Taking a brake from it all
This is an article is primarily based on a 2002 VW Bora, but I’ve changed discs and pads on many a car down the years and the basics are virtually the same for standard systems. Because car makes and models do vary we suggest you talk to a good workshop manual to get an overview of the specifics for your car. In case you are not reasonably competent at car mechanics please leave work to a specialist, as always.
If you’ve got a big brake four caliper system, or some high spec carbon ceramic solution, or a solution where the rotor (friction plate portion) and hub of the brake disc are separate components then you may need to acquire more information.
It covers the leading pads and discs specifically however the same principles can be applied towards the rear of the car, with the only provision being that this rear will have some form of handbrake system – this will usually be a cable and lever assembly that presses the pads on the discs or in some cases a compact, separate drum or disc system. In cases like this grab your Haynes manual and look up what to do. In the case of a cable it will simply need disconnecting.
Changing brake discs and pads.
The tools you are likely to need will be a wheel wrench, a socket set, the specific removal socket for your caliper floating pins (explained below), a set of pliers, a piston windback tool, some copper grease and lots of rags. A torque wrench is helpful but not absolutely necessary. The windback tool shouldn’t set you back more than around £20. In the past I have used a big long lever to push the piston back and an adjustable spanner plus a flat-bladed chisel to turn a piston back and trust me, a windback tool can perform both these jobs and make them much, much simpler.
If you have the right tools and know what you are doing, changing brake discs and pads is a relatively straightforward job.
Changing discs and pads is absolutely one of the easiest jobs you can do technically and given the price you can get new parts from over the Internet currently, can save you a good amount of money.
If it’s the initial time allow yourself at the very least an half and hour to two hours.
Exactly what is a brake system anyway?
This can be a fair question and it helps to understand the principles involved. Once you put your foot about the brake pedal the braking system magnifies that force and uses it to make a piston push brake pads against a disc. The friction with this slows you down. The fundamental idea is a simple as that.
The piston is held inside a housing which is installed on metal pins that hook it up to the “caliper carrier”. The saying “caliper” is used to describe the whole piston housing, and so in this post I use “piston” for just the piston and “caliper” for the piston housing.
The metal pins allow the caliper to float forth and back, which ensures that as being the discs and pads degrade the piston follows them, so the whole system is self-adjusting. The caliper carrier is itself bolted to the bottom of the suspension strut near the hub which the brake disc and therefore the wheel are bolted.
Usually you can replace brake pads 2 or 3 times before you need to do the discs also. Before you approach that minimum, the discs will have a minimum thickness which is tested in your MOT and as standard discs are very cheap to purchase it’s often worth replacing them, however. Some cars also have disc pad wear sensors. This can be an electrical cable connected to the inner pad using one side of your car. You’ll need to disconnect this.
If your new pads don’t have them it is not going to affect your braking, but you will definately get a light on your own dashboard that you’ll must either ignore, or receive the warning removed electronically. For instance, on VAG group cars this can be removed using the vagcom utility, as well as other cars have similar systems. Ask in our forum for additional information.
General tips before you start.
It’s been said frequently but it’s worth saying again; never, ever work under the car with just a jack. Saving yourself £10 or £20 for a pair of axle stands is not worth giving yourself an accidental leg amputation.
Secondly, when you’re utilizing the wheel off, loosen the wheel nuts before you jack it up. This way you won’t rock the auto off the jack or stand while you make an effort to remove a nut that’s been place on with an air gun. In a similar manner, when putting the wheel back on, tighten the nuts hand tight after which a small turn with the wheel wrench, then lower the wheel to the floor before fully tightening. Otherwise tighten about half a turn again once the wheel is down if you have a torque wrench then use it.
Lastly, if you’ve not done this before, take some photos as you go, so you can look back to them if you’re not sure what went where.
Ok, let’s get cracking.
Ok, so let’s hop on with it. The first thing is to locate your brake fluid reservoir. This usually has a bright cap, yellow, green or red, along with the cap will have sensor wires coming out of it. If you’re not sure your handbook should be able to tell you where it is. Get rid of the cap and have a look at the level. You will need to monitor this as you may work. Right now as your discs and pads are worn the piston will be fully out, and winding it way back in will increase the level. It could be lowered through a siphon or syringe, to dip to the fluid and draw some up. Whichever way you are doing it be careful not to get brake fluid for you or the rest of the engine bay. Brake fluid is not good stuff. The cloth must be clean to avoid getting dirt into your brake fluid.
So, take the cap off, and wrap some cloths around the reservoir, to help stop any accidental drippages.
Jack the auto up then secure it on an axle stand. Get rid of the wheel and you ought to see something similar to the following:
What you are considering here is the brake disc itself, the caliper to the left, and also the wire that can help keep the caliper tucked into the outer brake pad, that you can see behind the wire. Most systems have some kind of retaining wire. You can also see the top of the caliper carrier which supports the caliper in place. The caliper moves on sliding pins which can be bolted for the carrier.
Here’s another picture from the top:
You can see the brake fluid pipe getting into the caliper, and the topmost sliding pin. There’ll be another underneath. These pins are usually removed with a T-socket or spline socket, so you will need the specific one. Google can usually let you know which one.
Taking off the pads and caliper:
So, if fitted, go ahead and disconnect the pad wear sensor cable.
When you have one, use a pair of pliers, or a screwdriver, and remove the retaining wire, again. This may be fiddly. Make sure you definitely learn how it looks for when you are putting it back on.
Now remove the sliding pins. These are typically in a housing, covered with a plastic cap to stop gunge getting in. Here you can see me removing the top one:
Some pins are screwed directly into the carrier and merely need one socket or T-bit to get rid of. Others, often on the rear brakes, screw into a bolt that itself screws in the carrier. You will need to use a spanner or wrench on the bolt to stop it rotating as you remove the pin, although in such a case the bolt does not have to be removed. When the pins are removed they should be cleaned associated with a deposits, or replaced with new ones if there is any damage to them. This makes sure the caliper slides freely when you reassemble.
Now both pins are removed the caliper needs to be pulled away from the disc and pads. This can sometimes be difficult if the pads are seized onto it. You might find some gentle persuasion with a hammer is necessary to break the seal. If you’re not changing the discs be careful not to damage all of them with the hammer while you do this. You may also get the inner pad that’s on the side that the piston is will have small metal arms that hold the pad on the inside of the piston. In this case when you slide the caliper out of the carrier the pad includes it.
When the caliper comes away support it and don’t permit it to hang on the brake fluid pipe. Make use of a cable tie or bit of string and secure it out of the way high on the suspension spring.
Take the other brake pad away and you’ll then see this, which is the empty caliper carrier:
If you’re only changing the pads you will not need to do anything else. Go straight to the reassembly section.
Removing the caliper carrier:
If you’re doing the pads and the discs then you will need to remove the carrier also. This is the two bolts you can observe at the top of the image. A little tip is to slacken the bottom bolt first but don’t fully remove it until you have removed the very best one. Using this method you’ll stop the carrier swinging up as you turn the top bolt.
Removing the disc:
Once the carrier is removed it is possible to remove the disc. The disc is kept in place mainly through the wheel nuts themselves, as well as a small screw. This screw is a complete pain. It will most likely be seized, and will either snap in half when you remove it, or you will have to make use of a hammer and screwdriver to knock it round, so ruining it anyway. Whatever happens Make sure you don’t need to worry about it. It’s pretty much superfluous, and often replacement discs have neither a new screw nor a hole to adhere it in. Remove it nevertheless, you can and also the old disc will come away. If it doesn’t it may have heat welded itself on the hub. Get a hammer and present it a few smacks to get rid of the seal.
Get a cloth and wipe the face of your hub which had been behind the disc, eliminate any old gunge that’s there. Get some fresh copper grease and put some about the hub. This will help to stop the latest disc adhering to the hub again. Supply the disc around the hub. If you do have a whole new screw use it. If not use a couple of the wheel nuts to hold the disc loosely in place, which you can see is the thing that I have done in the last picture in this article.
When you’re cleansing the caliper and carrier for reassembly pay special attention to the various components that touch the brake pads and where the brake pads sit in the carrier. If the slots are rough or dirty this can stop the pads moving freely and cause premature wear or brake seizure.
Now it’s time and energy to put the caliper carrier back on. Give it a clean with a stiff brush and cloth to remove dust and bits, before you do this. Use a little bit of copper grease in the end of your bolt, again it helps to avoid seizure and make it easier to remove it the next time. If not, don’t worry, obtain it as tight as you can, you’ll not strip these bolts, if you have a torque wrench use it.
Once that’s done you are at the point of putting the new pads on. Provide the caliper a clean with a stiff brush but try not to damage the rubber sleeve that surrounds the piston. If this is damaged it can let dirt in which can seize the piston.
Take the outer pad, the one which is not about the piston side. Use a little copper grease to coat the part of the caliper carrier that the ends of the pad touch, as well as on the back of the pad where little arms of the caliper will touch the pad. Put the pad in place. Coat the parts in the inner side of the carrier where the inner pad will touch also.
You now must wind or push the piston back. Front pistons usually only need pushing. Rears, especially if they are also hooked up towards the handbrake assembly, may need winding back. You can usually tell if a piston is actually a windback one if it features a slotted end. In either case the basic principle is identical. In the picture below you can see me utilizing a tool in such a case to push the piston back. The tool I have also has an adapter that can fit into the slots of any windback piston and turn the piston as it pushes it back.
The most important thing is to check your brake fluid level when you wind the piston in, and remove brake fluid as necessary. You also need to be mindful again as you wind back not to damage the rubber sleeve.
In the event that the piston has seized then although you can often utilize a windback tool to force the piston back I would recommend that you get the caliper changed as soon as you can as it may well seize again in the same place.
Once the piston is fully wound back remove the tool, get the remaining pad and in case it is one of the pads which secure for the piston, input it there. Otherwise place the pad onto the caliper carrier as you did the other pad.
Offer the caliper up to the carrier. You have to reasonably quick here because the piston will slowly want to come forward. Stick a small amount of copper grease on the thread of your sliding pins and placed them back. Before you fully tighten either of them, It’s best to have both in and screwed up a certain amount.
Don’t massively over-tighten these. Put any end caps there could have been back on. Pump the brake pedal a few times, then push down hard. As there’s no engine running it should feel solid rather than sink down.
If it does sink down then you’ve got air in your need and system to get it checked. This really is however a really rare occurrence and very unlikely to happen. If it all feels ok the very last thing is to put the wire back on. Best option is to secure one end first, then use a set of pliers to obtain the other end in. Once it’s directly into bed it against the carrier and caliper have a gentle tap.
You should now see such as this:
New discs have a thin protective film of oil and you will have likely got grubby fingermarks everywhere in the disc so use a cloth and wipe it off as best it is possible to.
Remove any wheel nuts you could have used to contain the disc into position if all is well. Put a little bit copper grease on the face of the disc that will be touching the within the wheel. Provide you with the wheel up, and do not rotate the disc if it’s not secure from a screw. Tighten your wheel nuts handy tight then half a turn, then lower the car down and tighten fully.
Give yourself a pat about the back then crack on with one other side. Don’t forget to set the brake fluid reservoir cap back on and clean up any brake fluid spillages.
Once both sides are carried out go for a test drive. The brake pad may feel harder initially, plus your brakes won’t feel as good. Brakes need a chance to bed in before they perform at their best so try to avoid the need to brake quickly from high-speed.
Try not to brake harshly for a few hundred miles as repeated hard braking on new discs can sometimes warp them and they’ll have to be replaced again. You may also notice a slight hot oil smell as you leave the car, this will be any residue burning off the disc. You don’t need to be concerned unless it doesn’t disappear after several drives.
That’s all there is certainly to it. Best of luck. This post was created by Guy Heaton.