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Carbon Discs
MikeFellows - 16/1/12 at 04:41 PM

as a lot of people are always trying to reduce weight, nobody ever seems to mention carbon/ceramic brake setups. I appreciate the costs (not that I know them, but imagine they are high)

I presume you need special pads, but are special calipers required?

what sort of weight saving could be had in a like for like scenario (or are smaller disks a possibility because of improved performance)?

Before anyone asks im not considering this at all, im just putting it out there for peoples thoughts

loggyboy - 16/1/12 at 04:48 PM

YOu need lots of heat, that 600kg cars traveling at 30mph dont generate!

[Edited on 16/1/12 by loggyboy]

tegwin - 16/1/12 at 05:03 PM

You will find that most people with road cars WAY overdo the brakes.... Vented, oversize rotors, 4 piston calipers.

In reality, the single pot sierra calipers on solid disks would be more than enough if you spec the correct master cylinder. You only start to run into issues if you are racing and getting the brakes very hot..

As above though, for ceramic brakes to work you need HEAT. Something you will never manage on a lightweight car.

MikeFellows - 16/1/12 at 05:12 PM

if the discs where smaller, would it not be easier to generate the necessary heat?

fullpint - 16/1/12 at 05:20 PM

I don't think so. Ok yes smaller disc would heat up a little quicker but not enough inorder to generate the heat for the pads to work.
I presume you are thinking about fitting them to your Indy?

MikeFellows - 16/1/12 at 05:50 PM

no not at all, i was just trying to get an understanding as to why nobody has considered them

Ive got some wilwoods with solid disks and mintex pads

onenastyviper - 16/1/12 at 06:11 PM

F1 car weighs ~650kg and they use carbon carbon easily.
The problem with carbon/ceramic brakes is that the modulation is virtually non-existant when cold, they tend to either be off or locked up. As previous posts mention, heat is required although does beg the question how have porsche etc. managed to use carbon or ceramic compounds in their high-end brakes - is it just a bit of overselling I wonder?

Oh, I forgot to add that the heat is generated from the kinetic energy so unless you are planning to stop from 200kph+ often, they probably won't work well.

Funny story - lad at uni decided for his final year project to investigate carbon brakes so he fitted a carbon disk to his race cart. Took it to Three Sisters in Wigan to test it and he said he set a record for the number of 180degree spin turns as whenever he pressed the brake, it locked up...not my idea of fun.

[Edited on 16/1/12 by onenastyviper]

MikeFellows - 16/1/12 at 06:12 PM

quote:
Originally posted by onenastyviper
F1 car weighs ~650kg and they use carbon carbon easily.
The problem with carbon/ceramic brakes is that the modulation is virtually non-existant when cold, they tend to either be off or locked up. As previous posts mention, heat is required although does beg the question how have porsche etc. managed to use carbon or ceramic compounds in their high-end brakes - is it just a bit of overselling I wonder?


forgive my ignorance/stupidity but what do you mean by modulation

designer - 16/1/12 at 06:18 PM

Why would you want carbon brakes??

MikeFellows - 16/1/12 at 06:20 PM

quote:
Originally posted by designer
Why would you want carbon brakes??


read my post, I dont - im just trying to understand why nobody does it

onenastyviper - 16/1/12 at 06:21 PM

quote:
Originally posted by MikeFellows
quote:
Originally posted by onenastyviper
F1 car weighs ~650kg and they use carbon carbon easily.
The problem with carbon/ceramic brakes is that the modulation is virtually non-existant when cold, they tend to either be off or locked up. As previous posts mention, heat is required although does beg the question how have porsche etc. managed to use carbon or ceramic compounds in their high-end brakes - is it just a bit of overselling I wonder?


forgive my ignorance/stupidity but what do you mean by modulation


Modulation is the ability to adjust the braking performance by varying the pressure on the brake pedal.
Brakes have a coefficient of friction (mu) and this can change when the brakes become hot so instead of being almost like a light switch, the heat modifies the friction (mu) and so a level of controllability is introduced.
I suppose the word "hot" can be misleading, I should have stated "within the normal operating temperature". Hot for one compound cold be too low or too high for a different compound. All brake manufacturers should state the "mu" and temperature window.

MikeFellows - 16/1/12 at 09:56 PM

I did a bit more reading into this and found out most carbon ceramic brakes discs supplied with cars are expected to last the lifetime of the car (as in 100,000 miles). not sure if that applies to pads or not though

but if it did, the £10k option price for a high end 911 could maybe pay for itself (maybe)


edit to add that pads and calipers are no different either apparently.

[Edited on 16/1/12 by MikeFellows]

loggyboy - 16/1/12 at 10:22 PM

quote:
Originally posted by onenastyviper
F1 car weighs ~650kg and they use carbon carbon easily.


But they are using the brakes every few seconds, so the heat is generated and retained. Im sure youve heard the radio transmissions on the warm up lap about getting heat in to brakes and tyres.

Sit on a motorway for 20 mins then try and do an emergency stop and youl soon wish you have plain old steel discs!

MikeFellows - 16/1/12 at 10:24 PM

quote:
Originally posted by loggyboy
quote:
Originally posted by onenastyviper
F1 car weighs ~650kg and they use carbon carbon easily.


But they are using the brakes every few seconds, so the heat is generated and retained. Im sure youve heard the radio transmissions on the warm up lap about getting heat in to brakes and tyres.

Sit on a motorway for 20 mins then try and do an emergency stop and youl soon wish you have plain old steel discs!


the question still remains as to how the oem kit manges what your describing - though i concede most are at least twice as heavy as a f1 car

TAZZMAXX - 16/1/12 at 10:30 PM

quote:
Originally posted by MikeFellows
I did a bit more reading into this and found out most carbon ceramic brakes discs supplied with cars are expected to last the lifetime of the car (as in 100,000 miles). not sure if that applies to pads or not though


Carbon ceramic discs get discussed a fair bit on another forum I'm on as most of the guys are running high horsepower, heavy cars and are always looking for improved stopping. This particular point is a sales pitch by the manufacturers that is not quite correct. Although the pads are worn away at a disproportionate rate by the discs, the discs do in fact degrade and this degradation is measured by decrease in mass rather than physical wear. I don't know the exact science behind it but they do wear.

quote:
Originally posted by MikeFellowsbut if it did, the £10k option price for a high end 911 could maybe pay for itself (maybe)


A lot of Porsche 911 and Audi RS4 owners ditched carbon ceramic discs in favour of iron for track use leaving road use cars to keep them (snob value). They aren't cheap and they aren't the best, especially if it's a road car that goes on track. You can buy a lot of iron discs for the price of ceramic ones. As others have stated, cold modulation is not fantastic although it has improved over the initial offerings.

Neville Jones - 17/1/12 at 11:39 AM

You won't buy a 'carbon' (carbon ceramic as they have always been, and originated on aircraft), for less than £1k, and nearer £1500. You can get a lot of iron discs and soft pads for that.