Retro-fitting ceramic brakes

[Teutonic_Tamer]

But if you use your standard brakes hard enough to induce brake fade, then the ceramics would be a worthy option!

You would really need to use the brakes abnormally hard to induce fade in ordinary track day use or even amateur racing if you have a decent pad/disc/hose/fluid setup. This is also assuming you do include some cool-down laps. It would be an indication of lack of driving skill/knowledge of the track. I've never once managed to induce brake fade in any of the setups I've tracked previously... an Evo VIII, M3, civic type-R and mini...and believe me, I tracked them hard!

Hmmmm . . . . I am regularly able to induce fade on my S4, and regarding "track action", I have never been advised of any lack of driving skill.

Just to add a little more info, I usually use "airfield" tracks, rather than the more conventional race circuits. On the airfield circuits, you are able to reach much higher speeds, and so, braking from those higher speeds, to negociate very tight chicanes, then there is much more engery to dissipate.

Furthermore, the S4 is quite a heavy car, with a kerb weight of 1755kg. On the track, the weight will be around 1835kg, and during road use, in the south of France, with the car fully loaded, the weight will be around 2100-2200kg! That is an awful lot of kinetic energy!

I would guess that your cars are considerably lighter than my S4?

Braided hoses only affect the "feel" of the brake pedal, rather than improving brake performance. The braiding merely prevents the "balooning" effect that can occur on rubber flexy hoses, under very high pedal pressure.

...they do affect braking performance because they allow for more precise braking "feel" and less pedal travel to induce the same braking force repeatedly, compared to a balooning rubber/flexible hose. Hence they provide less variability in braking force and pedal travel from the beginning to the end of a track/race session. You need to remember, braking performance is not simply thought of as a one-dimensional measure...i.e. how fast or in how short a distance can I stop. The feel/precision and travel of the pedal are equally as important.

Hmmm, again, I have to slightly disagree. Braided hoses do not provide any increase in brake effect. They merely maintain consistency. Agreed, the actual pedal "feel" may be improved, but that, per se, does not increase the braking effect which is generated between the disc, the pad, and the tyre!

High quality brake fluid won't prevent brake fade. The higher boiling point will reduce the likelyhood of vapour lock, though, but standard DOT 4 has a pretty high boiling point, and provided the standard fluid is changed, ideally every year, at most 2 yearly, it is unlikely to suffer with vapour lock.

I agree it won't prevent fade, but it will darn well make a huge difference to your braking performance and the consistency of this performance. There is huge variability in the 'wet' boiling points of DOT 4, DOT 5 and DOT 5.1. Dry boiling points do not give you any idea of longevity of the fluid or the likelyhood of vapour lock. That is a function of wet boiling points and using a high wet boiling point fluid will result in less water absorption, less vapour lock and hence more consistent braking performance for longer with less likelyhood of a "mushy" pedal feel. Castrol SRF has pretty much the highest wet boiling point of any brake fluid by quite a long way...although you do pay for it.

I don't disagree with your points you make. However, I do take issue with the wet boiling points. Any brake fluid which is changed on a regular basis should never actually get anywhere near the "true" wet boiling points. All the benefits that Castrol SRF offer, would be easily countered by slightly more frequent brake fluid changes, using the "lesser" DOT 4 fluid.

Now please don't shoot me down in flames for this next comment. I do know that SRF is a very good product, and it does have an extremely valid use in certain extreme applications. However, I do find that it is primarily sold with a certain kind of "snake oil" mentality, along with DOT 5, when, for the vast majority of sales, it actually offers no advantage over conventional DOT 4.

The specification of the pad material is the major contributoring factor to cause brake fade. It is a problem that plagues my current B6 S4, which is why I specced the Ceramics on the RS4.

I agree...I'm still not sure what pad material comes as standard on the RS4

Agreed, and based on my S4 experiences, and those of current RS4 owners who suffer brake fade with track use, I thought the Ceramics would be a no-brainer.

[alex_123_fra]

Hmmmm . . . . I am regularly able to induce fade on my S4, and regarding "track action", I have never been advised of any lack of driving skill.
Just to add a little more info, I usually use "airfield" tracks, rather than the more conventional race circuits. On the airfield circuits, you are able to reach much higher speeds, and so, braking from those higher speeds, to negociate very tight chicanes, then there is much more engery to dissipate.

Furthermore, the S4 is quite a heavy car, with a kerb weight of 1755kg. On the track, the weight will be around 1835kg, and during road use, in the south of France, with the car fully loaded, the weight will be around 2100-2200kg! That is an awful lot of kinetic energy!

I would guess that your cars are considerably lighter than my S4?

Sorry if that came across wrongly...didn't mean that you specifically lack driving skill. Just that generally regular brake fade on a track may be symptomatic of very high overuse of the brake pedal. I tend to be quite sympathetic even on track with my use of the brakes and try to be progressive rather than slamming on them. I agree the type of car you drive will have huge bearing on this. The heaviest car I drove was the M3 and I suspect the S4 is even heavier than that. Using airfield tracks magnifies the above, as you say, due to the higher speeds.

Hmmm, again, I have to slightly disagree. Braided hoses do not provide any increase in brake effect. They merely maintain consistency. Agreed, the actual pedal "feel" may be improved, but that, per se, does not increase the braking effect which is generated between the disc, the pad, and the tyre!.

I completely agree the hoses won't increase brake effect. I guess what I was trying to say is that in my view, braking performance is not simply a function of stopping distance alone. I look at it as a combination of stopping distance/pedal feel, consistency and precision. I drove a GT3 RS a while ago with a CC set-up and it felt very all-or-nothing to me which didn't do my driving any favours. I suppose it is something one gets used to.

Now please don't shoot me down in flames for this next comment. I do know that SRF is a very good product, and it does have an extremely valid use in certain extreme applications. However, I do find that it is primarily sold with a certain kind of "snake oil" mentality, along with DOT 5, when, for the vast majority of sales, it actually offers no advantage over conventional DOT 4.

Yes, granted. I could probably think of a few automotive stores who sell it/promote it to people who don't actually need it. I did however find that it was far superior to the ATE super blue that I used to usee in terms of not needing to change fluids quite as often and achieving consistency. Again, I guess down to personal taste/experience.

Overall, I would buy a second hand RS4 with the CC brake upgrade but I would still not spec it in a new car. I hope you have fun with it...it'll certainly be a formiddable machine on the track!

[Teutonic_Tamer]

Hmmmm . . . . I am regularly able to induce fade on my S4, and regarding "track action", I have never been advised of any lack of driving skill.
Just to add a little more info, I usually use "airfield" tracks, rather than the more conventional race circuits. On the airfield circuits, you are able to reach much higher speeds, and so, braking from those higher speeds, to negociate very tight chicanes, then there is much more engery to dissipate.

Furthermore, the S4 is quite a heavy car, with a kerb weight of 1755kg. On the track, the weight will be around 1835kg, and during road use, in the south of France, with the car fully loaded, the weight will be around 2100-2200kg! That is an awful lot of kinetic energy!

I would guess that your cars are considerably lighter than my S4?

Sorry if that came across wrongly...didn't mean that you specifically lack driving skill. Just that generally regular brake fade on a track may be symptomatic of very high overuse of the brake pedal.

Oh, no worries, and no offence taken. I usually have the skin of a Rhino!

I'm actually quite receptive to constructive criticism, particularly when getting around a track quicker!

I tend to be quite sympathetic even on track with my use of the brakes and try to be progressive rather than slamming on them. I agree the type of car you drive will have huge bearing on this. The heaviest car I drove was the M3 and I suspect the S4 is even heavier than that. Using airfield tracks magnifies the above, as you say, due to the higher speeds.

I think you are probaly correct. I have always been quite a heavy user of brakes, and whilst I never actually slam hard on the pedal, I am usually progressive, but with high pedal load. I guess my pedal pressure, plotted on a graph, would look like half an upside down sine curve, with quite a steep amplitude!

Sadly, with the heavy weight of the S4, and much of that weight being ahead of the front axle, I tend to trail-brake into corners, and often jab at the brakes to upset the rear end, and try to get some rear end steering. It doesn't always look too elegent, but it seems to work, and another chap with a stripped out and caged M3 has "difficulties" with me!

Hmmm, again, I have to slightly disagree. Braided hoses do not provide any increase in brake effect. They merely maintain consistency. Agreed, the actual pedal "feel" may be improved, but that, per se, does not increase the braking effect which is generated between the disc, the pad, and the tyre!.

I completely agree the hoses won't increase brake effect. I guess what I was trying to say is that in my view, braking performance is not simply a function of stopping distance alone. I look at it as a combination of stopping distance/pedal feel, consistency and precision. I drove a GT3 RS a while ago with a CC set-up and it felt very all-or-nothing to me which didn't do my driving any favours. I suppose it is something one gets used to.

OK, I think we have cleared that one up!

Your comments on the GT3 sound interesting - would that be the general concensus, or would it just be your personal opinion? Not actually having the luxury of trying the Ceramics, I just took the plunge, ordering blind!

One thing I am slightly confused on - you refer to the GT3 as CC - would that actually mean a Carbon/Ceramic composite? I'm sure the RS4 are a Ceramic only construction, though I'd be pleased to learn more!

Now please don't shoot me down in flames for this next comment. I do know that SRF is a very good product, and it does have an extremely valid use in certain extreme applications. However, I do find that it is primarily sold with a certain kind of "snake oil" mentality, along with DOT 5, when, for the vast majority of sales, it actually offers no advantage over conventional DOT 4.

Yes, granted. I could probably think of a few automotive stores who sell it/promote it to people who don't actually need it. I did however find that it was far superior to the ATE super blue that I used to usee in terms of not needing to change fluids quite as often and achieving consistency. Again, I guess down to personal taste/experience.

Looking again through my own collection of data, is the SRF a DOT 5, as I see it is a silicone base? If so, then that would mean a complete flush from any glycol based DOT 4 or 5.1.

What sort of timescale do you use for fluid changes, if you don't mind me asking?

Overall, I would buy a second hand RS4 with the CC brake upgrade but I would still not spec it in a new car. I hope you have fun with it...it'll certainly be a formiddable machine on the track!

You'll have a long wait for mine to be available!

I've still not talked SWMBO into tracking the RS4 when I get it - looks like a new frock and shoes will be required !!!! (for her, not me!)

[alex_123_fra]

Your comments on the GT3 sound interesting - would that be the general concensus, or would it just be your personal opinion? Not actually having the luxury of trying the Ceramics, I just took the plunge, ordering blind!

One thing I am slightly confused on - you refer to the GT3 as CC - would that actually mean a Carbon/Ceramic composite? I'm sure the RS4 are a Ceramic only construction, though I'd be pleased to learn more!

The GT3 I tried had the standard PCCB...carbon-ceramic composite brakes. I haven't driven another car with carbon ceramic brakes to enable me to compare, but these felt totally different to what I was used to. One thing which may cloud the issue... porsche have had huge problems with failing/overheating PCCB discs and numerous warranty claims...some of which are not honoured. I may have been driving a car with duff discs. Some owners have had PCCB discs fail at under 20k miles without track use! An example here:

http://www.stuttgartnines.co.uk/upload/ ... an%20style

I believe they are getting better however. A big danger is thinking that simply because they will resist fade so much, they won't overheat...but the failures suggest they do overheat. Again, it is down to how they are used.

As far as what composes the audi carbon-ceramic discs, I thought they were composites too as per this site, but I'm no expert on it:

http://www.audi.com/audi/com/en2/tools/ ... ramic.html

What seems to be encouraging though is that with the effort audi/porsche/ferrari etc are putting into ceramic brake technology, the prices are coming down all the time. They seem to think that within the next 5 years we might be getting towards half the price that they cost now due to the increased production.

Also here is a useful test I dug up between ceramics and standard discs comparing 2 RS4s with respective discs and their stopping distances plus a similar comparison in a 997 carrera S:

http://www.6speedonline.com/forums/show ... hp?t=74125

Interesting to note the consistency of the ceramics in the RS4 test. The big reds did well on the carrera S except for sustained performance on the track...which is where the ceramics shine.

What sort of timescale do you use for fluid changes, if you don't mind me asking?

On the ATE super blue, it used to be every 6 months. With the SRF, it stretched to over a year but then I bottled it and changed the fluid anyway, even though I probably didn't need to

You'll have a long wait for mine to be available! ?

...I had a feeling that would be the case. I'll be looking into getting a second-hand RS4 in the next 2-3 months. I'm stuck in this cycle at the moment when I know I need a bigger more practical car than my Noble but every time I go for a drive in it...I end up saying "let's wait a bit longer" as I get addicted to it all over again. It is driving my wife nuts. RS4s are stunning though and I know I will be pleased to have one as a family car.

[Andyuk911]

Easier to read :-

Ceramic brake
Compared with conventional steel discs, ceramic brakes not only last four times longer, but also offer high braking performance, even when driving at the limit, as well as high resistance to fading. Braking performance is not diminished even after repeated braking, when driving down a mountain pass, for example. The unsprung rotating masses at the wheels are reduced by a total of around 20 kilograms or 50 percent compared with conventional brake discs, resulting in noticeably improved handling and agility.

Audi ceramic brake discs are made from a carbon fibre-reinforced ceramic. The raw material used to make this compound – known as composite ceramic – is the very hard and abrasion-resistant silicon carbide. High-strength carbon fibres are embedded in it, and these effectively absorb the stresses occurring in the material. Compared with an identical brake disc made of steel, this material lasts four times longer: the high abrasion resistance of ceramic discs means that they will last for up to 300,000 kilometres. The extreme surface hardness of the composite ceramic also means that the brake discs are unsusceptible to solid and liquid road salts as well as to corrosion and rust.