RE: BMW M8 confirmed with new adjustable brake tech

[mwstewart]

RacerMike said:

Not entirely true in this case. IPB/Brake By Wire isn't really taking any control away from the driver, and it's introduction isn't to do so. It's primary drivers are a reduction in weight (good) and complexity (good), and improvement in performance (needed to deliver some of the safety features needed by incoming legislation) and cost.

Before worrying too much, I'd recommend having a go. Honestly, it feels like a big step on from the semi by wire systems currently around, and it highlights as well that no brake system for the last 30 years has really had any actual brake feel. I'd argue that you don't actually get any 'brake' feel with any servo assisted pedal as the force variation is way too small to make it through the assistance. My Caterham race car arguably did have the potential to feel when a wheel was about to lock, but I can't honestly say if that was entirely through the pedal. It was probably a combination of everything.

I did say to facilitate, however the development of these systems is entirely due to control (or lack of it). I would argue that overall system complexity is higher but the packaging is smaller.

With the exception of the throttle plate, I don't think there is a better driver control interface than a physical one, but my measure of performance is interaction and feel rather than safety and cost. I take the (simple) view that brakes and steering are basic systems that were perfected many years ago, and the advances we have seen, and continue to see today, are driven by requirements other than those that will reasonably increase my enjoyment of using a car.

[RacerMike]

mwstewart said:

RacerMike said:

Not entirely true in this case. IPB/Brake By Wire isn't really taking any control away from the driver, and it's introduction isn't to do so. It's primary drivers are a reduction in weight (good) and complexity (good), and improvement in performance (needed to deliver some of the safety features needed by incoming legislation) and cost.

Before worrying too much, I'd recommend having a go. Honestly, it feels like a big step on from the semi by wire systems currently around, and it highlights as well that no brake system for the last 30 years has really had any actual brake feel. I'd argue that you don't actually get any 'brake' feel with any servo assisted pedal as the force variation is way too small to make it through the assistance. My Caterham race car arguably did have the potential to feel when a wheel was about to lock, but I can't honestly say if that was entirely through the pedal. It was probably a combination of everything.

I did say to facilitate, however the development of these systems is entirely due to control (or lack of it). I would argue that overall system complexity is higher but the packaging is smaller.

With the exception of the throttle plate, I don't think there is a better driver control interface than a physical one, but my measure of performance is interaction and feel rather than safety and cost. I take the (simple) view that brakes and steering are basic systems that were perfected many years ago, and the advances we have seen, and continue to see today, are driven by requirements other than those that will reasonably increase my enjoyment of using a car.

Mechanically and electrically it’s a lot simpler. The way it generates brake pressure for ESP is also a lot simpler and more natural too, so it has the potential to be a lot more refined and a lot better controlled when in ABS or ESP Control.

The drivers for brake by wire genuinely aren’t to do with removing control from the driver. It provides a good solution that covers a multitude of drive types (which can also include regen) in a lighter package that gives much more consistency. You’re not really losing out on anything you had, but you are gaining in many other areas.

Honestly, have a go in a car that has it, and you might be surprised.

[mwstewart]

RacerMike said:

Mechanically and electrically it’s a lot simpler. The way it generates brake pressure for ESP is also a lot simpler and more natural too, so it has the potential to be a lot more refined and a lot better controlled when in ABS or ESP Control.

The drivers for brake by wire genuinely aren’t to do with removing control from the driver. It provides a good solution that covers a multitude of drive types (which can also include regen) in a lighter package that gives much more consistency. You’re not really losing out on anything you had, but you are gaining in many other areas.

Honestly, have a go in a car that has it, and you might be surprised.

I'm loosing a direct physical connection to one of the key driver interfaces. To me, that is loosing something significant.

[mackie1]

I assume there's some kind of fail safe if for example the brake pedal itself was to malfunction or electrical power is completely lost?

[RacerMike]

mwstewart said:

I'm loosing a direct physical connection to one of the key driver interfaces. To me, that is loosing something significant.

Just playing devils advocate with you here, so don’t take it the wrong way as I’m not totally disagreeing with you....but....

Are you really directly connected to the brakes even in a traditional system? With all the hydraulic lines, fluid, compliance etc, the effort you put in at the pedal in any car that was made in the last 80 years, hasn’t really directly acted on the brake pads. Arguably the only cars with a direct connection are pre war things with rod brakes. As I said before, brake ‘feel’ is really just something we perceive based on the travel/force we apply to the brake pedal vs the deceleration response we get from the car.

I’m more inclined to agree with you if we’re talking about steering. There’s clearly a direct physical connection with the wheels with a steering wheel.

I suppose the counter question I could ask would be ‘what feedback through the brake pedal do you feel enhances your ability to drive a car?’

[mwstewart]

RacerMike said:

Just playing devils advocate with you here, so don’t take it the wrong way as I’m not totally disagreeing with you....but....

Are you really directly connected to the brakes even in a traditional system? With all the hydraulic lines, fluid, compliance etc, the effort you put in at the pedal in any car that was made in the last 80 years, hasn’t really directly acted on the brake pads. Arguably the only cars with a direct connection are pre war things with rod brakes. As I said before, brake ‘feel’ is really just something we perceive based on the travel/force we apply to the brake pedal vs the deceleration response we get from the car.

I’m more inclined to agree with you if we’re talking about steering. There’s clearly a direct physical connection with the wheels with a steering wheel.

I suppose the counter question I could ask would be ‘what feedback through the brake pedal do you feel enhances your ability to drive a car?’

That's fine, it's a good question: for the purposes of this discussion it can be considered direct, or direct enough to provide a range of information through the pedal. The pedal is directly impacted by the activity between disc and pad. Some examples:

- The feel of different disc types, be they carbon, drilled, or plain etc.;
- The difference in feel between hot/cold pads and discs - especially overheated ones and the signs of onset thereof;
- The feel from different characteristics in pad and disc compounds, and the change in feel and response throughout the stroke of the master cylinder;
- The change in feel of worn discs - be it pad deposits, or warping (or out of true hubs) - this is especially true for drilled iron discs.

The nuances in feedback are really important, but I understand that to the general market they are not: a linear, consistent behaviour is more important than feedback on a mixed range of operating characteristics and conditions.

[Escort Si-130]

Very interesting bit of info.

RacerMike said:

Clever bit of marketing this. They're using the Bosch IPB (Integrated Power Brake) like most of the industry in the coming years which replaces the ABS, Brake Booster and Master Cylinder with a 'one box' solution. Main drivers are a focus on efficiency and switch to hybridisation (the IPB allows easy integration of regen braking) and the addition of Level 2+ ADAS features that need full brake control.

BMWs involvement in this will extend along the lines of deciding the brake pedal map (the pedal isn't directly connected to anything other than a pedal feel simulator during normal braking) and the stability control calibration. You get the ability to add selectable maps for free effectively as it's 'just' a pedal travel/force curve.

Alfa already have the Continental equivalent on the Gulia and Stelvio, and the majority of the other OEMs will be using this or similar in the coming Model Year.

https://www.bosch-mobility-solutions.com/en/produc...

An interesting by-product of the tech is the removal of feedback through the pedal. So you get no vibration during ABS activation, and, as mentioned, no sense that the brakes are fading. Whether you see this as good or bad is entirely personal. For me....I quite like the feedback that you're close to the limit of braking when the ABS starts to control the wheels (although having driven quite a bit with an IPB recently, you can still sense its activation through the steering and the noise of the brake modulation) but the idea that you have no idea when there's fade is a little un-nerving. First thing you'd know about it would be the car failing to stop. I assume BMW have implemented some warning or powertrain de-rate to counter this though.

Edited by RacerMike on Thursday 9th May 12:58

[RacerMike]

mwstewart said:

RacerMike said:

Just playing devils advocate with you here, so don’t take it the wrong way as I’m not totally disagreeing with you....but....

Are you really directly connected to the brakes even in a traditional system? With all the hydraulic lines, fluid, compliance etc, the effort you put in at the pedal in any car that was made in the last 80 years, hasn’t really directly acted on the brake pads. Arguably the only cars with a direct connection are pre war things with rod brakes. As I said before, brake ‘feel’ is really just something we perceive based on the travel/force we apply to the brake pedal vs the deceleration response we get from the car.

I’m more inclined to agree with you if we’re talking about steering. There’s clearly a direct physical connection with the wheels with a steering wheel.

I suppose the counter question I could ask would be ‘what feedback through the brake pedal do you feel enhances your ability to drive a car?’

That's fine, it's a good question: for the purposes of this discussion it can be considered direct, or direct enough to provide a range of information through the pedal. The pedal is directly impacted by the activity between disc and pad. Some examples:

- The feel of different disc types, be they carbon, drilled, or plain etc.;
- The difference in feel between hot/cold pads and discs - especially overheated ones and the signs of onset thereof;
- The feel from different characteristics in pad and disc compounds, and the change in feel and response throughout the stroke of the master cylinder;
- The change in feel of worn discs - be it pad deposits, or warping (or out of true hubs) - this is especially true for drilled iron discs.

The nuances in feedback are really important, but I understand that to the general market they are not: a linear, consistent behaviour is more important than feedback on a mixed range of operating characteristics and conditions.

Sorry for the delay. Meant to reply earlier but had a busy weekend!

I think your list has a mix of things that are genuinely affected by the fact the system is fully hydraulic vs BBW, and some that are actually more related to other factors that you perceive as being brake 'feel' when they're more related to other factors which BBW wouldn't influence.

The one particular point I agree with you wouldn't be fed back via BBW is:

- The change in feel of worn discs - be it pad deposits, or warping (or out of true hubs) - this is especially true for drilled iron discs.

There would need to be some sort of feedback on this, but I'd argue that all of those things you mention are not positive things. They're error states that result from poor foundation brake design. There are always ways around warping and pad deposits (like correct sizing of discs and calipers, which BMW seem particularly bad at!).

To take the other points though:

- The feel of different disc types, be they carbon, drilled, or plain etc.

I'm not convinced that this is really something you feel through the pedal though. The 'abruptness' of CCMs is usually due to the fact that most cars that run them have to run logic that primes the calipers before you hit the pedal. To run CCMs you need high roll back calipers to ensure the pad is pulled back off the disc otherwise you get all sorts of efficiency and thermal issues. Without the pump prime, you get really inconsistent pedal travel which results in people 'under' braking in some instances as they don't realise they need press the pedal further. It's the same sort of issue that race cars have after running over kerbs which means the driver needs to pump the pedal down the straight.

You could easily just apply the same pedal travel map to a BBW system though. So the CCMs would still react the same to the same amount of pedal travel.

- The difference in feel between hot/cold pads and discs - especially overheated ones and the signs of onset thereof

Only really prevalent in really aggressive pads. You would however get the same effect with BBW though in my opinion. The stroke of the pedal isn't self compensating (i.e. it doesn't map pedal travel to deceleration) so you'd still need to push further/harder with cold track pads. You'd therefore still get the impression that they felt 'wooden' or 'cold'. What you wouldn't feel though is fade, as there's a specific 'fade compensation' logic which is believed to be preferable so inexperienced drivers don't panic and feel like the car won't stop. Whether this is a good thing remains to be seen IMO....I'd rather know the pads were getting too hot, but then as you said....we're in the minority for this.

- The feel from different characteristics in pad and disc compounds, and the change in feel and response throughout the stroke of the master cylinder

Again, I'm pretty confident you'd feel this still with BBW. Or at least you'd feel what the force/stroke curve has been tuned to. This isn't any different to a normal hydraulic system though. The guys who work on brake refinement/performance have, for decades, tuned the vacuum booster, master cylinder and pad compound to achieve a specific reaction to pedal stroke/force. The 'progressiveness' of the brakes in a Porsche isn't an accident. Everything has been tuned to deliver the same linearity as that's what defines the DNA of a Porsche's braking system. It's the same for Audi and VW. Their engineers choose that 'over servo'd' feel as most owners will perceive it as meaning the brakes are 'powerful'. It's a key attribute for them. Delivering this via a vacuum booster/hydraulic master cylinder is no different to delivering it with an electric booster and a pedal travel/force curve.

I'm 100% in agreement with you that there are some fringe things that you or I might feel at the outer edges of performance. I would really rather have the ability to feel when I'm on the edge of ABS for track driving....it makes threshold braking a lot easier! But even things like hot pads are actually something you hear or feel through the seat more than the brake pedal. You'd still have that with BBW.

As I said before, have a go in the M8 when it comes out and see what you think. I honestly don't think you'll find it as 'fake' as you fear. I genuinely think that it already provides better 'feel' than many traditional setups out there as you don't get the kind of pedal corruption you get with a hydraulic system running modern ABS/VDC. A good example would be that on track, after a Stability Control intervention, the next pedal apply is often different due to the fact that there will be some residual pressure left after the ABS pump run. This isn't a particularly good thing, and has no real benefit to the driver. A BBW system would feel the same as it did before the intervention.