Just call me extremely skeptical as .2 sec is a relative eternity. If my brakes took nearly that long between press and actuation, I would feel it and immediately take it in for service. This also assumes that the Brembo times were zero.
It's good to be skeptical.
This does not assume the Brembo times to be zero. It is based on observing the change in the velocity graphs of cars with stock brakes and that same car, same driver, same track, same day with StopTech brakes. The shape of the velocity vs time curve is different at the transition from not braking at all to the linear range. To get an accurate measurement of the improvement in reaction time requires a telemetry device with a switch connected to the brake pedal, a bunch of accelerometers and changes to the software on the laptop connected to the radar gun. So stuff has to be purchased, software has to be written, and techniques have to be baselined. All of this will take some time and money.
The improvement is visible graphically. To get a hard and fast number will require the new test set-up. And the improvement will obviously vary from car to car. An STi with factory Brembos (or 350Z Track Model) may show zero reaction time improvement and a Ford Taurus may show an enourmous improvement.
An additional benefit of the new test fixture is the ability to prove (or disprove) the theory that stainless braided teflon lines also improve reaction time and thus shorten braking distance in a panic stop. If they do, then one might also assume the bronze calliper bushings from www.bimmerword.com and www.turnermotorsport.com will have similar impact. I'm impatiently waiting to find out.
If you think 0.2 seconds is an eternity, then how long do you think it takes from when the driver turns the steering wheel to X degrees that the car stabilizes in the new direction?
2001 540i 6-Speed
StopTech 4-wheel big brake upgrade (ST-60 front/ST22 rear)
M5 3.15 Limited Slip Differential M5 Front Swaybar
Dinan Stage 3 Suspension
Dinan Front Strut Tower Brace
Rogue Octane Short Shifter & Transmission Mounts
European Dash Conversion CDV Deleted (of course!)
Bluetooth, NAV-TV, DVD Player
2006 Chrysler 300C SRT8 w/StopTech ST-60 front/ST-40 rear BBK 2007 Corvette Z51 Coupe 6-Speed w/StopTech Trophy ST-60 front/ST-40 rear 2009 Honda Fit Sport w/NAV w/Acura Integra front calipers, StopTech floating rotors on order
If you think 0.2 seconds is an eternity, then how long do you think it takes from when the driver turns the steering wheel to X degrees that the car stabilizes in the new direction?
Hehe, that will depend on the shocks, springs, tires, sway bars, ....
I would not be surprised to see a number close to 1s for a stock M car.
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The clutch pedal is a throwback to the days of carburation and OHV engines. It has served us well but its time to let go and embrace the future.
I assumed the zero Brembo times for simplification purposes. Any amount above that must be added to the stock brake response time to get the .2 sec difference.
Changing the direction of a car and then stabilizing the suspension thereafter is a completely different subject and has to do with both the steering system and the suspension, particularly the latter.
Hehe, that will depend on the shocks, springs, tires, sway bars, ....
I would not be surprised to see a number close to 1s for a stock M car.
Close! Very good. But try doubling that number. I was in a class on Friday that covered suspension dynamics and one of the sections illustrated that topic. More than one of us was skeptical. (There's that word again!) The steps involved were broken down for us and then illustrated for us with a CarSim video, using a "real" car. I think it was a VW Golf GTi in this example.
Last edited by DZeckhausen; 1st April 2005 at 02:27.
The issue here is how the brake system works. Based on a lot of heresay so far we have evaluations ranging all over the map about the effectiveness of the M5 brakes. Why are we debating how many angels can dance on the head of a pin when we haven't seen the subject of the debate.
I'm sure that the brakes could be improved. Does anyone here think that no one with a porsche ever upgrades their brakes? I'd guess that the whole discussion would go away if the factory had put nice red brembos inside the wheels.
As I would assume Dave would aggree, the whole system must be upgraded to get the better braking he describes, from brake lines to proper calipers, pads, preload of the pads when the throttle snaps shut, and perhaps even different disks. I said different since I wouldn't assume larger is the right answer.
Lastly, Infinity had an option on the G35 coupe of Brembos as part of the sport package. Funny, but the stock brakes stopped in the same distance! Were they there for cosmetics and customer appeal? or for real improvement? Hmmm...
Should BMW charge more for brakes that only a few of us would appreciate? Then what would be diddle with on our cars? Oh, and as much as I love my M5, it's not an exotic.
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JesseM
[b]2006 M5 Sapphire Black,Indi red, HUD, rear bags, fold seats, comfort access, BBS RG-Rs,275/35 -285/35, Dinan front & rear roll control 56K Miles, still getting 1200 miles per liter TWS
2003 Silver 325XiT
2003 Black Infiniti G35 Coupe
2005 BMW K12S(<8min N'ring)
Vintage Triumph m/c's(110 rwhp/liter -w/pushrods)
...preload of the pads when the throttle snaps shut...
That seems like a really clever idea. I'll have to ask my contact at Delphi if this is a strategy being considered (or already implemented) to improve reaction time in conjunction with "brake assist." At the class on Friday, we discussed the sensors used to measure brake pedal position and differentiate between a normal hard stop and a panic stop. The position vs time charts were radically different, which explains why most people helped by "brake assist" are never aware that it happened. If you could do something similar by observing a related unique characteristic to the way the gas pedal is released prior to a panic stop, you could start to apply brake pressure to remove compiance from the system in preperation for a panic stop even before the driver touches the brake pedal. The kicker will be if there is a high false alarm rate.
Did you think this up yourself or did you read somewhere that this is actually being done or in the works? Either way, thanks for mentioning it!
The issue here is how the brake system works. Based on a lot of heresay so far we have evaluations ranging all over the map about the effectiveness of the M5 brakes. Why are we debating how many angels can dance on the head of a pin when we haven't seen the subject of the debate.
I'm sure that the brakes could be improved. Does anyone here think that no one with a porsche ever upgrades their brakes? I'd guess that the whole discussion would go away if the factory had put nice red brembos inside the wheels.
As I would assume Dave would aggree, the whole system must be upgraded to get the better braking he describes, from brake lines to proper calipers, pads, preload of the pads when the throttle snaps shut, and perhaps even different disks. I said different since I wouldn't assume larger is the right answer.
Lastly, Infinity had an option on the G35 coupe of Brembos as part of the sport package. Funny, but the stock brakes stopped in the same distance! Were they there for cosmetics and customer appeal? or for real improvement? Hmmm...
Should BMW charge more for brakes that only a few of us would appreciate? Then what would be diddle with on our cars? Oh, and as much as I love my M5, it's not an exotic.
Interesting comment and very similar to many here already. Must remember this when seeing discussion next time about the relative merits of M cars and AMG's. The fact that people here don't seem to have a rudimentry understanding of brakes and their limitations, demonstrates that many M drivers are just boulavard cruisers, who would probably be better off in an AMG, for the usage their cars get.
At the class on Friday, we discussed the sensors used to measure brake pedal position and differentiate between a normal hard stop and a panic stop. The position vs time charts were radically different, which explains why most people helped by "brake assist" are never aware that it happened. If you could do something similar by observing a related unique characteristic to the way the gas pedal is released prior to a panic stop, you could start to apply brake pressure to remove compiance from the system in preperation for a panic stop even before the driver touches the brake pedal. The kicker will be if there is a high false alarm rate.
Recently on the freeway in my MB S class with the whole pre safe thingy, I had to brake suddenly and hard for about two seconds for an idiot driver swapping out of a much slower moving lane near an offramp. The car decided that there was an emergency situation and continued braking for another 2 seconds AFTER I had already removed my foot from the brake pedal entirely. (it also starts closing sunroom, moving seats more upright etc in preparation for a potential impact)
Recently on the freeway in my MB S class with the whole pre safe thingy, I had to brake suddenly and hard for about two seconds for an idiot driver swapping out of a much slower moving lane near an offramp. The car decided that there was an emergency situation and continued braking for another 2 seconds AFTER I had already removed my foot from the brake pedal entirely. (it also starts closing sunroom, moving seats more upright etc in preparation for a potential impact)
The Delphi systems don't continue braking after the driver lifts his foot off the brake pedal. But it does continue at full force if the driver lifts partially. It's characteristic of drivers in panic stops to initially spike the brake pedal and then lift off when they should stay on it full. The reduction in stopping distance in a panic stop with brake assist is amazing.
In your case, it clearly did more than you wanted it to. I wonder if Mercedes is much more agressive than other manufacturers with this system. Curious what would have happened in the Corvette C6 in the same situation.
The car decided that there was an emergency situation and continued braking for another 2 seconds AFTER I had already removed my foot from the brake pedal entirely. (it also starts closing sunroom, moving seats more upright etc in preparation for a potential impact)
I developped the Brake Assistant of the E46.
I dont know the system of the S-class, but that afterbraking effect is a problem is a common problem.
Mostly you have afterbraking for about 100ms, but the river feels it as a second.
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