OEM Ceramic Brakes
10-27-2014, 08:37 AM
#21
AudiWorld Super User
I've heard of many cars that automatically, but very lightly apply the brakes in wet conditions to keep the pads and rotor clear to assist in breaking. I thought I even remember reading it in the A8 manual.
10-27-2014, 09:06 AM
#22
AudiWorld Senior Member
Just to clarify...
there are a few posts in this thread that refer to ceramics being more "powerful", which I don't think is an apt description. For any brake system that is capable of locking the brakes, the limiting factor is not at the disk, but at the tire contact to the road. If your brakes can lock em up, that's as "powerful" as they'll get.
That said, ceramics will reduce unsprung weight, will last longer and will be far more resistant to fade on heavy use--all positives. I would imagine that with the right set up, you might also be able to modulate the brakes better, which could allow you to control the braking action better and perhaps stop better, but we're talking now about serious braking skills that most of us mere mortals do not possess.
That said, ceramics will reduce unsprung weight, will last longer and will be far more resistant to fade on heavy use--all positives. I would imagine that with the right set up, you might also be able to modulate the brakes better, which could allow you to control the braking action better and perhaps stop better, but we're talking now about serious braking skills that most of us mere mortals do not possess.
10-27-2014, 09:15 AM
#23
AudiWorld Super User
I would like to see the source of that information. It definitely sounds like uneducated amateur inventors idea. Can you imagine how much energy would be needed to keep brakes warm and dry with all that carefully designed cooling of the same?
10-27-2014, 09:30 AM
#25
AudiWorld Super User
there are a few posts in this thread that refer to ceramics being more "powerful", which I don't think is an apt description. For any brake system that is capable of locking the brakes, the limiting factor is not at the disk, but at the tire contact to the road. If your brakes can lock em up, that's as "powerful" as they'll get.
That said, ceramics will reduce unsprung weight, will last longer and will be far more resistant to fade on heavy use--all positives. I would imagine that with the right set up, you might also be able to modulate the brakes better, which could allow you to control the braking action better and perhaps stop better, but we're talking now about serious braking skills that most of us mere mortals do not possess.
That said, ceramics will reduce unsprung weight, will last longer and will be far more resistant to fade on heavy use--all positives. I would imagine that with the right set up, you might also be able to modulate the brakes better, which could allow you to control the braking action better and perhaps stop better, but we're talking now about serious braking skills that most of us mere mortals do not possess.
Other two advantages are kinda annulled by required bigger wheels and extremely high maintenance costs. If they make them for 18" wheels it would be a different story.
10-27-2014, 09:52 AM
#26
AudiWorld Super User
Here's better info on how they actually work, from Audi.
There are two good info sources. One is an SSP type document when Audi first released the brakes for the D3 W12 as a Euro option, and then other D3's pretty quickly. Audi USA also did an Audi Technical Updates in July 2011; a set of PowerPoint sort of slides I think they use either in a classroom or some kind of web training. The 2011 materials came up with the then upcoming RS7, plus the R8. I have both for anyone seriously interested.
Meanwhile, here is a description of the wipe function from the July 2011 Audi materials (p. 29):
FWIW, the general description of ceramics are that they are more input sensitive, and the typical first time driver to the car tends to jam them on way too hard. Then if they get seriously wet (the whole wipe function theme above), its more like they retreat momentarily to normal brake feel as opposed to you lose braking or any such thing. That's basically Audi's footnote reference in its SSP material, where they are more cursory on the wipe function.
Apparently the time people actually most typically run into it is after they wash the car, not on the street. The July 2011 materials even show a picture of a Q7 in a car wash. On the street the wipe function is tucked away in the ESP electronics to make it pretty seamless. The Audi set up emphasizes street feel in general, not track use. All of this is kind of technical weeds stuff anyway; if you search the R8 guys are uniformly positive, and the occasional Euro posters here comment favorably on anything but price. If there is a knock, my hunch is it might be some slightly elevated noise--a more aggressive semi-metallic pad. Dust apparently very minimal BTW from owners' experiences.
I don't think there is a materials change or update in any of this either; the pads are organic/semimetallic and the rotor chemistry constant AFAIK. There was a recall early on for the rotor to hat bolts due to some theoretical corrosion issues, so you either ask more questions there or just steer to a later manufacturing date--all the rotors are marked with manufacture dates, starting weight, wear parameters, etc.
To be clear, to the contrary, thinking about it I expect mileage if anything to go up a bit, not down in everyday use. MPG not part of my equation especially, but 20 pounds drops out of rotating mass on each side up front, coming down from 100ish stock on a W12/S8 set up with its 40 pound std. rotors. Weight may drop from calipers too, but that is TBD and also unsprung, but not also rotating. Read for yourself, but it's minimum pressure (presumably below perception level) every 3+ minutes for 2.5 sec. at 40+ MPH and only with wiper function on. Relative to pre and post programming type update for the RS7 generation, notice they seem to have made it more active in one case, and for regular brakes too if I read it right, where there is a wipe every kilometer. That pre-wipe, pre-prep stuff has been around for a while IIRC; seems like I've read it before in various Merc. materials.
You configure the brakes via VAG COM/VCDS like a bunch of other Audi options, so I expect little surprise there either. BTW, also settable for different brakes as I recall if you go from 4.2 to S8/W12 sizing if I remember it, but would need to check.
Meanwhile, here is a description of the wipe function from the July 2011 Audi materials (p. 29):
Brake disc wipe function
New: [ed. note: meaning later design]
From A8 D4 (including Q7 V12)
-Brake disc wipe function is activated if the rain sensor is switched to active (i.e. the intermittent wipe lever must be actuated)
-Brake disc wipe function is deactivated if the interval between wiper activations is longer than 30 seconds, even if the intermittent or rain sensor is active
-Speed at which it is switched on and off (vehicle speed) is the same at 80 km/h
-The wiping interval for GG brakes is every 3 km, and every 1 km for ceramic brakes (i.e. not distance and time-dependent)
Previously: [ed note: as in the D3 set up and presumably at least earlier Euro R8's]
When driving in the rain or snow, the front brake pads are periodically (every 185 s) appliedat minimum pressure (0.5–1.5 bar) to the brake discs for a short period (for approx. 2.5 s).
This process cleans the pads and discs; the responsivenessof the brakes is improved. This process is activated when the windscreen wipers are switched on and the vehicle is travelling at a speed of >70 km/h
New: [ed. note: meaning later design]
From A8 D4 (including Q7 V12)
-Brake disc wipe function is activated if the rain sensor is switched to active (i.e. the intermittent wipe lever must be actuated)
-Brake disc wipe function is deactivated if the interval between wiper activations is longer than 30 seconds, even if the intermittent or rain sensor is active
-Speed at which it is switched on and off (vehicle speed) is the same at 80 km/h
-The wiping interval for GG brakes is every 3 km, and every 1 km for ceramic brakes (i.e. not distance and time-dependent)
Previously: [ed note: as in the D3 set up and presumably at least earlier Euro R8's]
When driving in the rain or snow, the front brake pads are periodically (every 185 s) appliedat minimum pressure (0.5–1.5 bar) to the brake discs for a short period (for approx. 2.5 s).
This process cleans the pads and discs; the responsivenessof the brakes is improved. This process is activated when the windscreen wipers are switched on and the vehicle is travelling at a speed of >70 km/h
Apparently the time people actually most typically run into it is after they wash the car, not on the street. The July 2011 materials even show a picture of a Q7 in a car wash. On the street the wipe function is tucked away in the ESP electronics to make it pretty seamless. The Audi set up emphasizes street feel in general, not track use. All of this is kind of technical weeds stuff anyway; if you search the R8 guys are uniformly positive, and the occasional Euro posters here comment favorably on anything but price. If there is a knock, my hunch is it might be some slightly elevated noise--a more aggressive semi-metallic pad. Dust apparently very minimal BTW from owners' experiences.
I don't think there is a materials change or update in any of this either; the pads are organic/semimetallic and the rotor chemistry constant AFAIK. There was a recall early on for the rotor to hat bolts due to some theoretical corrosion issues, so you either ask more questions there or just steer to a later manufacturing date--all the rotors are marked with manufacture dates, starting weight, wear parameters, etc.
To be clear, to the contrary, thinking about it I expect mileage if anything to go up a bit, not down in everyday use. MPG not part of my equation especially, but 20 pounds drops out of rotating mass on each side up front, coming down from 100ish stock on a W12/S8 set up with its 40 pound std. rotors. Weight may drop from calipers too, but that is TBD and also unsprung, but not also rotating. Read for yourself, but it's minimum pressure (presumably below perception level) every 3+ minutes for 2.5 sec. at 40+ MPH and only with wiper function on. Relative to pre and post programming type update for the RS7 generation, notice they seem to have made it more active in one case, and for regular brakes too if I read it right, where there is a wipe every kilometer. That pre-wipe, pre-prep stuff has been around for a while IIRC; seems like I've read it before in various Merc. materials.
You configure the brakes via VAG COM/VCDS like a bunch of other Audi options, so I expect little surprise there either. BTW, also settable for different brakes as I recall if you go from 4.2 to S8/W12 sizing if I remember it, but would need to check.
Last edited by MP4.2+6.0; 10-27-2014 at 10:51 AM.
10-27-2014, 10:08 AM
#27
AudiWorld Super User
Wheel size...
The rotors are 380mm in front, down from 385. 385's clear OE 18's, albeit super tight. The "problem" is really the Brembo caliper, but to me that's a benefit, not a problem design wise. Brembo calipers are invariably "fat," and more so on the outer/wheel side since they have real pistons there as a true fixed/non floating design.
As another data point with 365 RS5 conventional rotors and Brembo OE calipers on the Q5 now, and starting from OE 19's it had lots of vertical room for the calipers; it was the offset near the hub at the caliper edge that was a bit tight, even with a high 30's ET OE wheel. Can't be sure on 18's for the D3 (happy to test fit when time comes since W12 OE spare is the 18" baseline wheel), but would expect little drama w/ 19's. I run 20's anyway (and ET12 front spacers to boot), and only lighter wheel in OE than the twin 7's are the 19" forged zillion spokers. The std. 18's are actually heavier.
As another data point with 365 RS5 conventional rotors and Brembo OE calipers on the Q5 now, and starting from OE 19's it had lots of vertical room for the calipers; it was the offset near the hub at the caliper edge that was a bit tight, even with a high 30's ET OE wheel. Can't be sure on 18's for the D3 (happy to test fit when time comes since W12 OE spare is the 18" baseline wheel), but would expect little drama w/ 19's. I run 20's anyway (and ET12 front spacers to boot), and only lighter wheel in OE than the twin 7's are the 19" forged zillion spokers. The std. 18's are actually heavier.
Last edited by MP4.2+6.0; 10-27-2014 at 10:11 AM.
10-27-2014, 10:51 AM
#28
AudiWorld Super User
There are two good info sources. One is an SSP type document when Audi first released the brakes for the D3 W12 as a Euro option, and then other D3's pretty quickly. Audi USA also did an Audi Technical Updates in July 2011; a set of PowerPoint sort of slides I think they use either in a classroom or some kind of web training. The 2011 materials came up with the then upcoming RS7, plus the R8. I have both for anyone seriously interested.
Meanwhile, here is a description of the wipe function from the July 2011 Audi materials (p. 29):
And to be clear, to the contrary, expect mileage if anything to go up a bit, not down. MPG not part of my equation especially, but 20 pounds is dropping out of rotating mass on each side up front, coming down from 100ish stock on a W12/S8 set up with its 40 pound std. rotors. Read for yourself, but it's minimum pressure (presably below perception level) every 3+ minutes for 2.5 sec. at 40+ MPH and only with wiper function on. Relative to pre and post update, notice they seem to have made it more active in one case, and for regular brakes too if I read it right, where there is a wipe every kilometer. That pre-wipe, pre-prep stuff has been around for a while IIRC; seems like I've read it before in various Merc. materials.
You configure the brakes via VAG COM/VCDS like a bunch of other Audi options, so I expect little surprise there either. BTW, also settable for different brakes as I recall if you go from 4.2 to S8/W12 sizing if I remember it, but would need to check.
Meanwhile, here is a description of the wipe function from the July 2011 Audi materials (p. 29):
Brake disc wipe function
New: [ed. note: meaning later design]
From A8 D4 (including Q7 V12)
-Brake disc wipe function is activated if the rain sensor is switched to active (i.e. the intermittent wipe lever must be actuated)
-Brake disc wipe function is deactivated if the interval between wiper activations is longer than 30 seconds, even if the intermittent or rain sensor is active
-Speed at which it is switched on and off (vehicle speed) is the same at 80 km/h
-The wiping interval for GG brakes is every 3 km, and every 1 km for ceramic brakes (i.e. not distance and time-dependent)
Previously: [ed note: as in the D3 set up and presumably at least earlier Euro R8's]
When driving in the rain or snow, the front brake pads are periodically (every 185 s) appliedat minimum pressure (0.5–1.5 bar) to the brake discs for a short period (for approx. 2.5 s).
This process cleans the pads and discs; the responsivenessof the brakes is improved. This process is activated when the windscreen wipers are switched on and the vehicle is travelling at a speed of >70 km/h
FWIW, the general description of ceramics are that they are more input sensitive, and the typical first time driver to the car tends to jam them on way too hard. Then if they get seriously wet (the whole wipe function theme above), its more like they retreat momentarily to normal brake feel as opposed to you lose braking or any such thing. Apparently the time people actually most typically run into it is after they wash the car, not on the street. The July 2011 materials even show a picture of a Q7 in a car wash. On the street the wipe function is underneath to make it pretty seamless. The Audi set up emphasizes street feel in general, not track use. I don't think there is a materials change or update in any of this either; the pads are organic/semimetallic and the rotor chemistry constant AFAIK. There was a recall early on for the rotor to hat bolts due to some theoretical corrosion issues, so you either ask more questions there or just steer to a later manufacturing date--all the rotors are marked with manufacture dates, starting weight, wear parameters, etc.New: [ed. note: meaning later design]
From A8 D4 (including Q7 V12)
-Brake disc wipe function is activated if the rain sensor is switched to active (i.e. the intermittent wipe lever must be actuated)
-Brake disc wipe function is deactivated if the interval between wiper activations is longer than 30 seconds, even if the intermittent or rain sensor is active
-Speed at which it is switched on and off (vehicle speed) is the same at 80 km/h
-The wiping interval for GG brakes is every 3 km, and every 1 km for ceramic brakes (i.e. not distance and time-dependent)
Previously: [ed note: as in the D3 set up and presumably at least earlier Euro R8's]
When driving in the rain or snow, the front brake pads are periodically (every 185 s) appliedat minimum pressure (0.5–1.5 bar) to the brake discs for a short period (for approx. 2.5 s).
This process cleans the pads and discs; the responsivenessof the brakes is improved. This process is activated when the windscreen wipers are switched on and the vehicle is travelling at a speed of >70 km/h
And to be clear, to the contrary, expect mileage if anything to go up a bit, not down. MPG not part of my equation especially, but 20 pounds is dropping out of rotating mass on each side up front, coming down from 100ish stock on a W12/S8 set up with its 40 pound std. rotors. Read for yourself, but it's minimum pressure (presably below perception level) every 3+ minutes for 2.5 sec. at 40+ MPH and only with wiper function on. Relative to pre and post update, notice they seem to have made it more active in one case, and for regular brakes too if I read it right, where there is a wipe every kilometer. That pre-wipe, pre-prep stuff has been around for a while IIRC; seems like I've read it before in various Merc. materials.
You configure the brakes via VAG COM/VCDS like a bunch of other Audi options, so I expect little surprise there either. BTW, also settable for different brakes as I recall if you go from 4.2 to S8/W12 sizing if I remember it, but would need to check.
I didn't know about that wipe feature and I still think it is just another Art's gimmick. Wiping brakes every now and than would make them semi dry every now and then and just as wet in between. Warming them enough to stay dry in rain would be ridiculous, extremely uncomfortable, unsafe in traffic and fuel consuming.
As far as I know rotor material for a street use is different (changed) than one for races. Probably compromise making them acceptable when cold and still good enough when hot. Some of them require driver to adjust to a lower friction when cold to increased friction when they warm up. That means more initial pedal force and relaxing it for smooth slowing down. Unprepared driver would apply regular pedal force at the beginning and getting not expected braking panic and push it much more. In the mean time brakes would warm up a bit, increase friction just to brake way too much.
Increasing millage as a result of lowered rotational rotor mass is annulled by bigger wheel moment of inertia (more mass at larger diameter for uneducated readers only
).So, my conclusion is that there are no good reasons for those brakes on any regular car. But I would still like to have them
10-27-2014, 11:04 AM
#29
AudiWorld Super User
It's a hobby of course...
The brakes on the A8 are way beyond any North America road need. Includes the 4.2 to S8/W12 step up by the way on conventional rotors, to be clear too. In researching, I even found even the Euro Phaeton W12 at 420 HP still has the 360mm conventional 4.2 D3 set up, so there it steps up to 380 on ceramics instead of down from 385. And the Phaeton is close to another 1000 pounds of pork over the D3 W12, let alone a 4.2. Its 420 HP in VW (de-)tune, but still well over the 4.2.
Can't be sure of your rotating mass point, but guessing it is tied to 18's vs. 20's where more metal pushes further out on the wheel compared to the rubber height. Agreed. Stock to stock simplicity though, in 18" OE the Audi wheels are not top drawer spec wise. Might still be an amateur track choice--on a different planet of vehicle than D3s--if folks want to use cheaper commodity replacement stuff. Understood on the theory and practice side from the Mini world, where they do get tracked and the basic set up is bigger but typically OE type brakes, more aggressive pad, wider width, smallest wheel that fits.
Can't be sure of your rotating mass point, but guessing it is tied to 18's vs. 20's where more metal pushes further out on the wheel compared to the rubber height. Agreed. Stock to stock simplicity though, in 18" OE the Audi wheels are not top drawer spec wise. Might still be an amateur track choice--on a different planet of vehicle than D3s--if folks want to use cheaper commodity replacement stuff. Understood on the theory and practice side from the Mini world, where they do get tracked and the basic set up is bigger but typically OE type brakes, more aggressive pad, wider width, smallest wheel that fits.
10-27-2014, 12:12 PM
#30
AudiWorld Super User
Hobby of Course
Starting from the best weight, handling, acceleration and braking wise, Formula 1 wheels:
To the next best, Audi Etron Quatro wheels:
It is obvious that smaller rim and more sidewall works best. I can say that from my own experience with 18's and 20's. I would go to 16's if I can get serious brakes for that size.
To the next best, Audi Etron Quatro wheels:
It is obvious that smaller rim and more sidewall works best. I can say that from my own experience with 18's and 20's. I would go to 16's if I can get serious brakes for that size.
