I did the math on the speeds in gears for the S4 in the C&D test and they yield only a 6500RPM redline. I think that the consensus was that it would be 6800RPMs. Anyone know for sure? I've noticed that C&D's & R&T's speeds in gears are often based on the wrong maximum engine speed.

If, C&D's # are accurate on braking, that is very bad. To pay that much to have for an S4 and the braking is that many feet.
I don't understand why they are not putting better brakes on than that.
70-0 in 169 feet? Those are not improved brakes IMO. Sheesh.
-C.

nt

Let me put it to you this way. I was doing closed track brake testing with my A4's big brake upgrade (Alcon B-Type 4 piston calipers w/ 13" Coleman rotors) on literally bald SP8000 tires and worn rear brakes. With repeated threshold (hot braking), my car was getting 70-0 in 65-68ft range.
I'm sure the new tires on the S4 are better than the crappy-worn SP8000s I had on for those tests. C&Ds braking tests show a stopping distance that is more than double. This leads me to think that the brakes on the S4 are essentially barely upgraded from the stock A4.
That, to me, is disappointing, as even I have thought seriously about getting the new S4.
-C.

I know they are 4 pistons but no amount of pistons will change law of physics - You can only apply so much force on the rotor before it locks up but if you move the force further away from center then you may be able to get a little closer to the pending lock-up point and be more effective. Your breaks are bigger, right? Also, arent bald tires better performers in dry conditions? Especially when they are hot.

Still 65-68 feet for 70 - 0 sound pretty unreal. Are you sure you don't mean 165-168? Perhaps the most significant digit is assumed and I misunderstood. If so, then the hot flat rubber and bigger breaks would explain the diff handily.

Yeah, but look at the rest of the cars in the test:

70-0 distances
S4 169
M3 167
C43 159
9-3 167

The S4 is not out of line with the rest of the pack and the max 10' difference could easily be because of tires. Your stopping distance is... uhhh, I'm speechless!

nt

.

Even the M3 took an extra 15 feet to stop compared to their previous test. It is all the tires. Look at old A4 (pre-sport package stopping distances) and compare them to A4's with the sport tires--there's about a ten foot difference in the braking distances.

BTW, 70-0 in 65 or 68 feet is physically impossible in a car that's not using jet thrust or something similar to stop. That's equivalent to around 3 G's of stopping power.

Very true... tires make a huge difference!

When I switched from the stock RS-As that came on my '97 to SP8Ks my (man, should I say it.... err ok, here goes... no flames please) G-Tech numbers dropped by 12 feet. Same road same everything except for tires.

According to my S4 brochure the redline is 7000rpm, but no one knows exactly 'how' much except Audi. Curves can be manipulated-what is need is an actual printout showing hp at wheels, then based on factual data one could estimate hp at the flywheel ( I'm sure Audi has this kind of info. in their engineering data bases).

witness it for yourself. Seriously, come to Michigan and I'll be glad to show you. We ran many, many runs, it wasn't a fluke and it is not impossible. The tests were accurate and yes, these stopping distances are amazing. The brake calipers are the same brakes that AudiSport uses on the touring cars, except that they have full dust and weather seals. The old addage "you get what you pay for" is really the truth. I'm braking at the brakes markers on the race track less than half of where I had to brake when my brakes were stock.
Sure, Audi couldn't probably put this level of brake on a production car, but I would expect at least at a minimum some bigger and better braking on a car with more power such as the S4. Sure, the competition may be in range, but just because they do it doesn't mean that Audi shouldn't up the ante for safety sake.
I guess I'm just thinking that for the money for the cars in that level, they should have better stopping distances.
-C.

No "1" in front of that number. 60-0 best was 57 feet. These were controlled field tests.
Yes, these brakes are far more than Audi is going to put on their production car. I've thought seriously about getting and S4 so I'm just thinking out lous here. I just kind of expect that if I'm going to pay about 45k, I want better braking than that. If I got one....now I'd have to upgrade brakes right away.
But hey, I know plenty of guys that have had to buy upgraded brakes for their BMW M3s for track events. So I guess it's not really different in that respect.
-C.

It's just that I'm thnking that for a couple thousand more (what the hell...it's already practically a house payment) it would be nice to add a decent upgrade brake option at time of order. We could even call it the "sport brake package" option. I guess all I'm saying is regardless of whether or not the other car mfgs. are doing about the same distances....it's not that great IMO.
Maybe I'm just thinking that most people that have these higher hp cars are going to be pushing beyond 70mph and possibly even going to track events. They're going to need very good brakes.
I know, I wouldn't do a track event (any more) on brakes with those stopping distances on a faster car. My car is not yet faster than a stock S4 and I can't imagine doing an event without the brakes I have with the power I have now.
-C.

Yep, 12" rotor, I have to question the 4 piston caliper until I actually see one in person though. Yes, I know, I've read the brochures, but everyone of the S4's I've seen so far still have the same caliper as the A4, but coupled with the A8 rotor. Kinda explains the stopping distance too.

As far as changing the laws of physics, you're right, can't do that...
However, certain calipers have the ability to generate much more clamping force with the right amount of modulation to allow that additonal clamping force to be evenly applied to delay the impending lockup of the rotor.
They're are also a few other things here that affect how soon the rotor locks up. Pad material, pad type, piston configuration in the caliper itself. Not even to mention how well the caliper is held in position (carriers, etc) during braking. These are all things that help to better apply whatever clamping force the caliper develops. Not changing the laws of physics, just putting them to good use...

Todd Candey
Vortrag Motorsports Inc.

I think bald tires on a track where there is probably little in the way of dirt/rocks/water etc. would perform much better than tires with treads as there would be a much bigger contact patch. I think your tires had a lot to do with the short braking distance.

I thought I heard the S4 had huge brakes up front?

If you defend yourself again, I will call you an absolute idiot and I know from your history here that you're not. This is the first time I've had to get like this since this forum started. Please check your numbers. According to R&T, a $1,000,000 Porsche 911 GT1 will do 60-0 in 98 feet and 80-0 in 154 feet; by extrapolation, 70-0 should be about 125 feet -- Still nearly double the number you claim.

There's much more to how a brake kit performs than just size alone. Obviously, they are not that efficient based on those 70-0 numbers.
BTW, the brake tests were performed on a very long flat straight away (about 2 miles in length) in a secured parking area. There were plenty of rock and debris and not the world's best pavement. Worn tires are not the same in performance to sticky track tires, either. When hot they lose grip. I know this for a fact because I had quite a lot of major sliding when those tires were hot on the racetrack, the weekend before this test.
-C.

nt

That rate of deceleration is similar to the level of acceleration top fuel dragsters create at the line (i.e. 0 to 60 in 1.29 seconds); that rate of acceleration/deceleration is simply not possible with a car that has the A4's wheelbase, weight, weight distribution and tire deformation characteristics (dragsters tires are inlfated to around 2-3 psi and deform during wheelspin). So long as the braking power of the brake is greater than the traction power of the tires, a stronger brake will not help a single tested stopping time. That 911 GT1 I quoted above would do the 60 to 0 stop in about 2.23 seconds, covering 98 feet in the meantime, and having an average deceleration of 1.23g. Doing the 70-0 stop in 68 feet would require an average 2.42g deceleration for the 1.32 second long period it would take to stop. I don't even think Formula 1 cars can get even close to that kind of stopping power at speeds under 70MPH where there is no aerodynamic downforce generated.

If you want to run the numbers you can solve the following two equations to come up with the values for "a", the acceleration rate in feet per second per second, and "t", the time:

a*(t^2)=s
a*t=v

"v", the velocity, would be the foot per second velocity going into the stop
"s", the distance, in feet, covered during the stopping/deceleration run
1 "G" is 32 feet per second per second

Whatever. I made the offer to prove it and you can still call me an idiot. I'll be at R.A. this fall, if Michigan is too far.
These tests were witnessed by a whole group of people, time and time again.
So you can call everyone idiots, but the facts are what they are. Obviously the only way to prove it to you is for you to see it yourself.
-C.

nt

Some basic info...
The 99 Corvette C5 with stock brakes stops from 60 in 115 ft.
With the Baer Racing/Alcon B-Type upgrade, it does it in 90ft.
The Baer Racing/Alcon B-Type upgrade on the Mustang Cobra allows that car to stop in 96ft.
The above tests done by Baer Racing.
The Motor Trend test of the Porsche 911 Twin Turbo, 1996, 60-0 stopping distance is 93 feet.
This is a stock car.
Funny thing here is that except for the porsche, all of the cars that anyone has posted here are all rear wheel drive...
It's not out of the question for the awd system to add a 30% improvement in braking...
Even the Porsche which posts the best stopping distance of all of the stock cars uses calipers that are good, not exceptional... We have actually put Alcon B-Types on the front and rear of a 911 turbo and the difference is truly amazing.
I won't bother quoting a distance on that one however, because I'm sure that I too would be an idiot.

It's not that production cars can't be made to stop in under 100 ft. from 60 mph (your setup is proof and I for one don't doubt it), it's just that no automaker is doing it (OK, maybe the 996 is an exception, but you know what I mean). Competition is everything: Until someone in the $40K sport sedan class ups the ante and shows real, measurable marketing and sales results from it, brakes will continue to be the weak link in ALL these vehicles. Hence, worth your upgrading.

I AM anxious to see tests of the new M5. Given it's overall performance envelope, we might get lucky on the brakes for this (admittedly, twice as expensive) super sport sedan....

-- David F.
1.8TqMS
E30 325is
And envying your MONSTER binders, Cathleen

Before I had to get off on this tangent, my point was only that I would expect at least a little better option available at that price point, regardless of manufacturer.
As I said earlier, I know it would not be strategically feasible for Audi to put the massive brakes I have on a production car, but I still think they should at least offer an upgrade option that significantly betters the stopping distances. Regardless of what the other competitors in the market are doing.
A better brake kit costs a few thousand more. People pay extra to have a sport package option and the quattro option. It would be much easier to have a brake upgrade option that can be financed in with your overall car payment and then have those parts included in your Audi Advantage warranty.
I'm thinking from a safety perspective that the power capabilities of these cars keeps increasing yet the braking is not that good by comparison, IMO .
Anyone who has been on the track knows that after a few events they realize that stock brakes just don't cut it.
Anyone who drives an S4 or M3 is not usually going to be a mild-mannered driver. I just think that the manufacturers should offer better options...perhaps something in between the performance of my upgrade and what the stock brakes offer. It wouldn't be that expensive IMO.
-C.