S8 brakes
07-13-2001, 07:50 PM
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S8 brakes
<img src="http://pictureposter.audiworld.com/17157/AlconTA6_a.jpg">
<img src="http://pictureposter.audiworld.com/17157/alcon_rotor.jpg">
<img src="http://pictureposter.audiworld.com/17157/alconta6_c.jpg">
<img src="http://pictureposter.audiworld.com/17157/alconta6_d.jpg">
<img src="http://pictureposter.audiworld.com/17157/s8_hre_9.jpg">
1st priority - brakes ... Done
Some may recall my earlier post grumbling about the S8 brakes. These were undoubtedly an improvement over those on an A8; but from 70 mph, I'd never been able to activate the ABS system on clean dry asphalt roads, even on a moderately steep downhill gradient. The Dunlop SP8000's had more stopping power than the brakes, which is not the way it's supposed to be. IMHO, the original brakes also had excess pedal travel.
The problem's been solved with these new front brakes:
Alcon TA6 calipers - six pistons (titanium nitrided SS), ceramic/aluminum alloy monobloc
Alcon Rotors - slotted 14" x 1.25", 48 vane with aluminum hat
Brake fade is history, and pedal feel has noticeably improved. Though slightly larger in diameter than the original 13.6" rotor, the Alcon rotor and aluminum hat is almost 10 lb lighter per corner! Caliper weight is about the same. My only complaint is that the rear brakes now look seriously inferior by comparison, though performance at the rear is actually fine. Perhaps I could upgrade rear to a two piece rotor for the weight savings only.
What else can I say? Overkill? Almost certainly, but I'm extremely pleased.
BTW, Vortrag supplied the brake kit.
<img src="http://pictureposter.audiworld.com/17157/alcon_rotor.jpg">
<img src="http://pictureposter.audiworld.com/17157/alconta6_c.jpg">
<img src="http://pictureposter.audiworld.com/17157/alconta6_d.jpg">
<img src="http://pictureposter.audiworld.com/17157/s8_hre_9.jpg">
1st priority - brakes ... Done
Some may recall my earlier post grumbling about the S8 brakes. These were undoubtedly an improvement over those on an A8; but from 70 mph, I'd never been able to activate the ABS system on clean dry asphalt roads, even on a moderately steep downhill gradient. The Dunlop SP8000's had more stopping power than the brakes, which is not the way it's supposed to be. IMHO, the original brakes also had excess pedal travel.
The problem's been solved with these new front brakes:
Alcon TA6 calipers - six pistons (titanium nitrided SS), ceramic/aluminum alloy monobloc
Alcon Rotors - slotted 14" x 1.25", 48 vane with aluminum hat
Brake fade is history, and pedal feel has noticeably improved. Though slightly larger in diameter than the original 13.6" rotor, the Alcon rotor and aluminum hat is almost 10 lb lighter per corner! Caliper weight is about the same. My only complaint is that the rear brakes now look seriously inferior by comparison, though performance at the rear is actually fine. Perhaps I could upgrade rear to a two piece rotor for the weight savings only.
What else can I say? Overkill? Almost certainly, but I'm extremely pleased.
BTW, Vortrag supplied the brake kit.
07-14-2001, 05:41 AM
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Unsprung weight
John,
I'm sorry to say I don't notice any difference at all!
By the time I realized there was such a weight difference, it was too late to do a seat-of-the-pants back-to-back comparison. On top of that - even though I run with 38 psi up front on the street, I never thought the S8 had a harsh ride, so I never really paid much attention to it. With 10 lbs less unsprung weight, the improvement I do expect is in tire adhesion. Unfortunately, that's much harder to measure, especially since the gains will only occur on rougher roads, but every little incremental bit helps. And now you've got me wondering what the total unsprung weight is for a front corner. Wheel, tire, brakes, upright, CV joint, wheel bearing, and 1/2 of suspension elements and halfshaft: it's probably 100+ lb.
In addition, of course, this is also rotating weight. With less energy being dumped into this "flywheel", less horsepower is wasted, and acceleration times should also improve (very slightly). I have computer software that predicts 5.58 sec for the 0-60 mph time of an S8. When I reduce total vehicle weight by 20 lb, and front wheel/tire weight by 10 lb each, the predicted 0-60 time drops 0.05 sec to 5.53 sec ... not much, but I'll take it. The S8 motor is wonderful; but I would have liked to been above the 400 hp psychological barrier, and anyway, there really is no such thing as too much power.
Randy
I'm sorry to say I don't notice any difference at all!
By the time I realized there was such a weight difference, it was too late to do a seat-of-the-pants back-to-back comparison. On top of that - even though I run with 38 psi up front on the street, I never thought the S8 had a harsh ride, so I never really paid much attention to it. With 10 lbs less unsprung weight, the improvement I do expect is in tire adhesion. Unfortunately, that's much harder to measure, especially since the gains will only occur on rougher roads, but every little incremental bit helps. And now you've got me wondering what the total unsprung weight is for a front corner. Wheel, tire, brakes, upright, CV joint, wheel bearing, and 1/2 of suspension elements and halfshaft: it's probably 100+ lb.
In addition, of course, this is also rotating weight. With less energy being dumped into this "flywheel", less horsepower is wasted, and acceleration times should also improve (very slightly). I have computer software that predicts 5.58 sec for the 0-60 mph time of an S8. When I reduce total vehicle weight by 20 lb, and front wheel/tire weight by 10 lb each, the predicted 0-60 time drops 0.05 sec to 5.53 sec ... not much, but I'll take it. The S8 motor is wonderful; but I would have liked to been above the 400 hp psychological barrier, and anyway, there really is no such thing as too much power.
Randy
07-14-2001, 05:54 PM
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I'm sold, questions...
I have a "measly" 2000 A8L and not an S8, however I noticed a similar lack of ability of the stock brake system with my summer wheels and tires -- BBS-RC 18" with pilot sports 245/45/18. I noted the same problem with my APR chipped 2000 S4 and pilot sports 235/35/18's.
What is the availability and installation for a brake upgrade like that? A8 stuff is pretty sparse comared with the S4 stuff. I can't even find someone who has an A8 chip w/ spare ECU -- not like the 34 different chips for the S4!
I am in Central MA, USA ... I'll bet April might chime in with a recomendation...please do!
What is the availability and installation for a brake upgrade like that? A8 stuff is pretty sparse comared with the S4 stuff. I can't even find someone who has an A8 chip w/ spare ECU -- not like the 34 different chips for the S4!
I am in Central MA, USA ... I'll bet April might chime in with a recomendation...please do!
07-14-2001, 09:57 PM
#6
wheel weight and software?
I weighed the S8 wheel with a Dunlop 8000 tire and it turned out to be 56 LBS. I've also installed a lighter battery (-29 LBS), removed the front sub mats (-12 LBS), and I'm looking to install a compact spare for a 30 pound weight savings. I'm having no luck finding a compact spare. What software are you using to do the predictive modeling?
07-15-2001, 05:58 AM
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Availability/Installation
Chris,
I can sympathize; but as bad as it is finding performance add-ons for an A8L (a measly car??), try finding stuff for an S8. These Alcon's are probably the first brake upgrade on any S8 in the U.S. Whoever wanted to provide an upgrade, they first had to get their hands on an S8 to get the dimensions needed for the caliper mounting bracket and rotor hat, and it's not the same as an A8. At least for A8 brakes, though, you do have good choices available from Alcon, Brembo, and probably others. The A8's been around long enough that those selling kits have already done their homework.
As I noted in the original post, my Alcon's are from Vortrag, located near Detroit. I live in Pennsylvania, but happened to be near Detroit and was able to bring my car in to have everything installed. I'm glad I did, there were minor adjustments needed. Having seen the installation done once, though, I could do it myself in probably about 4 hours. The toughest part may just be getting the old rotor off. Having said that, though, there are some awfully large forces and high temperatures involved during braking, and it's important to do the install correctly if you expect to be able to stop the car, every time. Also, of course, it's a significant investment in your car that you'll want to get right the first time.
So to get back to your questions:
Availability - An Alcon setup like mine for an A8 should be readily available from Vortrag at the link below. Call and ask for Todd Candey.
Installation (assuming you're not doing this yourself) - I have experience with two Audi dealers; one would do the installation, and the other .. probably not. Also, someone visiting this site should have recommendation for an installer in Central Mass. [Suggestions April?]
One caveat: The S8 originally came with F40 Brembo's, and these were what I didn't like. There are brakes, and then there are BRAKES. Brembo does make a much better brake than the production F40 used on the S8. The same applies to Alcon, you can do better or worse than my TA6 setup. I recommend going for the best you can afford or rationalize. Other useful links listed below.
http://www.alcon.co.uk/
http://www.apracing.com/
http://www.brembo.com/
http://www.stoptech.com/
Good luck,
Randy<ul><li><a href="http://www.vortrag.com/">http://www.vortrag.com/</a</li></ul>
I can sympathize; but as bad as it is finding performance add-ons for an A8L (a measly car??), try finding stuff for an S8. These Alcon's are probably the first brake upgrade on any S8 in the U.S. Whoever wanted to provide an upgrade, they first had to get their hands on an S8 to get the dimensions needed for the caliper mounting bracket and rotor hat, and it's not the same as an A8. At least for A8 brakes, though, you do have good choices available from Alcon, Brembo, and probably others. The A8's been around long enough that those selling kits have already done their homework.
As I noted in the original post, my Alcon's are from Vortrag, located near Detroit. I live in Pennsylvania, but happened to be near Detroit and was able to bring my car in to have everything installed. I'm glad I did, there were minor adjustments needed. Having seen the installation done once, though, I could do it myself in probably about 4 hours. The toughest part may just be getting the old rotor off. Having said that, though, there are some awfully large forces and high temperatures involved during braking, and it's important to do the install correctly if you expect to be able to stop the car, every time. Also, of course, it's a significant investment in your car that you'll want to get right the first time.
So to get back to your questions:
Availability - An Alcon setup like mine for an A8 should be readily available from Vortrag at the link below. Call and ask for Todd Candey.
Installation (assuming you're not doing this yourself) - I have experience with two Audi dealers; one would do the installation, and the other .. probably not. Also, someone visiting this site should have recommendation for an installer in Central Mass. [Suggestions April?]
One caveat: The S8 originally came with F40 Brembo's, and these were what I didn't like. There are brakes, and then there are BRAKES. Brembo does make a much better brake than the production F40 used on the S8. The same applies to Alcon, you can do better or worse than my TA6 setup. I recommend going for the best you can afford or rationalize. Other useful links listed below.
http://www.alcon.co.uk/
http://www.apracing.com/
http://www.brembo.com/
http://www.stoptech.com/
Good luck,
Randy<ul><li><a href="http://www.vortrag.com/">http://www.vortrag.com/</a</li></ul>
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07-15-2001, 06:42 AM
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Re: wheel weight and software
John,
The simulation was done with "Drag Racing Pro" from Performance Trends. I've used this primarily for checking the gear selections for our SCCA Club Racing Formula Continental. They also have very good motor and suspension simulation software. I've used their "Engine Analyzer Pro" extensively to test modifications to the Ford 2L motor in our FC. It's an impressive piece of software; but unfortunately, it can only simulate up to 4 valve heads, not the 5 valve head of the S8.
And you're ahead of me when it comes to putting the S8 on a diet. I've also looked at that massive battery, and it was on my list. Avus/SP8000 at 56 lb, no wonder changing a tire is work. BTW, have you noticed that 9-1/2 ft of bare pipe that's used as a heat exchanger for the power steering fluid? It's hung as far forward and as high as possible in front of the A/C condenser, and I plan to replace it with a small Setrab type heat exchanger located lower and about 2-3 ft further back. Let us know of any other weight saving you find, perhaps at some point we'll be able to post a list that can shed 500 lb from the car. At least for the track, you've already found 97 lb! The weight loss will obviously improve acceleration, but I'm really more interested in handling improvements.
Randy<ul><li><a href="http://www.performancetrends.com/">http://www.performancetrends.com/</a</li></ul>
The simulation was done with "Drag Racing Pro" from Performance Trends. I've used this primarily for checking the gear selections for our SCCA Club Racing Formula Continental. They also have very good motor and suspension simulation software. I've used their "Engine Analyzer Pro" extensively to test modifications to the Ford 2L motor in our FC. It's an impressive piece of software; but unfortunately, it can only simulate up to 4 valve heads, not the 5 valve head of the S8.
And you're ahead of me when it comes to putting the S8 on a diet. I've also looked at that massive battery, and it was on my list. Avus/SP8000 at 56 lb, no wonder changing a tire is work. BTW, have you noticed that 9-1/2 ft of bare pipe that's used as a heat exchanger for the power steering fluid? It's hung as far forward and as high as possible in front of the A/C condenser, and I plan to replace it with a small Setrab type heat exchanger located lower and about 2-3 ft further back. Let us know of any other weight saving you find, perhaps at some point we'll be able to post a list that can shed 500 lb from the car. At least for the track, you've already found 97 lb! The weight loss will obviously improve acceleration, but I'm really more interested in handling improvements.
Randy<ul><li><a href="http://www.performancetrends.com/">http://www.performancetrends.com/</a</li></ul>
07-15-2001, 12:52 PM
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Re: icsamerica - compact spare (space saver)..........
I know the Lotus Esprit has a large space saver, I seem to think it is an 18" tyre. I can check if you want - as I work at Lotus.
Let me know.
Andy P.
Let me know.
Andy P.