What does “brake by wire” mean in these new F1 cars and how does it affect the drivers?
Posted By: James Allen  |  05 Feb 2014   |  11:45 am GMT  |  202 comments

Felipe Massa’s quote at the weekend about the new ‘brake-by-wire’ systems on the 2014 F1 cars taking some getting used to has sparked a lot of discussion on the JA on F1 site, with readers wanting to know more about what it is and how it works.

Let’s start with an explanation from the Sauber F1 team, “The braking system concept is totally new, taking the form of a brake-by-wire system for the first time at the rear wheels. This has become necessary due to the significantly increased performance of the ERS, which requires much greater variations in rear wheel braking torque than previously. With brake-by-wire, an electronic system measures how hard the driver presses the brake pedal and then – using the additional information from energy recuperation – determines in a split-second the amount of braking pressure that should be fed through to the rear brake callipers.”

In other words, because the ERS (Energy Recovery System) is so much more powerful on these new cars compared to the KERS on the 2013 cars, harvesting energy when the car is braking – 161bhp of energy compared to 80bhp with the KERS – it is essential that the engineers install a system to compensate for the powerful effect that has on brake balance and braking stability. This makes it acceptable for the driver and doesn’t destabilise the car with a sudden balance shift. A lot of the lap time in modern F1 comes from stable braking.

Massa’s quote was: “The brakes work in a different way. It’s electronic brakes, brake-by-wire, and I still need to improve the way I’m braking because it’s different. It’s a little bit strange sometimes,” he said.

So, how does it work?

An F1 car has two brake systems for safety – front and rear – so that if one fails the other will stop the car. For 2014, the rear brake system has the brake-by-wire, which assesses how much brake pressure the driver has called for when he presses the pedal and an electronic system modulates the power to the rear brakes, allowing for the ERS effect, that is taking energy to charge up the kinetic motor generator unit (known as MGU-K). It smooths out the process, slowing the car in a consistent way at the same time as ensuring the maximum energy harvest for the ERS.

Ideally, the driver would feel nothing unusual with this system, in that it should provide consistent, stable braking on demand. The job of the new rear brakes system is to ensure consistency. Some people might argue that the electronic assistance to the driver makes it a “driver aid” and in the sense that without it, it would be difficult to maintain a brake system that the drivers would be happy with. This damps it out. But as it’s written into the regulations it doesn’t fall foul of the regulation saying that the driver must drive “alone and unaided” – a rule that prevents the use of traction control, ABS and countless other technical goodies.

Here is the exact wording of the new technical regulation on brake by wire.

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Really thrilled to know about the working of the brake wire. Good and good information.


If this new system is stop rear wheel lock up..What happens in those situations where a driver needs to lock up all 4 wheels to wipe off speed ie before collisions etc., won’t this new system remove that.and increase impact speed/force


Hi James, someone mentioned earlier about turning the car using the brakes. Did you find out any further?

Also, one of the critical settings for modern F1 cars has been engine braking or more specifically how much engine over run was used to offset the engine braking effect (or off throttle blowing of diffusers for e.g). How do the new systems incorporate this effect? As they used to consume fuel (by supplying a throttle %)do the new systems consume electrical power to prevent the rear wheels locking?

Having the right engine brake setting is critical for stable braking and off throttle/coast balance, especially in faster corners like Maggots/Becketts where the rear wheels dragging slightly can help keep the nose tucked in.


“This makes it acceptable for the driver and doesn’t destabilise the car with a sudden balance shift. A lot of the lap time in modern F1 comes from stable braking.”

Rather sad. In the old days, a lot of passing was really one driver being able to brake better than another. A great driver was the one who had that intelligent foot, who could modulate that brake pedal. With the advent of carbon brake rotors and lithium, then beryllium calipers, braking has become less about smart feet, and more about the ability to mash the pedal at the very last second possible.

I’d rather they keep mechanical hydraulic braking.


In the hope of being of some help to you I will explain.

When I submit the post can be seen on the page ok, if I go off the site on returning to the site and to that page the post is gone, if I post again that disappeared post will pop-up more often than not but not always.


OK will pass that on


And ditto exactly like last time as soon as I press submit that missing post pops-up again.

Are you reading JAMES?


Yes we are reading. Checking it out

Funny thing is no-one else is reporting that


The rear brake calliper will be much smaller this year.

The drivers will have to adapt to the feel of the new system (brake feel).


Does this mean maintains rear brake temps will be harder since there less demand from them? Not sure if some asked this already.


As this year the cars will be much more traction limited as a result of the new power unite a much bigger effort will be made to gain some advantage in this aria (traction out of corners) more so when power output/outright speed/flat-out racing have all been limited by the fuel flow and fuel weight for a race as mandated by the rules.

The state of play will be totally different this year, one of the most important things this year and without which a driver has very little chance not only of not winning a race but even that of finishing a race is radio contact between car and pits.


That RBR was mimicking traction control out of corners last year was talked about a lot, the cat was out of the bag in Canada when tyre marks were observed as the car exited the corners plus the strange noise from the engine, it was clear that they were using the MGU-K in harvesting mode at part throttle, but this doesn’t mean they were breaking any rules because while harvesting is supposed to take place under braking nothing prevented them of using the brake pedal on exiting a corner and under throttle, no matter how light.


James, this topic is so interesting. Can the MGU-K be used under acceleration to maximize traction coming out of the corner? Similarly also to maintain balance at full cornering? This area seems so ripe for fiddling.





6th 2014 at 2.35 pm, James Allen reply. “What are you referring to” –Mod.

Another post to this page having gone missing, right here today.


No offence intended but some real incredible comments on here about F1 racing matters by some that follows F1.

“The car must only have four wheels mounted externally of the bodywork, with only the front two steered and only the back two driven”.

No energy is released TO or harvested from (on) the front axle as the front wheels are not connected to the power source of the car.


And when the ERS boost is used the ERS (MGU-K) is augmenting X-power to that of the IC engine, Harvesting is done only when the brakes are used.


Is it defined by the rules to install ERS generator on the rear axle only?

and the reason? most of kinetic energy releases on the front axle..


The regulations as are stipulate (two rear driven wheels), also an ERS MGU-K that can augment X-power to that produced by the IC engine, all this to the driven wheels, also stipulates that this MGU-K can harvest X-power back to the ES/batteries, for that reason the MGU-K is geared to the front of the IC engine crankshaft.

The more a wheel is loaded the more the braking effort (force) that can be applied before said wheel will lock-up, so the more aero down-force the more braking effort (force) that can be used.

Because of the MGU-K harvesting which adds a great level of engine braking to that of the IC engine it is at the rear wheels were the most braking effort (force) changes are taking place and ditto the most difficult to control now beyond the capability of the front/rear brake balance (bias) adjuster as used by the driver.


The braking system with this electronic design will be exploited by Being able to deliver extremely light braking forces to just the rear wheels. This will allow more consistent power delivery, reducing wheel spin by essentially acting as a clutch. With rear bias set on the brakes, drivers will essentially be using the first 2-3 cm of braking pressure purely as traction control on the gear shifts. They won’t need nearly as much overall breaking power during the races anyway as there will be lots of lift and coast rather than late braking. For fuel saving. Alongside engines, those with the best braking system will be in with a real advantage this year. I think Ferrari looked to already have something like this in place which would explain the smoother torque


“Does the system only harvest power from the wheels that are driven when the ERS boost is used?”

Please think about that a bit more – or have you invented the impossible perpetual motion engine?

You cannot add power in order to take it back out at the same time! They call them Motor Generator Units for a reason… they can either consume energy (taking electrical power from the batteries) or generate power (charging the batteries) it is one or the other – there is no way it can do both at the same time!


There is also the other dynamic which is sending additional power from the MGU H to the MGU K directly

Engineers say that there is a lot in that


That’s the interesting bit, and the bit that’s relevant to road cars. You could do away with the storage element (i.e. the heavy batteries) and still get more power and economy from having MGU-H directly powering a motor on the drive train.

I want a road car with that.


Why do the regs restrict the system to the rear? Regular cars expend about 70% of braking force through the front wheels. Maybe it’s less for high downforce cars but momentum will always push the weight of the car forwards.

Did they know it would reduce stability and control and therefore ban ERS to the front wheels? Is it on its way with the next regs?

Or is ERS a complete con- just converting un-used power going to the driven wheels to charge the system?

Does the system only harvest power from the wheels that are driven when the ERS boost is used?

Surely applying ERS to the rears only, makes it a token effort. If they are serious about efficiency, all wheels will be used and that will drag F1 into the realms of All Wheel Drive.


ABS is not allowed in F1 but than many a thing was not allowed but ways have been found by teams of how to circumnavigate the FIA wording that forbid driver aids, one such example was last year one a team was mimicking traction control out of a corner by the use of the MGU-K harvesting under part throttle.

The FIA can keep things under control to any which level they wish because they are able to access the ECU mapping.


Wonder how long this formula will last. All these regulation changes must cost millions.

If you’ld ask me, it would be good old V10 all the way again.


And add a little bit of data from the actuator on the steering rack and hey-presto, inside wheel braking as per the 2006 Macca

If the ERS not fixed and directly related to the pressure applied to the brake pedal then I don’t see how this is not a driver aid – Just stamp on the pedal and let the throttle position algorythmn work out where you are on the circuit, how far to the corner and therefore the best option for energy recovery and speed retardation.


Watching F1 races on national TV (as we don’t have any retired F1 driver) I saw many times “civilian” sport commentators mislead about who was the real leader of the moment as tire management necessities,rather than pilot ability /car performance dictated the pace in the remaining laps.

This year even experienced BBC commentators will watch in total suspense if the driver in front will not slow down or even stop before the finish line out of fuel.

As for the “Drivers must be “alone and unaided” yet :” of Craig (above), they already had power steering, throtle aid (at start) mnow they have brake “tutor”, maybe the day when F1 will be a 100% secure sport as driver will drive from the pit wall is not very far.

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