Brake Servicing (Disks, Pads and Fluid)

Pads, Disks, and Fluid are the 3 elements of a braking system that you can guarantee will be replaced in a car's life. They last about 20-50K, 40-100K, and 2 years respectively so any car more than a few years old isn't unlikely to have had all 3 replaced. Unlike most other car parts, the majority of the Braking system doesn't age significantly with time. Pads and Disks however will last almost forever until they're worn out.

Pads and Disks should always be replaced in axle pairs to prevent differences between the left/right side of the car. If one side brakes better than the other, the car could turn when you apply the brakes. Generally a pair will wear out at the same time also, so it makes sense.

Many companies make brake parts, generally, Mintex and Apec are decent quality parts and they're availalbe for the majority of cars. You do not need to go for OEM.

In this article, you'll learn how to work on these major parts, as well as when, and if you should consider uprated parts.

Parts

Pads

Pads are quite a bit like tyres - they're made of a soft material and their purpose is to be very grippy. They're pushed into the Disks by the calipers, which slows them and in turn the car down. However, their soft nature makes them prone to wear, with them only lasting a few dozen thousand miles in most cases.

When to replace pads

Pads don't "age" like many other car parts. They won't crack like tyres, or rust like many other parts - so it pretty much depends 100% on mileage. Generally, if you have symptoms of pad wear and they're over 20K miles old, they likely need replacement. Consistent squealing when braking, less resistance in the first inch of pedal travel, and reduced performance are the obvious signs. If your brakes squeal even when not braking, that often means the pad is now smaller than the wear indicator which allows it to touch the disk even with no use, and that indicates rapid replacement is needed.

Uprated pads

Uprated pads are pads designed to be more resistant to fade than normal pads. Pads are often the first brake component to overheat and when driving on track OEM pads will often overheat within 30 minutes. There are two main types of uprated pad:

• Road pads - designed for use on the road, they often output OEM performance at ambient temps.
• Race pads - designed for racing only, they don't output good performance until they're several hundred degrees.

You should not use Race pads in a car that drives on the road, as you need to be able to execute an emergency stop at a moments notice, and they won't let you do that. You have to rely on the marketing material and reviews to know what pad fits into which category. Despite the name, road pads are usable for track days and time attacks, and although they're not quite as good as race pads, they're more than enough for 99% of drivers. Both will often create additional disk wear, dust, and noise, but if you get something organic this is limited.

Fluid

Brake fluid is the only part in the braking system that 100% needs replacing after a period of time. All other parts can technically last forever with some effort. Fluid will last about 2 years, or at best, 2 years + however long it takes you to boil the fluid. The issue with Brake fluid is it absorbs water, and water boils at 100C. Eventually you reach a point where you can boil the brake fluid, which creates air in the brake lines and maeks the pedal unresposnive.

When to replace Fluid

Follow the schedule in your manual if possible. Otherwise, poor fluid usually causes a poor pedal response and feel. If the pedal is soft all the way to the floor, that's a good indication your fluid needs bleeding at the least. Sudden pedal movement is also a sign.

Uprated Fluid

Fluid that significantly exceeds the DOT requirements and is often marketed as performance/racing fluid is readily availbile for essentially all cars. Get a DOT that is compatible with your car and look for something with as high a boiling point as possible. Unlike pads there's no downside to using performance Fluid on the road other than the price - but still, most cars can be filled with Motul RBF fluid for £30.

Disks

Disks last longer than the other parts listed here, thanks to the fact they are basically big, thick... disks... of metal. They'll often last 100K miles and age very well too, although rust can temporarily interupt their function if they're unused for long enough - in the winter, it might only take a day.

When to replace Disks

Disks aren't as obvious as the other two, since they wear so slowly any changes in their function can often go unnoticed. You have to physically inspect them and consider their mileage. Check the thickness, and check the surface feels smooth to the touch (don't do that after driving of course...).

Performance Disks

Performance disks come in a few forms, Slooted, Drilled, and Grooved being common ones. They all have the same major pro and con - the pro being they cool themselves and the pads better, the con being they wear the pad quicker. 99% of people, even most track drivers, don't need performance disks, as disks are quite hard to overheat. You only really need them if you drive a heavy, fast car on track. Something like a BMW M.

Requirements

Generally only basic hand-tools and knowledge are needed, however, there are some things specific to brakes you will require, although they're cheap. You'll need:

• A way to safely lift at least one wheel (Minimum Jack + Jackstand)
• The torque specs for the wheels
• Any locking nut sockets
• A larger (1/2") torque wrench caqpable of torquing wheels
• A smaller wrench
• Decent Grease. I use Copper
• A brake bleeder kit
• An open ended wrench that can fit on your bleeder valve
• Something to push the caliper in with. Some poeple use any old clamp, I recommend a brake windback tool

You should also consider, but may get away with not having:

• A way to safely lift an axle (Minimum Jack + 2 Jackstands)
• The torque specs for all of the bolts you'll be removing, typically, bottom caliper bolts, a line bolt, and a handbrake cable bolt in the rear(s)
• A breaker bar
• A smaller torque wrench
• Pliers
• Penetrating fluid
• Wire Brush
• Thick Zipties
• Brake cleaner
• Rags
• Rust converter

Dissasembly

I am not a professional mechanic and haven't seen many cars. Although I believe these instructions will apply to many cars, you should look for information specific to your car as well as this.

If you're doing all 4 wheels, start with the one furtherest from your brake resivour. You should change brake fluid when doing any other brake work, but if you only want to change brake fluid, read "Wheels" and then skip to that section.

Wheels

Check the handbrake is on, and block of the wheels on the axle you're not working on. Use a large wrench/breaker to crack the wheel nuts. If your only large wrench is a torque wrench, set the torque much higher than the spec for the nuts. You will need the locking nut key for the locking nut, and there's likely a cover you need to remove. Many cars come with a tool for this, but if you don't have one, Pliers usually work. Turn the nuts roughly between 90 and 180 degrees.

Once all nuts on the wheels you want to work on are loose, turn the handbrake off if you're working on the rear, and lift the car. If using a jack, place it on a jacking point, typically this is just behind the sill. Lift the car high enough to slide a Jackstand underneath - you don't need much room so leaving the stand at its minimum height should be fine. Place it as close to the jacking point as possible. Lower the car onto the Jackstand. Check the car is lying flat on the Jackstand. Repeat for all relevant wheels. You don't have to do them all at once.

With the wheel lifted, remove the nuts entirely - it's likely they'll be free spinning and sometimes they're removable by hand. Remove one at a time and hold the wheel whilst removing the last one. Then, pull the wheel off. I recommend storing it under the car, then placing one nut back on a lug, and the rest in their slots in the wheel so they don't get lost.

Pads

Firstly we need to loosen the brake line (and cable if working on the rear) so we can easily move the caliper around. There is usually a bolt attaching it to the shock tower. It may need significant penetrating fluid to come loose - if you encounter this, consider spraying all of the corners you haven't done to get a headstart whilst waiting for the one you're working on to loosen up. Don't just spray and prey, it often takes a few minutes to work. You don't always have to remove it fully, loosening it can create enough play in the line to do what we need.

If you're working on the rear, there will be something similar attaching the handbrake cable to the caliper via a bracket. Do the same for that also.

With those undone, start undoing the bottom bolt on the back of the caliper. Be careful of the rubber boot. Once that is removed, try to open the caliper by pulling it away from the disk. If it's stuck, I like to shove the handle of a wrench into the hole used for inspecting the pads - and then pry it open. Once the caliper is open, you need to push the top off of the top slider pin by pushing it further into the wheel well. Wiggling left/right helps also. It will take some effort.

Once the top of the caliper is seperated, try to find somewhere to put it that doesn't stress the line/cable. You may need to hang it somewhere with zipties. If the caliper took an extreme amount of force to seperate, or if it took a lot of effort and then suddenly came loose, consider applying grease to the now exposed top pin.

Now we can remove the pads - this is easy. You can typically just pull them out. There may be some clips, be careful not to break them.

Disks

To get at the Disks, you need to remove the remaining piece of the Caliper. This usually involves two bolts on the rear. Again, these may need some help to come off. Once they're removed, you can pull the Caliper support off, and the brake disk will just come off (If you put a nut on a lug, be sure to remove it ;) )

Assembly

Disks

Simply place the new disk on the lugs, then place the Caliper support in place and do up the bolts. Consider placing a nut on a lug, to hold it in place whilst you put everything else back.

Pads

The piston inside of the caliper defaults to a position where it is just pressing on the pads, but not enough to apply the brakes. Since we've removed a thinner, worn pad, the piston will be too far out for the thicker, new pad. We have to push it back into the caliper. Some people do this with any old clamp or even the handle of a tool, but I highly recommend a wind back kit as it's much easier and fairly cheap. Insert the tool into the caliper with the bottom on the caliper. If there are slots, insert the notches on the windback tool into them. Undo the nut until the bracket hits the inside of the caliper and it's tight.

Attach a tube, preferable a bleed kit with a one way valve, to the bleeder nipple, and undo it slightly. Then, use the handle to push the caliper in by turning it clockwise. Some calipers will also have slots that need to be a certain position - a windback tool will also rotate the piston allowing you to get this right. As you push the piston, some brake fluid will come out of the nipple. Once it's impossible to move any further, remove the tool. You may need to use the nut with a spanner to loosen the tool for removal. Tighten the bleeder nipple.

Now you know for sure they'll fit, clean any mating surfaces with a wirebrush, cloth, and parts cleaner, fit any shims to the pad via clips or adhesive, and insert the pads into the caliper support exactly like the old ones. Consider greasing the top/bottom mating surfaces where the pad slides back and forth. Grease the shim on the back of the pad.

With the pads in, reinsert the top pin into the caliper and start pulling it back into place. If this is very difficult, apply grease to the top pin. Once it's back on, push the bottom pin as far in as possible and check if the caliper will close properly. If it doesn't, the pin is likely seized. Pull it out with Pliers - take care of the boots - clean off any dust/rust if present and apply grease to it, then insert it again. It should go all the way in now.

Place the caliper back into place, and reinstall the bolt. Then reinstall any loosened lines and cables, and you're done.

Fluid

It is advisable to change the Fluid after any work, but it can also be changed by itself with the only dissassembly needed being the wheel removal.

Place a brake bleeder kit with a one way valve on the bleeder nipple, and then undo it. Make the resivour accessible. Go into the car and slam on the brakes repeatedly for about 10 seconds - the force should be comparable to normal (with the car off), except here it'll be possible to push the pedal to the floor repeatedly. After 10 seconds, check the resivour and top off if near the min mark. Go to the bleeder kit and check the tube. The tube should be almost clear with no bubbles near the bleeder nipple. If that isn't the case, try again until it is. This is only technically needed for wheels you've worked on, but it can be worth doing all 4.

Wheels

Remove and wheel nuts if you're using them to hold the disk, and place the wheel on the lugs. Do up the nuts hand tight, then use a wrench to get them as tight as possible before the wheel rotates. If you have finished with the currently raised wheels, raise the car slightly so that the(a) jackstand comes loose, then remove it and lower the car (repeat until all are removed). Using a large torque wrench, torque the wheel(s).

Post Replacement

If you worked on the rear, it isn't a bad idea to keep some wheels blocked off for now. The main thing to be aware of is the brake performance is likely poor, including the handbrake if you worked on the rear, and will be for a few dozen miles, or possibly a few hundred if new pads were fitted to used disks or you're using higher performance pads. Immediately after replacement, get in the car and apply the handbrake fully several times. This will allow it to adjust. It isn't a bad idea to leave it in gear for a day or two. When you first use the car, with the engine on, fully apply and hold the brakes for several seconds, several times. Once you set off, test the brakes as soon as possible to ensure you're able to stop in OK time.

All brakes benifit from bedding in, but performance pads, and pads with used disks, especially benifit. Bedding in just happens but can be greatly accelleated by intentionally heating the parts up and using them whilst they're hot. Do not do this if you haven't at least driven a few miles and come to a stop a few times. Make sure they work. Go to a 60mph road, check behind you, and then hit the brakes until you loose 20-40mph. Do this about 5 times, then continue to your destination as normal. Consider doing it 2 or 3 times total.

As they bed in your pedal should get firmer and performance will improve. The handbrake will also improve. After 50 miles, check the torque of the wheels and try pushing the car with the handbrake on about 3/4. If it moves, apply the handbrake a dozen times and consider applying it whilst the car is rolling backwards. If it still moves, there may be an issue. It isn't uncommon for the handbrake lever to become and remain looser than before on older cars - it's likely it was slightly seized due to rust and you have accidentally removed that. If it works, it's OK.

Notes

• 07/10/2024 - Page populated.

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