Difference between brake discs and brake pads?

armabelle

I drive a Kia Rio 2012 and the caliper seized so I took it into the dealer as it is still under warranty. They replaced the caliper but said I also needed my brake discs and brake pads changed. Could someone help me understand the difference please? And are brake discs also a "wear & tear" part on a car? I thought only brake pads are what need replacing after a certain period of time.

thank you!

Alun

If a brake caliper seizes, especially if it isn't caught early, then the disc can overheat and warp. Pads are usually changed at the same time as discs anyway as a matter of course, but in the case of a seized caliper they will also probably have become worn down due to excess friction.

Jimmy Garlic

Brake discs are the silver things you see just behind your wheels:D They do wear out and need replacement. That won't be covered by the warranty as they are consumable parts.

punisher5112

Make sure disc and pads are changed on both sides of the same axle.

alpha13

brake pads are the friction material that meshes with the brake disc to slow you down. the brake disc is the actual disc(silver metal) you see when you look in through the wheel... it is metal but does wear with use and time. generally you would replace a few sets of pads before you do the disks..again driving conditions dependant on how long they will last... hard braking will naturally increase the wear rate not to mention overheat the brakes..leading potentially to overheating and seizing calipers... and premature wear rate.

CJhaughey

Think of the brake disc as a round steel plate attached to your wheel.
The caliper is the metal part that holds the discs in place and the pads are the pieces that actually squeeze the disc to slow the car down.
Brake pads are wear items but the disc also wears usually at a slower rate because of the material its made from and the size of it.
If the caliper has seized the pads will contact the disc and can prematurely wear the disc and also warp it from excess heat.

Isambard

that's still not a clear description, so I'll have a go

The calliper is a device which contain the brake pistons. When the brake is applied , these pistons force the brake pads, which are held in the calliper, against the brake discs which are attached behind the wheel, creating friction and thus slowing the car. The pads and the discs are thus both wear items and won't be covered by a warranty

biko

https://www.youtube.com/watch?v=s2egqlckeO4

anthony4335

Becoming a very common problem as far as I can see. I have a 09 Prius and had to replace one this year with only 75k miles on the clock, my parents 07 ceed with just over 60k had both front ones replaced and I have heard or friends with newer cars have a caliper replaced. In all the cars I have ever owned before I have never replaced a caliper.

Isambard

it's because of the friction material used nowadays. It's more abrasive because of the change from asbestos containing pads. Discs are not particularly expensive to replace after 60 or 70 thousand kilometre.

If you look at it from the other side of the coin, there was a day when a car was almost finished at that mileage.

Stephenc66

If one disc has been prematurely worn down below the minimum requirements for the safety of the car as a result of a sticking caliper, which has been replaced under warranty. Could a case be made that the discs and brake pads while a wear and tear item should also be covered, or perhaps a contribution made to replacement cost by the manufacturer under warranty?

The wear on both the discs for the axle concerned could be compared to establish if this was the case

ikeano29

Isambard wrote: »

it's because of the friction material used nowadays. It's more abrasive because of the change from asbestos containing pads. Discs are not particularly expensive to replace after 60 or 70 thousand kilometre.

If you look at it from the other side of the coin, there was a day when a car was almost finished at that mileage.

What day was that when a car was finished after 60 or 70 thousand km?

grogi

armabelle wrote: »

thank you!

Disc is the... well... silver disc.
Caliper is the gray thing in the left with 096 written on it.
Between the disc and the caliper there are the pads...

--

If the discs and pads worn out and need changing only because of the sticking caliper, I would fight the charge. The premature wear is a direct consequence a malfunction and as such should be covered under warranty as well.

kyote00

That disc needs changing :eek:.... more grooves than an old record

grogi wrote: »

Disc is the... well... silver disc.
Caliper is the gray thing in the left with 096 written on it.
Between the disc and the caliper there are the pads...

--

If the discs and pads worn out and need changing only because of the sticking caliper, I would fight the charge. The premature wear is a direct consequence a malfunction and as such should be covered under warranty as well.

mickdw

Unless the disc and pads on other side of the car are worn too, they will have to replace the whole lot under warranty.
Unfortunately, main dealer wear limits are very much on the safe side so they will most likely be able to argue that the other side is also at wear limit and make you pay when in reality there was possibly alot of use left in it

Jesus.

My rear brakes are sticking. You can hear them screeching when you reverse with the window down and if you leave it out of gear on a hill it won't roll back. Is that my pads, discs or caliper that need doing?

armabelle

Isambard wrote: »

it's because of the friction material used nowadays. It's more abrasive because of the change from asbestos containing pads. Discs are not particularly expensive to replace after 60 or 70 thousand kilometre.

If you look at it from the other side of the coin, there was a day when a car was almost finished at that mileage.

When was that day? Must have been long ago because my first car was 20 years old when I purchased it in the nineties

armabelle

grogi wrote: »

Disc is the... well... silver disc.
Caliper is the gray thing in the left with 096 written on it.
Between the disc and the caliper there are the pads...

--

If the discs and pads worn out and need changing only because of the sticking caliper, I would fight the charge. The premature wear is a direct consequence a malfunction and as such should be covered under warranty as well.

They did the repair and I paid for it already but they gave me a 20% discount (240 euro for back break pads and discs). I asked them for my old parts and asked the man to show me where the reason was that the brake discs needed replacing because I have never had such a replacement on any car I have owned. He showed me the disc (I believe it is also called the rotor) and said that it was worn in and there was a groove. How do you actually know when a break disc needs replacing, like what are the signs?

colm_mcm

Jesus. wrote: »

My rear brakes are sticking. You can hear them screeching when you reverse with the window down and if you leave it out of gear on a hill it won't roll back. Is that my pads, discs or caliper that need doing?

Calliper most likely. It should be retracting when you're off the brakes.

Voodoomelon

armabelle wrote: »

They did the repair and I paid for it already but they gave me a 20% discount (240 euro for back break pads and discs). I asked them for my old parts and asked the man to show me where the reason was that the brake discs needed replacing because I have never had such a replacement on any car I have owned. He showed me the disc (I believe it is also called the rotor) and said that it was worn in and there was a groove. How do you actually know when a break disc needs replacing, like what are the signs?

The main sign is an excessive lip on the edge of the disc, indicating the whole face of the disc has worn down where the pad rubs against it. The lip on the edge of the disc remains as the pad does not contact this area.

This level of wear is subjective and one garage will tell you to replace it when another won't. Other reasons to replace the disc as mentioned above are if it's warped (which can be hard to see with the naked eye) or if it's corroded.

armabelle

Voodoomelon wrote: »

The main sign is an excessive lip on the edge of the disc, indicating the whole face of the disc has worn down where the pad rubs against it. The lip on the edge of the disc remains as the pad does not contact this area.

This level of wear is subjective and one garage will tell you to replace it when another won't. Other reasons to replace the disc as mentioned above are if it's warped (which can be hard to see with the naked eye) or corroded.

There is a lip as you say on the disc but who can say if this is because of general wear & tear or because of the caliper seizing. How can I proove this?

Voodoomelon

You can't. And to be honest, its not worth even fighting for. If there is a very noticeable lip on the discs, they should probably have been replaced anyway.
How you've never had discs replaced in your motoring life I have no idea, its a very common thing.

GerryDerpy

There is a spec for minimum disc thickness and it can be measured with a micrometer.

Stephenc66

There is a lip as you say on the disc but who can say if this is because of general wear & tear or because of the caliper seizing. How can I proove this?[/quote]

If there is a lip on the disc with the stuck calliper and not on the other then this is not wear and tear. As Gerry says there is a minimum thickness that can be measured. If one disc is ok and the disc from the seized calliper is not then you have an argument for at least a contribution

It is worth asking

armabelle

Stephenc66 wrote: »

There is a lip as you say on the disc but who can say if this is because of general wear & tear or because of the caliper seizing. How can I proove this?

If there is a lip on the disc with the stuck calliper and not on the other then this is not wear and tear. As Gerry says there is a minimum thickness that can be measured. If one disc is ok and the disc from the seized calliper is not then you have an argument for at least a contribution

It is worth asking[/QUOTE]

I thought about this too. On the one there is definitely more "lip" then the other. Anyway, on both of them, the lip is less than a mm or two. How much lip should there be before changing?

armabelle

GerryDerpy wrote: »

There is a spec for minimum disc thickness and it can be measured with a micrometer.

do you know what the spec is or will it depend on vehicle?

mickdw

I thought about this too. On the one there is definitely more "lip" then the other. Anyway, on both of them, the lip is less than a mm or two. How much lip should there be before changing?

Vehicle specific. 1mm each face could very well be the wear limit set by the manufacturer.
On my car, I looked up the wear limit as specified by the actual disc manufacturer and the wear they deemed allowable was twice what audi were specifying when fitted to my car so as I said earlier, the car manufacturers are quoting very safe wear limits and will likely be able to cover themselves that way.

CJhaughey

Usually quality discs will have a wear limit cast into the disc face.

I have seen vented discs worn right down to the internal ribs in some cases on poorly maintained cars.

*Audi main dealers seem willing to change them sooner than this though at most services.

afatbollix

Only one thing that stops you when you need it.

If he guys in the garage said to change the disks and pads I would do it every time.

No need to skimp on it.

colm_mcm

I've seen discs being recommended to be replaced far earlier than is necessary. I agree with you to a point afarbollix, but if a garage told you you should get 4 new tyres, would you automatically buy them?

mickdw

afatbollix wrote: »

Only one thing that stops you when you need it.

If he guys in the garage said to change the disks and pads I would do it every time.

No need to skimp on it.

I hope you are not a customer of certain franchise outlets as you may find yourself paying a bill for 4 tyres, brakes all round and a couple of shocks every time you go in for a light bulb