D3 W12 (+S8) rear brakes--out with the old, in with the new (very long)
09-14-2008, 11:16 PM
#1
AudiWorld Super User
Thread Starter
D3 W12 (+S8) rear brakes--out with the old, in with the new (very long)
I did the rear brakes today on the W12. Car has 28,500 miles with original rears. Identical to S8's, and figure it's basically like a 4.2 in back except the rotors are on steroids.
End result:
<img src="http://pictureposter.audiworld.com/26081/img_4053crop.jpg">
Picture 1
1. Degree of difficulty: To the post last week about the >$1,000 rear brake job by a dealer, all I can say now is that is really absurd! It was very easy to do. Among the easiest of any car I have seen in the rear. The hardest part by far was simply finding the right part of Bentley to execute the VAG COM command to release the brakes. If I did it without the paint on the new set up, I would say once the wheels are off it would take one hour with experience and decent tools, no more than two hours even with VAG COM and Bentley fumbling and a refreshment break.
2. The basics: it unbolted the normal Audi way for rears. (Note to self--gotta find a thin 17mm wrench like a bike axle cone wrench for holding those caliper pins...) Because of the electronic brake, the time spent running down Bentley was easily made up by avoiding the old having to crank the brake piston back into the caliper like a C4 or 5 or a D2, and of course no climbing under the car to re-tension the parking brake cable like in the old days. All you need to do is use a standard brake caliper piston retractor and push it straight in. Of course what you can't do is clamp it from behind where the delicate parking brake motor gets in the way. Forget the C clamp like I use on many a brake set up; out came the (generic) piston crank-in set I use for Audi's now, but here it just gets pressure applied with no twisting. Really easy.
Pads have no wear sensors, but as I'll cover below, it is calculated by the car separately. Thus, easy again, no wires to undo.
A new one for me compared to other recent Audis--the rotor comes out with no need to remove the carrier bracket. Thus, loosen the set screw, whack the disk a few times with a soft mallet and off it comes. Thus, really easy to do rotors too if it's time for that.
3. Now the not so good sides of what I found:
a. The pad wear was really uneven as between the inside and the outside pads, and the much heavier wear was on the inside pad where you CANNOT see it much at all without the wheel completely off. That was true on both sides of the car, so I would say it is a design problem, not just some single caliper fluke or faulty factory installation. New pads are 10mm thick in the rear. The outside ones were 6 ½ and 7 mm, while in inner ones were about 4mm. That is a BIG percentage spread, and until I saw this I had actually figured the rear pads still had a lot of life by periodic inspections through the wheels seeing the outer pads. Wrong. Here is a picture of the four pads I pulled out. If you look carefully, the difference in thickness is pretty evident. The two thinner ones were on the inside.
<img src="http://pictureposter.audiworld.com/26081/img_4045crop.jpg">
Picture 2
If you look at the numbers, the inners were wearing at almost twice the rate as the outers. That's not good. Of course both the piston and the parking brake operate from the inside which would start to explain it. But, that shouldn't happen. Needless to say, I carefully greased the floating caliper pins as well as the pad contact points with the spring clips. Disappointing the much greater wear is on the hidden pad.
When I went to reset the pad wear in VAGCOM, it told me the car thought the rears were down to 3mm. So the one better news item here is somehow it decided the wear was a bit worse than the thinnest pad. How it got there I'm not sure since you would think it would look at the parking brake total travel over time, which would involve an average of both inner and outer pad wear. Quick math says using the most worn pad, it would get to metal by 47,500 total miles. Assuming the pads started at 10mm and it calculates linearly, the car would conclude it got to metal just past 40,000 miles
b. As I pulled the pads out, one of the vibration dampeners just fell off the pad on the left side. They are supposed to be riveted or spot welded on, so this was a failure. It's obvious in this picture:
<img src="http://pictureposter.audiworld.com/26081/img_4036crop.jpg">
Picture 3
This may explain finally why I had a bit of chatter on a slow stop the first time or so in the morning as the brakes got a bit of heat. In the details of Picture 3 you can see some letters and a number at the bottom of the pad on the left, starting with "FER". Thus I'm guessing the OEM supplier is Ferrodo, which I have come across on some prior Audis. The EBC's I replaced them with had a stick on anti vibration pad that locks into some distinct dimples in the pad backing.
c. Finally, the rotors. Okay, it's a W12 so it is somewhat heavier and gets up and goes and then stops maybe a step or two more lively than a 4.2 in everyday use. But the rotors are also sized up over the 4.2. Bigger (335mm) than the front rotors on my C5 4.2 even, which itself has strong brakes! The caliper unit is basically the same as the D3 4.2 I think, and the overall rear set up is quite similar to the C5 RS6. So, what's all this mean for the rotor? The new rotor spec is 22mm per (erroneous) Bentley, but both the new and old rotor (the old one at the outer edge) spec at 23.2mm (.915"). The wear limit nets to 20mm (.787") per the rotor stamping ). Bentley says 2 mm off of what they think is a 22mm rotor that also gets to 20mm. Well, I mic'ed the rotors I pulled off--which were in good condition. Min on one was .857", while on the other it was .854". Variance anywhere on the rotor was .003" or less, and visually the wear looks quite even and clean. You can see some of the rotor in the background of Picture 3 just above. Thus, rotor wear to date at 28,500 miles is .061" or 1.5 mm. That yields a life expectancy of about 2.1 of my current odometer reading, or about 60,000 miles. That does not agree with my prior Audi experience, which is basically I don't need to change rear rotors except for a brake job at over 100K miles or if they get quite scored somehow. Seems more like the minimum life of a front rotor driven somewhat hard to me, assuming it doesn't warp. Of course if the rotor had started at 22mm the math would be a lot different--it would run 5x my current mileage, but I can tell from the inner and outer lips it plainly started thicker than that.
Net--note to self and the board--these things wear rear rotors and pads a lot more than I would have thought. I figured the basic upsizing of the brakes took care of the added power and weight to net the wear about the same. Brakes perform great in the field, but the OEM pad situation and wear isn't up to what I would have expected.
4. New set up: EBC red pads, a careful home paint job with high temp brake paint from a rattle can, and the drilled and slotted OEM spec rotors (about the only aftermarket ones available besides straight OEM).
a. EBC Reds are ceramics, number DP31470C, aka standard brake pad code D1018. Box says they are for (C5) RS6's and Phaetons. Backing shape is identical to the OEM pads. They have a center slot cut in the pad, maybe for outgassing. The outer edge of the pad is the same width as the OEMs, but the inner edge nearest the hub tapers down quite a bit more. Swept area would be the same, but it looks like somewhat less pad material actually than the OEM set is touching the pad toward the inner part of the rotor. A picture of old vs. new rotors and pads:
<img src="http://pictureposter.audiworld.com/26081/img_4037crop.jpg">
Picture 4
b. Paint was spray on VHT brake caliper enamel in cast aluminum and black. I sprayed the calipers on the car with some basic tape masking and without undoing the brake lines. I had sprayed them with brake cleaner with some rag and brush work, and touched up the seam marks with a flat file. Oh yeah, truth be known I Dremeled out the VW logo on the caliper, leaving just the four rings logo cast into the metal (see the blank area above the four rings in Picture 6), plus the TRW markings to the left. The calipers dried overnight and I gave them one quick sanding between coats, just on the most visible areas. I removed the caliper brackets from the car, flat filed and Dremeled the obvious seams visible from the wheel side, especially the forward face where I put the decal. I masked all the bare metal areas (this and sanding were the longest steps; about an hour each), and gave them several coats before oven curing them, then sanded them and repainted. Drying time basically took off and on for a day+. Decal is from Xenonmods with a clear coat on top. From test experience the VHT clearcoat turns yellow at higher temps, so I went with a red decal instead of silver (that would end up gold if it yellowed), and I applied the clearcoat after I bolted the bracket back up, choosing not to go to the 350 degree oven cook. Last time I turned a front brake part with clearcoat yellow at about 400 degrees over about an hour. The silver paint and black paint hold up perfectly at those temps and even up to a sustained 450-500 degrees in the oven, and when baked get nice and hard.
c. The brake rotors are the supposed Disc Italia rotors from Brakeworld, which are really just machined OEM rotors (complete with laser engraved Audi part number). Goes with the fronts I did previously--the link to the front install is in my auto sig below. I'm catching up with E/CovertW12 who already has done the same in back.
This one shows the laser engraving on the OEM rotor, plus the 20MM H&R DRA spacer I use in the rear; I tweaked the image in Photoshop to bring out the markings and edges better; in real life the calipers look much smoother and the cooling fins look normal OEM rather than rough as they do here.
<img src="http://pictureposter.audiworld.com/26081/img_4048crop.jpg">
Picture 5
Another angle (pre-spacer):
<img src="http://pictureposter.audiworld.com/26081/img_4047crop.jpg">
Picture 6
Another angle all back together:
<img src="http://pictureposter.audiworld.com/26081/img_4050crop.jpg">
Picture 7
End result:
<img src="http://pictureposter.audiworld.com/26081/img_4053crop.jpg">
Picture 1
1. Degree of difficulty: To the post last week about the >$1,000 rear brake job by a dealer, all I can say now is that is really absurd! It was very easy to do. Among the easiest of any car I have seen in the rear. The hardest part by far was simply finding the right part of Bentley to execute the VAG COM command to release the brakes. If I did it without the paint on the new set up, I would say once the wheels are off it would take one hour with experience and decent tools, no more than two hours even with VAG COM and Bentley fumbling and a refreshment break.
2. The basics: it unbolted the normal Audi way for rears. (Note to self--gotta find a thin 17mm wrench like a bike axle cone wrench for holding those caliper pins...) Because of the electronic brake, the time spent running down Bentley was easily made up by avoiding the old having to crank the brake piston back into the caliper like a C4 or 5 or a D2, and of course no climbing under the car to re-tension the parking brake cable like in the old days. All you need to do is use a standard brake caliper piston retractor and push it straight in. Of course what you can't do is clamp it from behind where the delicate parking brake motor gets in the way. Forget the C clamp like I use on many a brake set up; out came the (generic) piston crank-in set I use for Audi's now, but here it just gets pressure applied with no twisting. Really easy.
Pads have no wear sensors, but as I'll cover below, it is calculated by the car separately. Thus, easy again, no wires to undo.
A new one for me compared to other recent Audis--the rotor comes out with no need to remove the carrier bracket. Thus, loosen the set screw, whack the disk a few times with a soft mallet and off it comes. Thus, really easy to do rotors too if it's time for that.
3. Now the not so good sides of what I found:
a. The pad wear was really uneven as between the inside and the outside pads, and the much heavier wear was on the inside pad where you CANNOT see it much at all without the wheel completely off. That was true on both sides of the car, so I would say it is a design problem, not just some single caliper fluke or faulty factory installation. New pads are 10mm thick in the rear. The outside ones were 6 ½ and 7 mm, while in inner ones were about 4mm. That is a BIG percentage spread, and until I saw this I had actually figured the rear pads still had a lot of life by periodic inspections through the wheels seeing the outer pads. Wrong. Here is a picture of the four pads I pulled out. If you look carefully, the difference in thickness is pretty evident. The two thinner ones were on the inside.
<img src="http://pictureposter.audiworld.com/26081/img_4045crop.jpg">
Picture 2
If you look at the numbers, the inners were wearing at almost twice the rate as the outers. That's not good. Of course both the piston and the parking brake operate from the inside which would start to explain it. But, that shouldn't happen. Needless to say, I carefully greased the floating caliper pins as well as the pad contact points with the spring clips. Disappointing the much greater wear is on the hidden pad.
When I went to reset the pad wear in VAGCOM, it told me the car thought the rears were down to 3mm. So the one better news item here is somehow it decided the wear was a bit worse than the thinnest pad. How it got there I'm not sure since you would think it would look at the parking brake total travel over time, which would involve an average of both inner and outer pad wear. Quick math says using the most worn pad, it would get to metal by 47,500 total miles. Assuming the pads started at 10mm and it calculates linearly, the car would conclude it got to metal just past 40,000 miles
b. As I pulled the pads out, one of the vibration dampeners just fell off the pad on the left side. They are supposed to be riveted or spot welded on, so this was a failure. It's obvious in this picture:
<img src="http://pictureposter.audiworld.com/26081/img_4036crop.jpg">
Picture 3
This may explain finally why I had a bit of chatter on a slow stop the first time or so in the morning as the brakes got a bit of heat. In the details of Picture 3 you can see some letters and a number at the bottom of the pad on the left, starting with "FER". Thus I'm guessing the OEM supplier is Ferrodo, which I have come across on some prior Audis. The EBC's I replaced them with had a stick on anti vibration pad that locks into some distinct dimples in the pad backing.
c. Finally, the rotors. Okay, it's a W12 so it is somewhat heavier and gets up and goes and then stops maybe a step or two more lively than a 4.2 in everyday use. But the rotors are also sized up over the 4.2. Bigger (335mm) than the front rotors on my C5 4.2 even, which itself has strong brakes! The caliper unit is basically the same as the D3 4.2 I think, and the overall rear set up is quite similar to the C5 RS6. So, what's all this mean for the rotor? The new rotor spec is 22mm per (erroneous) Bentley, but both the new and old rotor (the old one at the outer edge) spec at 23.2mm (.915"). The wear limit nets to 20mm (.787") per the rotor stamping ). Bentley says 2 mm off of what they think is a 22mm rotor that also gets to 20mm. Well, I mic'ed the rotors I pulled off--which were in good condition. Min on one was .857", while on the other it was .854". Variance anywhere on the rotor was .003" or less, and visually the wear looks quite even and clean. You can see some of the rotor in the background of Picture 3 just above. Thus, rotor wear to date at 28,500 miles is .061" or 1.5 mm. That yields a life expectancy of about 2.1 of my current odometer reading, or about 60,000 miles. That does not agree with my prior Audi experience, which is basically I don't need to change rear rotors except for a brake job at over 100K miles or if they get quite scored somehow. Seems more like the minimum life of a front rotor driven somewhat hard to me, assuming it doesn't warp. Of course if the rotor had started at 22mm the math would be a lot different--it would run 5x my current mileage, but I can tell from the inner and outer lips it plainly started thicker than that.
Net--note to self and the board--these things wear rear rotors and pads a lot more than I would have thought. I figured the basic upsizing of the brakes took care of the added power and weight to net the wear about the same. Brakes perform great in the field, but the OEM pad situation and wear isn't up to what I would have expected.
4. New set up: EBC red pads, a careful home paint job with high temp brake paint from a rattle can, and the drilled and slotted OEM spec rotors (about the only aftermarket ones available besides straight OEM).
a. EBC Reds are ceramics, number DP31470C, aka standard brake pad code D1018. Box says they are for (C5) RS6's and Phaetons. Backing shape is identical to the OEM pads. They have a center slot cut in the pad, maybe for outgassing. The outer edge of the pad is the same width as the OEMs, but the inner edge nearest the hub tapers down quite a bit more. Swept area would be the same, but it looks like somewhat less pad material actually than the OEM set is touching the pad toward the inner part of the rotor. A picture of old vs. new rotors and pads:
<img src="http://pictureposter.audiworld.com/26081/img_4037crop.jpg">
Picture 4
b. Paint was spray on VHT brake caliper enamel in cast aluminum and black. I sprayed the calipers on the car with some basic tape masking and without undoing the brake lines. I had sprayed them with brake cleaner with some rag and brush work, and touched up the seam marks with a flat file. Oh yeah, truth be known I Dremeled out the VW logo on the caliper, leaving just the four rings logo cast into the metal (see the blank area above the four rings in Picture 6), plus the TRW markings to the left. The calipers dried overnight and I gave them one quick sanding between coats, just on the most visible areas. I removed the caliper brackets from the car, flat filed and Dremeled the obvious seams visible from the wheel side, especially the forward face where I put the decal. I masked all the bare metal areas (this and sanding were the longest steps; about an hour each), and gave them several coats before oven curing them, then sanded them and repainted. Drying time basically took off and on for a day+. Decal is from Xenonmods with a clear coat on top. From test experience the VHT clearcoat turns yellow at higher temps, so I went with a red decal instead of silver (that would end up gold if it yellowed), and I applied the clearcoat after I bolted the bracket back up, choosing not to go to the 350 degree oven cook. Last time I turned a front brake part with clearcoat yellow at about 400 degrees over about an hour. The silver paint and black paint hold up perfectly at those temps and even up to a sustained 450-500 degrees in the oven, and when baked get nice and hard.
c. The brake rotors are the supposed Disc Italia rotors from Brakeworld, which are really just machined OEM rotors (complete with laser engraved Audi part number). Goes with the fronts I did previously--the link to the front install is in my auto sig below. I'm catching up with E/CovertW12 who already has done the same in back.
This one shows the laser engraving on the OEM rotor, plus the 20MM H&R DRA spacer I use in the rear; I tweaked the image in Photoshop to bring out the markings and edges better; in real life the calipers look much smoother and the cooling fins look normal OEM rather than rough as they do here.
<img src="http://pictureposter.audiworld.com/26081/img_4048crop.jpg">
Picture 5
Another angle (pre-spacer):
<img src="http://pictureposter.audiworld.com/26081/img_4047crop.jpg">
Picture 6
Another angle all back together:
<img src="http://pictureposter.audiworld.com/26081/img_4050crop.jpg">
Picture 7
The following users liked this post:
faisalfaisal (07-09-2023)
09-15-2008, 06:13 AM
#3
AudiWorld Super User
You need to start a D3 FAQ
If you look at my sig file, it has been done before for other models....I did it for the D2, things that are not on audipages.
Nice write up as usual!
Nice write up as usual!
09-15-2008, 06:50 AM
#4
AudiWorld Super User
Thread Starter
So far I'm parking mine in my auto sig, but you are onto something.
Stoney's C5 index is another great example (and labor of love).
09-15-2008, 06:54 AM
#5
AudiWorld Super User
Thread Starter
Wheels are the optional old style RS4 OEMs in 20's...
Thanks. If you followed various prior posts, these are the ones Wheels America did on the job training with I guess over 3 or 4 attempts. Ended up with that beatiful quasi mirror finish outside. But not a great job on the inner barrel if you look at the pics there--I cleaned them before bolting them back on.
Trending Topics
09-15-2008, 06:53 PM
#8
AudiWorld Member
Very impressive. A few questions.
I think you nailed the look with the silver/black and subtle audi rings. I thought the S8 logo upfront was nice, but the rings take it IMHO. Are you considering changing the fronts?
Questions: I may found a solution to the high dusting pads but would like to try them before i advise anyone otherwise. What is neccessary via vag-com and the process to do the rears? Does one need the vag-com system?
Questions: I may found a solution to the high dusting pads but would like to try them before i advise anyone otherwise. What is neccessary via vag-com and the process to do the rears? Does one need the vag-com system?
09-15-2008, 06:57 PM
#9
AudiWorld Member
Also, what the specs on the spacers? Front and Rear - Thx
I think this something i would like to do to push the wheels out to the corners a bit more...
09-15-2008, 07:45 PM
#10
AudiWorld Super User
Thread Starter
VAG COM answer; fronts
You need the VAG COM cable of course with the downloaded software they provide to anyone. Thus you either need to buy one, borrow one, or get someone to help. It is basically five steps, two steps up front and three afterward:
1. Preliminary: clear any codes in the parking brake module.
2. Issue the command for the parking brake motor to open up, going for the option of planning to put in new pads instead of reinstalling old ones--a few keystrokes all per Bentley.
[Do pad replace]
3. Issue command to close parking brake motor
4. Tell the brake unit by adaptation the pads are 10mm thick
5. Issue command to recalibrate rear brakes in general (same as the noise it makes once in a while in everyday use).
Takes about 5 minutes on front end, 5 or 10 minutes max on back end.
Fronts: I have done them already if you look at the link to write up in my autosig. But yes, I still plan to go to a better paint job than the brush on first gen. Of all things, I later bought a complete set of calipers for a W12 for $100 off ebay, so I tore them down for painting. I have the bodies and brackets all painted up the same silver and black and oven cured. Still debating decals. Can't find a W12 decal; if I did I might repaint the S8 trim gray again (like it is) and then use a W12 decal. Also vaguely played with trying to get the decal guy to do a logo with the sport red logo parallelagram and a W12 superimposed on it instead of S8. I played with the straight A8/W12 pad retainer trim too, but it still looks basic--that's where I yellowed the clearcoat tested under high heat.
1. Preliminary: clear any codes in the parking brake module.
2. Issue the command for the parking brake motor to open up, going for the option of planning to put in new pads instead of reinstalling old ones--a few keystrokes all per Bentley.
[Do pad replace]
3. Issue command to close parking brake motor
4. Tell the brake unit by adaptation the pads are 10mm thick
5. Issue command to recalibrate rear brakes in general (same as the noise it makes once in a while in everyday use).
Takes about 5 minutes on front end, 5 or 10 minutes max on back end.
Fronts: I have done them already if you look at the link to write up in my autosig. But yes, I still plan to go to a better paint job than the brush on first gen. Of all things, I later bought a complete set of calipers for a W12 for $100 off ebay, so I tore them down for painting. I have the bodies and brackets all painted up the same silver and black and oven cured. Still debating decals. Can't find a W12 decal; if I did I might repaint the S8 trim gray again (like it is) and then use a W12 decal. Also vaguely played with trying to get the decal guy to do a logo with the sport red logo parallelagram and a W12 superimposed on it instead of S8. I played with the straight A8/W12 pad retainer trim too, but it still looks basic--that's where I yellowed the clearcoat tested under high heat.