Back-to-school maintenance: EV brake job breakdown

EVs have two braking systems: the hydraulic (friction) braking system and the regenerative braking system. We’ll cover how these systems differ from one another and how an automotive technician completes a brake job on EVs. 

Hydraulic brakes 

These brakes, also called friction brakes, use brake fluid in a confined space to apply brakes to the wheels. Whereas air compresses when it gets cold and decompresses when it warms up, liquid does not. This helps keep brakes operating consistently. If air gets into a hydraulic braking system, the system is unfit for use. 

Hydraulic brakes use friction to stop the wheels: 

1. Press the brake pedal in the cabin to activate the hydraulic system. 

1. Brake fluid travels through hoses to the brake caliper. 

1. The brake caliper squeezes the brake pads against the brake discs. 

1. The resulting friction brings your vehicle to a complete stop. 

Think of how fast your car comes to a stop when you slam on the brakes: that shows you how fast this system can operate. EVs and hybrids have one for when immediate stopping is needed. 

Gas-powered vehicles only use hydraulic brakes, whereas EVs and hybrids use hydraulic and regenerative brakes. 

Regenerative brakes 

Hybrids and EVs use regenerative braking to regain some power in their batteries. Whereas brakes on gas-powered vehicles create a lot of heat that is dissipated into the air, regenerative braking converts much of that heat into electricity and transfers it back into the battery. This is why an EV motor is often referred to as a motor-generator: it’s a motor when you’re moving and an electrical generator when you’re braking. 

Here’s how it works: 

1. You release the accelerator or begin pressing on the brake pedal in the cabin. 

1. Your vehicle begins to slow, which produces kinetic energy. 

1. The motor-generator switches gears, so to speak, and changes much of this kinetic energy into electricity that it feeds back into the battery. 

If you need to brake hard, your vehicle’s hydraulic system will kick in. Hydraulic braking is best for stop-and-go city traffic. It’s less useful on the highway. 

What’s involved in a brake job 

When talking about a brake job, the technician will focus on the parts that come into contact with the wheel. If you’re experiencing specific problems with braking, mention them to your auto technician so they can see if a more thorough inspection is needed. 

These are the general steps that automotive technicians follow when completing a brake job on an EV. You’ll notice that the focus is on the hydraulic friction brakes. 

1. Place the car on a hoist. Because EVs are all-wheel-drive (AWD) vehicles, all brakes must be inspected and adjusted at the same time. It’s also easier to service a car on a hoist. 

1. Remove the wheel. The technician will remove the wheel cover, unscrew the lug nuts, and take off the wheel. 

1. Disassemble the brake assembly. This gives the technician easy access to all brake components, which they can then inspect for damage. 

1. Clean all components. The technician will sand, scrub, and wash all the brake components. They will also inspect the brake pad adhesive, which often needs to be replaced at the five-year mark. If a technician finds more damage, they will call you to request permission to repair it. 

1. Replace any damaged components. Always feel free to come to the shop to inspect the damaged components before they are replaced. Look for rough surfaces, rust, dimpling, and excessive wear. 

1. Lubricate surfaces. So that your brakes function smoothly, the technician will apply lubricant where needed. 

1. Reassemble the brake and wheel. The technician puts everything back in its place and tightens and torques where needed. 

Once all brakes have been inspected, your car is ready for you. You should notice a marked difference between how your brakes worked before the brake job and how they work now. 

How often should EV brakes be inspected? 

General wear and tear isn’t the only reason to get brakes inspected. The less frequent use of your hydraulic braking system can leave it open to rust, for example. Plus, no matter how infrequently your car initiates the hydraulic friction system, your car still drives through salt, sand, and ice during a Canadian winter. That’s why having them inspected every one to two years is a good idea. 

Although friction brakes on EVs generally require fewer repairs, having them inspected with your regular inspection is a good idea. Regenerative braking does not involve friction, so any inspections on that system focus on the electrical components of the vehicle, especially the motor-generator. 

So, although you can expect fewer repair costs with your EV braking system, still plan to get it inspected regularly. 

For full details on how an EV brake service will look, check out the video below, which dives into the steps of a brake service on a Tesla vehicle, or contact your local AUTOPRO service centre. 

Photo: iStock-538372327