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Brake by wire

21K views 29 replies 16 participants last post by  ViscontiVerde 164L* 
#1 ·
After a year of owning the Stelvio and not really knowing what "brake by wire" actually meant, I found two sites for information. One is Popular Mechanics that uses the Alfa as their example and one by Brembo highlighting a little more of the whys and wherefores. It's all about electric cars and autonomous driving.


I checked the links and they work.

Uses Alfa Romeo as theirexample of what’s to come
https://www.popularmechanics.com/cars/car-technology/a22126727/brake-by-wire/


Brembo Brakes By Wire System - How It Works
 
#5 ·
Wish these guys would go into the practical application of the tech. They do a great job describing the function but how that relates to the actual day to day use of the system is ehh…


For instance do any of you realize the system responds like you, basically meaning if you activate the brakes slowly, with barely enough pressure to move the pedal, the brakes will respond slowly with a mushy pedal that goes almost to the floor and has vague response because the system is applying the type of force that you are.


Push the pedal quickly and with strong pressure and the brakes respond the same way, with a quick response and a firmer pedal.


Normal brakes will deliver the same feel regardless of how you push the pedal.


IMO the reason Alfa's are not the shortest stopping vehicles in magazine testing has to do with the tests themselves. It is not an emergency, it is some one driving down a straight course till they reach a pre-determined spot, then they hit the brakes in a practiced manner and see how the car stops. In most cars that works to give a baseline. Not in a car with brake-by-wire though, since the system will respond faster when the driver brakes faster...in a real panic situation, especially with bad traction thrown in (wet road or dirt), an Alfa will stop much faster than it's competitors. Trying to get a buddy with a Grand Cherokee to let me record a direct comparison between it and the Stelvio, he doesn't want to. Because it is embarrassing. We have played around off road and his car cannot turn, brake, or accelerate anywhere near to what the Stelvio does. Not even close, 60-0 braking at the drylakebed was about 200 feet further in his car, it also took him almost another 100 feet just to hit 60. In terms of turning, it was just funny....not a competition.


So, he told another friend who has an Audi Q5. He thought that could take me off my high horse. Didn't happen. In anyway you want to compare, braking, acceleration, turning, once you put them on dirt the Stelvio simply runs away laughing. It doesn't walk, it runs...not close. Buddy with the Audi still doesn't want to talk to me about it, actually left mad when we got together to compare the vehicles, and won't give me the footage from his camera for me to use on a video! His cost almost $8000 more with all the options and could not keep up. He is also mad that after a day of driving hard on dirt he has interior rattles now, and had to go to a shop to get some of the underbody panels reattached. My car is like basically like the day I drove it home.
 
#7 ·
Because of how the feedback is calibrated.


The system is not perfect, and how it communicates what is happening to the driver is the biggest weakness for sure.


IMO that is the untapped modification....someone needs to figure out how to reprogram the feedback for the braking system. Theoretically it should be possible to go in through the OBD system and "hack" the brake feedback to be firmer and higher. Basically like "chipping" the brakes. Probably more complex than just that, but....it is software, code can always be rewritten.


Figure out how to change the brake feedback/responsiveness through the brake controller and have a new modification with no competition in the marketplace.....BMW is getting the same system, Mercedes has a similar one already. More manufactures will adopt too, be first to market in a new category of tuning......tune brake feel directly, with no parts, just software. Whoever figures that out first will print money.
 
#8 ·
I always wondered if changing the brake pads to something with more initial bite would help ease the transition. A pad similar to the Ferodo 2500's. More braking at the beginning of the pedal travel. I like to get on the bakes lightly to settle the car before I brake hard. For me that's my biggest complaint about the car. I think it is the weak link and what I would like to change first.
 
#9 ·
Be interesting to try. I *think* you would feel absolutely nothing at the pedal. Not saying the pads won';t perform a little better, just think the system will not translate that into "feel".

Truth is, I just started doing stuff and assumed the brakes would respond correctly regardless of the feel (basically video games brakes). They did, and now after adjusting what I look for in terms of feel (I expect it to be subtle compared to most cars) I really like the brakes and find they respond just like I want....they just don't really communicate what they are doing well. But they DO communicate better then the brakes on my video game rig, which is actually their closest relative...
 
#13 · (Edited)
basically,you just have standard hydraulic brakes without ABS, just requires a bit more foot pressure. From document:

Master Cylinder
The brake pedal is directly connected to the master cylinder.
The master cylinder is designed to reach pressures higher
than the traditional applications with power brakes because,
in the event of system failure, the driver must be able to stop
the vehicle acting on the brake pedal without exerting
excessive force.
The master cylinder consist of a cylinder, two pistons, an Oring seal and a sensor actuated by the position of the pedal
stroke.
The sensor is of Contactless type: the position of a magnetic ring, joined to the primary piston, is read by an
electromagnetic transducer.
 
#15 · (Edited)
Took a while, but it's second nature now. We all need to recalibrate to new tech on occasion. Just like electric PS 10 yrs ago.


It is that consistent braking rate of speed reduction that takes a while to get used to. As you slow more, you need to apply more "pedal" if you want to slow quicker. Old hydraulics used to do this by nature of design. At first you find yourself slowing inadequately at the end of a braking cycle till you learn to add slightly more pressure as you decelerate. Now I love it. Would love to try at the track.
 
#17 ·
The Mercedes E55 AMG had BBW. Awesome car, hated the brakes. The Stelvio is a little better than the E55 but I still can't stand the delayed feedback and overly aggressive bite when it's not warranted. Steering feedback is lazer accurate, and then you have a computer braking for you. A chaperone on an Italian car??? WTF! Ferrari introduced the F1 transmissions because it shifts quicker than any human. Incredible feeling! Braking however, is not something a computer can do better than most drivers.

Gear heads are getting ripped off of a decent drivers car. The brakes are the biggest disappointment on the Alfa by far!
 
#18 ·
Under what circumstances you think the bite is too aggressive?


Not trying to be combative, genuinely interested in what you think. Personally I have not found that to be the case, but we have different experiences/expectations, so want to know what yours are.



...mainly cause I agree with you overall, so I want to know why you think what you think about the rest.


While the function is nice and I do think the computer can do some things better than a traditional brake set up...the pedal feel/feedback and much of the general tuning of the response could be improved significantly, and I hope Alfa figures this out and issues a software update since it would be fixable through that.
 
#19 ·
gee, depending on how 'natural" you want your brakes, sorry, I have to disagree - this IS something where the "computer" is accomplishing things no human can.

but I'm biased, because I go back to pre antilock, so know the difference. then the debate was anti-lock on the front or the rear. luckily with motorcycles, we didn't have to be in the debate, with separate controls for front and rear brakes the rider could modulate each wheel ...perfectly and instantly. maybe not quite.

unless you have two hand levers and two brake pedals, you CANNOT brake as well as this system - and even if you did you probably couldn't react as quickly anyway.

newer street motorcycles use abs, and I rather expect the reason it's not on motogp/fi is so the operator is actually responsible for something - they've got plenty of other electronic aids.
 
#20 ·
I must say that I like everything about the Stelvio drivetrain and drivability, and stop-a-bility - all super controllable.

The brakes have definitely saved me a time or two when I've encountered quick braking situations, and to me, they feel quite natural and easy to physically understand, and when your re-action is to stand on them, bam, you're stopped before you know it.

If braking by wire is good enough for F1 drivers, it's almost good enough for me. Not that I think I can drive like them, but because I can't!
 
#25 ·
The brakes in the Stelvio felt a little weird to me at first, but without realizing it I've gotten used to them and I'm able to brake just as smoothly now as I can in other cars. I've found it just requires much lighter pressure than most vehicles; like when coming up to a red light, just barely press the pedal instead of even pressing it 1/4 or 1/2 way (well, unless you NEED to stop quicker, then obviously press it as hard as you need to!).

Also, I think the "jerky" feeling that many people complain about it is more to do with the 3-2 and 2-1 downshifts rather than the brakes themselves. Whether in automatic or manual mode, those seem pretty pronounced (even more so in manual mode I find).

The more I drive it the more in sync I get with how it behaves and it's really a joy! And I haven't found that the difference in pedal feel in the Alfa has effected my smoothness in other vehicles, either. I do find that other vehicles have gotten a lot slower since I got the Alfa though!
 
#27 ·
Joy: We saw the most beautiful sunset and stormy sky tonight heading home on picturesque Lancaster County roads loving the drive at the same time. Life is about experiences and beauty. Stella provides a holistic esthetic experience for those with the sensitivity to appreciate these things.

We are a tightly differentiated group of drivers. Appliances and freeways for everyone else.
 
#28 ·
Joy: We saw the most beautiful sunset and stormy sky tonight heading home on picturesque Lancaster County roads loving the drive at the same time. Life is about experiences and beauty. Stella provides a holistic esthetic experience for those with the sensitivity to appreciate these things.

We are a tightly differentiated group of drivers. Appliances and freeways for everyone else.
Just joined the group of Lancaster County Stelvio owners. It's a great experience!!
 
#30 ·
Delayed feedback??????
 
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