Brake discs

/// Mister-Auto’s DIY Guides

www.mister-auto.co.uk - 0844 338 00 21*Please note: free and informative document for which Mister-Auto does not accept any responsibility or liability.

MOUNTING BRAKE DISCS

Brake discs are made of a heat resistant cast iron alloy. Due to the heat generated by the friction between the disc and the brake pads, it is important that the former do not get damaged. Despite their resistance against elevated temperatures, brake discs do wear over time resulting in them needing to be replaced about every 32.000 miles. To get the most of your braking force, it is advisable to replace your brake pads at the same time as your discs.

BRAKE DISCS

On the Mister-Auto website, you’ll find a wide selection of suitable brake discs for your car. For the most well-known car makes you’ll be able to choose from among brands such as Mintex, Ferodo, Bosch or TRW. Be sure to choose brake discs from a quality brand as these are essential car parts for your safety. Thanks to Mister-Auto’s discount prices, you’ll be able to save considerably on your brake parts, so please don’t be too tight on your budget. A pair of quality brake discs will cost you between £50 and £100.Prior to ordering a brake disc reference, you will need to check some characteristics and technical details directly on your vehicle. Mister-Auto offers you a large selection of brake discs from different brands but you’ll realise that some correspond to your original discs while others don’t. To avoid ordering the wrong discs, it is important to check the following:• the disc diameter: measure it

with a slide calliper to find out which diameter you need. This is very important because one

vehicle can be equipped with two or even three different sizes of brake discs.

• The type of brake disc: do you need vented or solid discs? A vented brake disc will have small holes on the surface or a small space between the two brake disc rotors. As a result, solid and vented brake discs are not equally thick. In general, you’ll find vented discs at the front of a vehicle and solid ones at the rear. It is important to check which kind you need because they cannot be mounted interchangeably.

• If the rotor edge is not too rusty, see if you can find a reference. You might have to use a file or a piece of glass paper to scratch off a bit of rust and dirt.

I f y o u a r e u n c e r t a i n , w e recommend you ask your local mechanic or check a technical magazine. Mister-Auto has also made technical details as well as assembly schemes available so that you can easily compare those with what you find on your vehicle.

HOW TO CHOOSE BRAKE DISCS?

TIPS FROMMISTER-AUTO

• Replacing brake discs is a fairly easy task and therefore

upkeep you can carry out yourself.

• Always start by parking your car on a flat surface.

When lifting your car with a jack, make sure it is stable and secure before you start dismounting parts. Underneath the vehicle you will find indicators for safely and securely lifting it.

• Equip yourself with the right tools. The calliper guide pins are tightly secured so you need special equipment such as a pin removal tool to avoid damaging the nuts when taking them out.

30 mins

DIFFICULTY

TIMEEQUIPMENT- A set of tx-star keys- A set of breaker bars- A set of flat pliers- A pair of gloves- Protection glasses- Two 2 tonne axle stands- Combination pliers- 1 pot of silicone grease

http://car-parts.mister-auto.co.uk/en/front-brake-discs_lg900007/



BRAKE DISCS

WHAT DO I LOOK AT WHEN CHECKING MY BRAKE DISCS FOR SIGNS OF WEAR?

In most cases brake discs are replaced when they have lost 10 to 15% of their original thickness. This equals about 1.5mm at most. At that point your brake disc is “scorn” and absolutely needs replacing. A brake disc width can easily be measured with a slide calliper.

There are three cases in which you will have to replace the brake disc :• Corrosion or wear: due to use,

your disc has lost 10 to 15% of its original thickness. Especially at the rear, the brake discs may corrode as the braking force is not as intense as at the front. Light corrosion is not a problem but if the disc has corroded to the point that the brake pads do not clean the rust off anymore, this can lead to pitting.

• Scra tch ing and scor ing : a scratched or scorn brake disc seriously compromises your safety due to a lack of braking force. Brake discs can become scorn or scratched if the pads have no friction material left on them and the metal backing is pressed directly against the disc. It is therefore important that you regularly check the state of your brake pads and callipers. A stuck calliper piston can also result in scratching as the brake pads are not released from the disc when you take your foot off the pedal.

• Distortion: if you notice the brake pedal trembles when you are pressing it, there is a big chance your discs are warped. Brake disc distortion is usually caused by uneven heating and cooling. The shape of your brake discs is altered resulting in them trembling

and juddering when you press the pedal. Worn and thinner brake discs warp more easily than new ones.

In some cases you might not need to completely change your brake discs. However, it is extremely important to always check if your brake discs can be reused or not. • when replacing your brake pads

rather late and the metal backing of the pads has run on the discs, critically look at the brake discs. Worn brake pads with little or no padding running on your brake discs can lead to scratching. Take a good look at your discs to determine whether they are so damaged that you need to replace them or whether there is only minimal scratching in which case you might be able to reuse them.

• if you see your brake disc has a bluish tinge. If your disc has become overheated, the cast iron will be tinted with a bluish glow. Despite being extremely heat-resistant, frequent heavy or prolonged braking such as when holding the car back on a long downhill run or driving with a heavy trailer or caravan can result in over-heating. To avoid this, prefer engine braking over using your brakes. Use a lower gear if it is necessary to reinforce the engine braking power. Also avoid just applying the brakes if you feel you are losing control of the vehicle or need to support the engine with the brakes. Instead, press down the pedal in a pumping movement, thus varying the braking force and avoiding over-heating.

TIPS FROMMISTER-AUTO

• A r r a n g e y o u r too ls and par ts . E s p e c i a l l y t h e

smaller parts can easily get lost, so put

a l l your bo l ts ups ide down on their heads side

by side. Prior to mounting your new brake discs, you’ll need to disassemble the old ones: prepare and clean your working space. Take care to dismount and arrange all the parts one by one paying close attention to the order in which you are dismounting them. If you start with the front brakes, completely replace everything before starting at the rear. That way you won’t get mixed up with the different parts and if you are uncertain about something, you can easily check on another wheel.

• Push the calliper piston back ensuring you don’t damage the rubber protection boot with the tool you are using. It is in fact easiest to use the piston-side brake pad as a pressing surface. Wedge a screwdriver between the disc and the pad and use it as a lever.

• Remember properly tighten the nuts and bolts and ensure you used all the parts you dismounted. Finish by pressing the brake pedal a couple of times to apply the brake pads to the disc. This is very important. If neglected, you’ll experience a severely reduced braking force when you are applying your brakes for the first time after mounting new discs.

http://car-parts.mister-auto.co.uk/en/front-brake-pads_lg900005/



REPLACING BRAKE DISCS IN 14 EASY STEPS

Park your car on a flat and well-lit surface. Start by loosening your wheel bolts. Take your rolling jack to lift the car. Ensure it is stable and cannot crash to the floor. Then completely dismount the wheel. If you have wheel trims, pull to take them off.

Unscrew the guide pins. The brake disc is now only kept in place by a small but long screw. Take the tx-star key or a star screwdriver to unscrew.

Push the calliper piston back into the brake calliper. Drive a screwdriver between the inner brake pad and the disc and use as a lever. If the brake pads are worn, they will be stuck against the disc.

Unscrew the calliper. Use combination spanners or a ratchet to loosen the inner guide pin and unplug the brake pad wear contact if you have one.

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Push back the piston

Unscrew the guide pins

Release the caliper Release the caliper

Release the caliper

BRAKE DISCS



Take the disc off the wheel hub. Drive a wedge behind the hub and take a rubber ring. Carefully tap onto the wedge to loosen the brake disc which will be a bit stuck onto the hub due to corrosion.

Degrease the new brake disc with brake cleaner.

Clean the wheel hub with a wire brush to really take off all the rust and brake pad dust. It is essential to thoroughly clean the hub as dirt or corrosion can easily lead to the premature warping of your new brake discs.

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Lift the caliper

Lift the calliper and take out the brake pads by hand. Secure the calliper without letting it dangle by the brake hose.5

Release the brake disc

Clean the hub using a wire brush

Ensure your hub shines like new

BRAKE DISCS

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http://car-parts.mister-auto.co.uk/en/caliper_lg78/



Connect the brake pad wear contact if you have one.

Press your brake pedal a couple of times to apply the brake pads well against the brake disc rotor. You’ve finished when the pedal starts feeling heavy.

Put the wheel back on.

Check the brake fluid levels and top up if necessary. Make sure you don’t add too much. Adapt your driving style to avoid premature wear on your new brake parts or a reduced braking force during the first 150 miles after fitting new brakes.

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Push new brake pads into the calliper. Use some screw sealant on the bolts (generally the sealant will be included with your brake pad set). Put the calliper back in place and fasten the guide pin. All the parts ought to fit together like a jigsaw.10

FinishFinish

Mount the new brake discs and attach them with the guide pins. Don’t tighten those too strongly to avoid them breaking off inside.

9Mount the new disc

Degrease the new disc

BRAKE DISCS

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Automotive

Brake discs