise)
- Use a long-handled flat screwdriver to pry the caliper off the rotor
- While holding the flexi hose turn the caliper counter-clockwise off the flexi hose and set the old caliper aside
- Wipe the threads of the flexi hose clean with a cloth
- Offer new caliper to the flexi hose and thread clockwise until seats
- Place the caliper on the rotor and tighten the flexi hose fastener
- Clean up splashed fluid with brake cleaner
- Clean and lube (silicone grease) the caliper fasteners (slides)
- Fit caliper fasteners and tighten (typically 26lb-ft (35Nm))
- Fit caliper fastener dust caps
- Fit the caliper spring clip
- Top up brake fluid reservoir
- Repeat the process on the opposite wheel
As the calipers are new, the brake system will require bleeding.
How to Bleed Hydraulic Brakes
Bleeding the brakes isn’t difficult but requires a special tool and a technique to nail it successfully. The tool required is known as a bleed kit, and you can either buy one or make your own.
I’ve covered the process of bleeding your brakes step by step using a homemade brake bleed kit and you can check that out here – How to bleed brakes
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.