What are Brake Discs? How do they work? How do I know when mine need replacing? When it comes to your motor vehicle’s braking system, a lot of questions may arise. We’re here to try and answer some of them for you, focusing mainly on your brake discs.

Brake discs have a simple function, they’re simply designed to slow your vehicle down. In case of an emergency they also need to be able to stop your vehicle from moving as effectively as possible.

Although the role that brake discs play is simple and straightforward, they’re one of the most important components fitted to your car. In some cases they can be the difference between life and death. Because of this, there’s a great deal of engineering that’s gone into manufacturing various types of brake discs. There’s a lot of variables that need to be considered when manufacturing discs that work well, things such as; BHP (brake horsepower), vehicle weight, durability of the materials and effective cooling capabilities. All of these will have a great impact on the final design of your brakes.

Brake discs work by being securely fastened to each wheel’s hub flange, this hub flange is then connected to either an axle or a drive shaft. As you press your foot down on the brake pedal, fluid is forced through your brake lines and fills up your brake calipers on each wheel. As the caliper fills with fluid, it pushes a piston out, which inturn causes a squeezing effect to take place. As the piston extends outwards, your brake pads are pushed up against your brake disc, causing your wheel to slow down. The harder you press on the brake pedal, the harder your caliper squeezes and the quicker you slow down or stop.

It’s a simple system in theory, but a vital one. This is why choosing the correct discs for your vehicle is incredibly important.

Types of Brake Discs

It’s not always easy to select the correct parts for your vehicle when there is so much choice to choose from. We’ve put together a small section to help you better understand the different types of brake discs, helping you to make your decision.

Solid Brake Discs -

These are probably the most basic brake discs available. They’re essentially a solid, flat smooth disc that is typically made from iron. They are cheap to manufacture and to purchase as a consumer because of their simple design. You can usually find this type of disc fitted to smaller, lighter vehicles with a low BHP.

This is because they are very inefficient when it comes to heat transfer. The solid material causes the disc to heat up quickly which can lead to hot spots, fractures and a warping effect. This is why they tend to only be fitted to smaller vehicles that don't require such a heavy braking capacity.

Vented Brake Discs -

Vented discs are similar to the solid brake disc design, only instead of having one solid surface, they have two, with a groove in between the two surfaces.

This groove or “vent” in between the two braking surfaces allows for a better heat transfer. As the wheel is turning, air is permitted to flow in between the braking surfaces and creates a cooling effect, which prevents hot spots, fracturing and warping from taking place.

Vented discs tend to be fitted to a more “standard” size vehicle. This vent allows the extra heat created - because of the added weight and power of the vehicle - to be transferred. Which keeps your discs working as they should.

Drilled, Slotted or Grooved Brake Discs -

In the same way that adding a vent allows for better heat transfer, drilled holes, machined slots and grooves provide the same benefit.

Instead of having just a vent in between the two braking surfaces, these types of discs allow extra air flow around the disc in order to cool it more effectively. These types of discs are usually fitted to heavier and higher performance vehicles to help compensate for the extra heat that is generated through braking.

Along with cooling, these machined slots and grooves have been designed to prevent brake dust build up. The dust that’s created from your brake pads as they’re operating can cause an additional temperature increase, so it’s important to get rid of the dust build up as efficiently as possible.

Disc Thickness

Another variation that is offered depending on your vehicle is the thickness of the brake disc surface. Whilst the overall design of the disc may appear to be similar, it’s important to check what thickness the braking surface of the brake disc should be.

The thickness will be dependent on the overall vehicle weight, BHP (brake horsepower) and braking force. A thicker brake disc will decrease the amount of heat that is created when under load, but it can also affect the ride quality, as a thicker disc equals more weight on the suspension.

The Warning Signs

You may not always realise when your brake discs need replacing. So, here’s some things to watch out for -

  • Brake “judder” - If you can feel a pulsing through your brake pedal, this could indicate a warped brake disc.
  • Grinding Noise when braking - If you haven’t used the brakes for a long period of time, or live by the sea, then this noise can likely be an indication that your brake discs have become corroded. The corrosion will cause a decrease in braking performance so it’s always best to get them checked if you’re unsure.
  • High pitch squealing when braking - This is more common when poor quality brake discs have been fitted or if you have fitted brake pads that aren’t compatible with your brake discs. The noise tends to only get worse until the correct parts are fitted.
  • Thin/ discoloured brake discs - If you’ve noticed that your brake discs are wearing quite thin or are turning a slightly bluey colour, this could be a sign that your brake caliper is starting to seize. You only have a set limit on how thin your discs can get, so if you’re unsure, get them inspected by a professional.

Maintaining your Brake Discs

Brake maintenance as a whole is vital in order to keep your brakes working effectively. Here are some of the best ways to keep them in tip top shape;

— Use them. Brakes will corrode, seize and can even warp if they aren’t in use for long periods of time, so make sure they’re being used on a regular basis.

— Servicing, by having a brake service, you can prolong the life of your discs. This will allow the calliper, pins and brake pads to move freely which prevents excessive heat build up that could ruin your brake discs.

— Check your brake pads regularly. If your brake pad material runs out, you will be braking on the outer metal of the brake pads, this will not only heavily affect your braking efficiency but will also ruin your brake discs. If you can replace your pads before they reach this stage (highly recommended) then you have a better chance at prolonging the life of your brake discs.

Installation Precautions

So, you’ve read through all of the material provided. You now know when your discs need changing, which discs to choose and how to maintain them. Now you’re deciding whether or not YOU can change them yourself.

As stated earlier, the brakes on your vehicle are vital, so if you’re unsure about how to work on them, consult a professional.

Here we will list a few of our top tips when it comes to installing your new discs.

  • Always clean the brake pad cradle, the hub flange and the slider pins. This will keep your brakes working properly and prolong the life of your pads and discs.
  • Use copper grease to help lubricate components that are designed to rub against each other. Do not lubricate brake pad material or the face of brake discs.
  • Change brake discs in pairs, across the axle (e.g both the fronts or both the rears). This will keep your brakes wearing evenly and will give you a more balanced braking ability.

We hope that you have found this post helpful if nothing else. Please feel free to refer back to it when you need to, and if you have any questions or queries regarding brake discs, or maybe you need help selecting the correct ones for your vehicle, then feel free to get in touch

We look forward to hearing from you.