Over the past few decades, electrification has resulted in the virtual elimination of several once-key automotive liquids. Power steering fluid is the most obvious example across the board, but electric vehicles have also dispatched with engine oil, automatic transmission fluid, and of course, gasoline. However, innovators in the industry aren’t done yet. Two suppliers have already developed solutions for eliminating another common maintenance fluid: brake fluid.
While there are already cars available with brake-by-wire pedals that actuate the brake master cylinder electronically, Brembo’s Sensify and ZF’s EMB take things one step further and feature electrically actuated calipers rather than hydraulically actuated ones. In the case of the former, all four calipers can be specified to feature an electromechanical mechanism that clamps the pads to the discs, while in the case of the latter, all four calipers or only the rear calipers can be electromechanical, with the second setup controlling each hydraulic front caliper by way of a separate electronically actuated master cylinder. Contrast this with a traditional brake caliper setup in which all caliper pistons are acted upon hydraulically, and it’s clear we’re soon to be playing in a whole other realm.
So what benefits do electromechanical brakes have in the real world? Well, they promise faster actuation than hydraulic brake solenoids, which should lead to more precise control of each individual wheel. Automatic adjustments can be made at the calipers themselves for weight transfer and differences in surface friction, and threshold braking in seriously slippery conditions can be achieved by computer algorithms rather than by driver skill. Also, since the pedal is entirely electronic, there’s no heavy traditional pulsating anti-lock braking feedback that may scare drivers not used to getting into ABS during panic braking instances. In addition, electromechanical calipers promise to eliminate brake pad drag which should reduce particulate emissions, and they should integrate seamlessly with regenerative braking in electrified vehicles.
There are purported perks for automatic emergency braking, too. ZF claims that its electromechanical calipers can offer a 29.5 feet reduction in automatic emergency braking stopping distance from 62 mph over a standard hydraulic braking system. That could be the difference between changing your shorts and filing a claim, but without further details on how that number was reached, we’ll have to wait on third-party validation.
Oh, and there are some potential maintenance benefits to this evolution of brake-by-wire. Because electric calipers keep the pads clear of the discs in regular operation, it’s possible that pad changes could be a cinch. There might not be a need to retract the pistons if retraction is their default state to avoid dragging the pads on the discs. Also, removing the need for traditional brake lines eliminates the possibility of having, say, a rear brake line rot out after 20 years in the rust belt. It also means that brake fluid flushes on electromechanical calipers literally can’t be neglected (because there’s no brake fluid to flush).
Are there any potential downsides? Well, I could see a few. The first is unsprung weight, as adding a powerful electric motor and mechanism to a caliper is almost certainly a heavier proposition than a few ounces of flexible brake tubing and brake fluid. The second is packaging, because oh brother, these calipers look huge. Sure, they mean manufacturers won’t have to run brake lines, but the sheer depth of the calipers may require compromises in knuckle design and suspension arm placement to achieve sufficient steering angle. I also can’t help but wonder about rats. They don’t normally chew metal brake lines, but wiring? Happens all the time.
Still, so long as rodents don’t find themselves attracted to the cabling, electromechanical brake calipers offer up some interesting possibilities. With contracts already inked as per Automotive News, expect to see these systems appearing in production cars within the next few years.
Top graphic images: ZF
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What about work-hardening of the copper wires leading to wire breakage?
Right? My washing machine keeps breaking its motor wires from the constant movement the drum makes but that just leads to dirty clothes and a 20 minute fix.. not soiled pants and a hospital visit.
Plus the brake wires would be exposed to corrosive salt spray.
Pretty sure they’re insulated….
Salt…. finds a way.
Um, yeah, no.
I hope they fail closed because every modern vehicle seems to have electrical gremlins and I’m not sold on being killed by rich teenagers because their brand new BMW crossover shorted and blew a fuse and now it has no brakes.
How much does one of those calipers with 2 honking actuators hanging off of it weigh? Seems like a huge steaming heap of unsprung mass… I’d also have questions about thermal performance and minimum wheel sizes.
Factory wheel sizes are crazy so this would probably push GM to put 36 in rims on everything.
At least we’ll always have blinker fluid, no matter how advanced/AI/annoying cars evolve to become. So there’s that vital automotive fluid at least.
I think you’re mistaken. Blinker fluid is used to lubricate the muffler bearings.
I also use it to start the burning on my charcoal grill.
Brakes are vital to your car’s safety and one failure could mean a pretty dramatic death. That’s why you should trust your braking needs to experts at Lucas Electronics.
More real world safety liability relying on less than stellar electrical system reliability and programming done exclusively by morons with potentially major consequences for failure and reduction in operational feel for largely theoretical gains in performance. The only people threshold braking are people who very likely don’t want this. For the normals, that’s what ABS is for and that already extant BS braking assist (there to make up for the common problem of people not actuating the pedal hard enough in an emergency, which this wouldn’t do better other than maybe better reaction time). Hydraulic brakes are remarkably low maintenance and cheap, but I’m sure electric garbage calipers subjected to high heat will be more reliable and cheap to replace or repair than hydraulic, especially with the prevalence of electrical issues. Some companies can’t even make a damn connector that can withstand basic engine compartment heat and I’m to trust it on brakes?
I, for one, look forward to the spectacular and frustrating ways that brands, like Stellantis or JLR, will inevitably fail.
I also look forward to the repair bills for the German versions of these vehicles that’ll, I’m sure, will require a unique, and new, triple-square-derived tool to remove.
Oh please. If one of your BMW’s rear calipers fail it’s just going to be a routine engine drop to fix it, for reasons…
OK smarty-pants, just what all electric solutions can replace blinker fluid?
In case anyone is wondering, the car in ZF’s photo is a BYD Han
Glad this answer is here so I didn’t have to figure it out to satiate my own curiosity.
Honestly with how well the one pedal driving works in my 25 Leaf I’m open to getting rid of hydraulic brakes.
1 liter of hydraulic fluid can poison 1 million liters of water.
One pedal worked fine on the GT350, but I’m a advocate of the giant brakes it had.
That must’ve been a GT350H.
Engine braking worked great with super high compression and the axle grease it used for oil. Really annoying going from 1mph to 40mph to 1mph w 0 brake use.
Poison? How so? Brake fluid isn’t especially harmful stuff. Obviously not advocating dumping it in a stream, but the LD50 on the stuff in DOT3 requires pretty huge doses.
For a RWD or AWD EV, I could see just having some sort of emergency/parking brake integrated into the rear drive module, and delete the rear wheel brakes entirely for vehicles that are just driven normally and not something like a sports car that includes track driving in its design. I’d still want some sort of conventional front brakes though, for the occasional times of regen reduced or disabled due to 100% charge or subzero F temps, panic stops and such, but I’d also like to have those be zero maintenance for the life of the vehicle. Over 100k miles on the bolt, and the brakes still look new.
I mean VW moved to drums on their BEVs and it’s not hard to add a mechanical cable and a e-brake lever.
I’m all for R&D on these, but we need to be very, very sure of their failure modes before putting them on all 4 wheels.
29.5ft at 62 mph is 1/3 of a second. That sounds reasonable to claim as time savings from electronic over hydraulic brake reaction time.
Engineer here,
People always like to point to airplanes as an excuse to do fly-by-wire stuff. What they dont consider is that airplanes make Landcruisers look like unreliable turds. The engineered lifespan, REQUIRED service intervals, and redundancy to make these as reliable as they would be on airplanes would make them entirely unaffordable on cars.
IF we can treat them like planes and ground cars that havent been serviced, then I’d be all for it. Unfortunately, that wont happen.
Now we will get cars with no brake feel to go along with the no-feel electric steering.
On a side note. If you haven’t tried out your ABS, find a quiet stretch of road, check carefully behind you and hit the picks as hard as you can. No feel and hear what happens, hunt around on your dashboard for your spectacles and dentures and drive off knowing you will not be surprised if you need to brake really hard in an emergency.
If you have never needed to emergency brake, are you really “driving”? /s
It’s all fun and games till the caliper vomits out a pad and the ebrake doesn’t work because the balance bar just pulls the empty side.
Have you ever driven a Prius? Some cars have that shit perfectly figured out. I cannot for the life of me tell where the regen stops and the friction brakes begin.
And this a 2012 car! I’m sure the gen 2’s are dialed-in, too.
I can’t say that I have driven a Prius. I’m just extremely skeptical of what “enhancements” electric brake actuation will bring.
It may be wonderful.
Totally fair. My point is only that some aspects of it have been around for a while now.
BMW has already eliminated brake feel, so nothing more would be lost.
The older I get, the more convinced I am that I don’t actually want anything in my cars that can be fixed by an over-the-air update.
Radio, but then again I want to be bug free enough to not need it.
Radio? Why would a radio need an OTA update?
To renew your subscription of course.
Still not following you. Why would you need a subscription to radio? Sat radio I suppose. But how that works barely rises to the level of update. More like a text message.
The joke was about how modern manufacturers want you to pay subscriptions for things you already have. Using access to the radio in a car as the punchline.
Ah! Now I get it.
Because it’s the only thing I can think of being better having a Ota, then I said it better not need it.
First thing that comes to my mind is will the elimination of a direct connection from foot to caliper via fluid cause a similar lack of feel that happened when going from hydraulic to electric steering?
You can bet on it. Mercedes did brake-by-wire for a while and feel was *terrible*. So was the reliability to the point they have put a 25yr unlimited miles extended warranty on that system. Though that said, electric steering is not inherently bad, at least when one is talking about electric *assistance*, and not actual steer-by-wire. Nobody complains about the electric steering in Porsches, Miatas, and GTIs, and those have had it for years. But the steer-by-wire in Nissans was *horrible*.
I would prefer to have brakes that don’t NEED a 25 year extended warranty. And while I am about the least paranoid person on the planet, do you REALLY want your brakes to be something hackers can potentially mess with, given you can be damned sure that any car with this system is going to be well and truly connected to the mothership?
Biggest benefit of EPS as assist is that it’s failsafe. Done right, you should be able to pull the fuse and have an unboosted rack that’s much easier to handle than if you were fighting a dead hydraulic pump.
If you drain the fluid (or it’s failed because it all leaked out), you aren’t fighting the pump. BTDT. The steering geometry of a car with power steer will still make it suck to steer. And having to spin an electric motor won’t help at all.
I mean, we already lost some of that feel with the move from cable to hydraulic
Not really. Cables are stretchy, far more so than incompressible fluids are.
Have you actually ever driven a car with cable brakes? I have, and you don’t want to. Hydraulic is a quantum leap over cables in the same way the car was a quantum leap over the horse.
Yes, yes I have
Then you weren’t paying attention.
Agreed. Cable actuated brakes are still common on bicycles but hydraulic disc brakes are slowly taking over. Cable actuated brakes feel much worse since both cable and cable housing stretch and compress when the brakes are applied.
Great example!
I think we are heading for a Cubano Notre of sorts with people trying to keep cars the road as long as possible and the gubmint trying to get them off the road.
Of course, people resisted them new-fangled hydraulic brakes over mechanical brakes (I want a direct connection to the brake shoes, dangit, not some mythical “fluid” connection) when they were voting for Silent Cal and we’ve had them for darn near 100 years now!
What is a “Cubano Notre?” Google surmised it might be a sandwich.
Probably a misspelling of Cuba Norte, North Cuba, tying into the idea of people going to great lengths to keep old cars running because they can’t (Cuba) or supposedly don’t want to (US) buy new vehicles that are “worse”.
Henry Ford had to be convinced- pretty hard- to put hydraulic brakes on the 1929 Model A.
The Model A didn’t have hydraulic brakes, Ford stuck with cable brakes through the 1938 model year
Damn, History Channel lied to me.
I’m not really sure how these are claiming all the supposed benefits, a modern hydraulic eboost is a pretty capable piece of hardware. I’d also think you would want to move the vehicle to a 48v architecture rather than a 12v to keep the amperage requirements semi reasonable for these.
I think comparing it to a “standard brake system”, which I take to mean ye olde pure hydraulic with no computerized assistance is doing a lot of heavy lifting here.
I can assure anyone that if my Mercedes thinks there is an imminent collision and that I am not braking hard enough, it will yank the pedal out from under my foot and plant faces into the windshield all by itself even with good old hydraulic brakes. That system definitely can prevent accidents, BTDT when some idiot cut me off. The car nailed be brakes before I could, the magic of automated emergency braking.
I can’t help but think this is yet another thing that has advantages to the automaker, but very limited advantages to the owner along with plenty of potential for wallet-busting events down the road. Of course if you only lease new cars for three years at a time it’s probably amazing.
MY next car most certainly will do none of these things. The chances of my ever buying another new car rounds to zero. Too many cars that I actually like out there in low mileage cream puff condition.
I remember when they told us that mechanical valve operation (camshafts, pushrods, rocker arms, etc) would be replaced by solenoid-operated valves. Since I can’t afford a Koenigsegg, I’m still waiting.
Cool, 12v battery goes out, no brakes.
Back up power? I have had my hydraulic brakes fail before from weird non-reproducible master cylinder problems.
Sure, there’s room for a couple of “D” cells in each caliper.
I’ve had my engine quit and have no brakes and no steering for that matter, it was an LM002, but 6000lb automobiles are not exactly uncommon nowadays.
With how well the one pedal braking works on my Leaf I’m surprisingly open to electric brakes, that being said I’d prefer air brakes that fail on vs fail off like all hydraulic brakes.
I’m actually thinking these need to be configured like the air brakes on a semi – when NOT powered, their default condition is fully engaged.
The big trucks do this with springs (to engage the brake pads) and air pressure (to counteract the springs, when the truck is powered up and moving). When there’s no air pressure, the springs force the brakes on and thus you have a “everything must be working or else you’re stopping” failsafe situation.
They need something along these lines (though maybe not air) for these too.
Yea! One less puddle on the driveway.
I’m wondering if there’s some sort of power failure redundancy like a big ass capacitor or something that would allow breaking to still happen if something happened to the rest of the electrical system? I’m sure there’s something from the Aircraft industry that would be able to answer that situation.
This is my question too.
Maybe make them so their fail state is on, like semi-trailer brakes, and the electric action releases them. That still has downsides, but would be better than crashing into something.
I mean you could have a thermal battery, basically it generates electricity via molten salt, and the electricity that goes into it is just to heat it, so if your 12v were to fail you’d run off the thermal battery.
I think there may be other concerns about hauling around a molten salt battery in an automobile. Plus how much energy are we talking about has to be dumped in to it to keep it in a molten state, since cars are not always running?
I mean the Think City electric car had a molten salt battery. You can also build molten salt batteries to be suddenly heated up in an emergency via methods other than electric resistive heating.
A conversion kit for older cars would be a welcome safety addition.
So true, great idea, it would be so much easier to run wires than custom bend brake lines and to get rid of one channel drum brakes on old cars would be much safer.
This should be treated like ABS was at first.
Put the electric only brakes on the rear wheels, but keep the front hydraulic.
Time will be needed to see if the transition to all 4 being hydraulic makes sense and is proven to be safe.
Agreed. Hydraulic systems aren’t perfect, but electrical gremlins have that name for a reason.
I have seen hydraulic Gremlins before, but they are pretty rare.
Don’t feed Gizmo after midnight. And keep him away from the pool!