Looking deeper into Big Brake Upgrades

[centurion]

This article is excellent reading for anybody considering BBKs. Now, some clarification needed. Discuss in terms of BMW cars if possible.

StopTech : Balanced Brake Upgrades

EBD

Electronic Brakeforce Distribution (also referred to as DRP, dynamic rear proportioning) - An electro-mechanical control system designed to monitor and influence rear wheel dynamics, and ultimately foundation brake (front-rear) balance. In so many words, the EBD utilizes the ABS hardware to function as an "intelligent brake proportioning valve." Unlike a traditional mechanical proportioning valve which is limited by design to one kneepoint and slope, the EBD algorithm relies on closed-loop feedback to continuously monitor rear wheel slip, adjusting brake line pressure to the rear wheels as appropriate.

The brake line pressure thing - serious??? Seems to be not compatible with their statement that it uses ABS hardware, coz I thought most ABS is just 1 or 0, brake or don't brake. The Bosch ABS controller really so smart???

And if really so smart, why the need for the next paragraph `to tune the ABS/TCS/ESP' since brake balance is more than sufficiently handled by the intelligent brake proportioning valve?

Technology Dependency - ABS/TCS/ESP

The calibration of modern ABS/TCS/ESP is a complex and time consuming processes entailing the setting, or "tuning," of literally thousands of algorithm variables. These variables define the base vehicle characteristics (braking system included), control limits, and expected vehicle reaction to control activity. For this reason, one control algorithm may be utilized on several applications, but each vehicle requires its own unique variable set, or table.

Taking this into consideration, does not the introduction of a BBK in front, screw up the balance and destroy the tuning? If the tuning is destroyed, wouldn't the braking distance be screwed worse because of the inability of the rear tyres to be used to max traction?

And there is a local post here by the disreputable pointing to some resources which I can't find online and the guy can't find it too. Which I don't quite agree that he place so much faith in the EBD especially after Shaun already say not all EBD is alike, much less a Scion tC EBD, unless Denso > Bosch: Where can I change my rear brakedisc? - Carma Online Forums

More resources:

Extended stability control: suppliers are adding greater functionality to electronic stability control systems to improve safety and entice car buyers to check the ESC option box Automotive Design & Production - Find Articles
Extended stability control: suppliers are adding greater functionality to electronic stability control systems to improve safety and entice car buyers to check the ESC option box

Wolfgang's ML Page: ABS to ESP
Charts for ABS pressure and braking force shows variability

Wow if all this is true then we can upgrade to BBKs with impunity and the bloody Stoptech article is FUD.

Shaun, come in please and comment.

 

[centurion]

Re: Looking deeper into Big Brake Upgrades

upz after yesterday's forum crash.

 

[FiftyFive]

Re: Looking deeper into Big Brake Upgrades

Hi CaySman... theories aside... in layman butt and drive feel... going to the track with BBKs and without are simply two worlds apart... especially so after a couple of laps on the track... charging down the straight towards turn 1at Sepang with stock brakes (heated) is a very very hairy affair....

 

[centurion]

Re: Looking deeper into Big Brake Upgrades

sure and definitely. BBKs additional mass dissipates more heat allowing you to lap more and maintain the same braking power. BUT there is a possibility that some BBKs may introduce a longer braking distance, unless EBD takes care of the balance issues.

 

[Shaun]

Re: Looking deeper into Big Brake Upgrades

Sorry missed this somehow. Little time to read now but will maybe on the weekend and reply. For now will say that there are always adaptive control strategies and it is developing fast. Usually by the time something of this nature goes to press and becomes common knowledge, it has already moved on.

As mentioned in other related thread previously (forgot subject), the old Stoptech article doesn't even consider adaptive control. It is simple PID type thing applied to wheelspeeds and line pressure control. There is no need to watch pressure directly, in fact it would be inferior in some ways because it doesn't take into account everything between the line and the ground-tire interface. Watching wheelspeeds includes everything up to the tire, and then has to make some assumptions about tire properties. Can't cover the large range of tire properties, so has to be compromised somewhat. Adaptive helps fill in the gap between one size fits all and actual, but still not perfect because of reaction time though theoretical imperfection because with modern electronics the times are reduced to about nothing.

There is always a desire to get the hardware as close to being optimal for the job as possible because you want efficiency and safety in the systems, and speed of response. The closer you are to perfect the first time, the smaller (hence faster) the subsequent corrections in any adaptive control.

The OEMs will cater for the usual tire, pad and line changes, etc. through adaptive control, or at least slap margin of safety in the direction of safe (forward bias)... the cheap route.

How active or reactive the system is a matter of time and money. The technnology has existed for a long time in other areas. Can't speak BMW specific because in recent years haven't followed marque-specific technology except occasionally in spots.

Hopefully this answers the main questions.. will read the links later.

 

[centurion]

Re: Looking deeper into Big Brake Upgrades

Thanks. In short, adaptative only to a certain extent. The cheap route (forward Bias) always result in the rear wheel not working hard enough. Result in lousy braking distance. So, even for stock brakes in some marques, looking at the braking distance and weight of the car, the adaptative doesn't seem to be working too well.

If so, that means the Stoptech article still mostly correct, and BBK will result in longer stopping distance, but more consistent over several laps.

 

[Shaun]

Re: Looking deeper into Big Brake Upgrades

So, even for stock brakes in some marques, looking at the braking distance and weight of the car, the adaptative doesn't seem to be working too well.

Or they don't have it and are just doing the cheap thing.

If so, that means the Stoptech article still mostly correct, and BBK will result in longer stopping distance, but more consistent over several laps.

Only if there is no adaptation at all, or there is only really bad adaptation. IMO both are improbable in modern cars so I think the Stoptech article is a little outdated. It is still good advice though because of reasons mentioned in previous post.

 

[centurion]

Re: Looking deeper into Big Brake Upgrades

nowadays, since people are more savvy, auto manufacturers should reveal more on their electronics strategies, like what is liked to what etc.

as of now, it is all a BLUR. Eg. ZF 6 speed auto gearbox used in Jag XK, 335 and Maser GT, WHY is the downshift rev-match blip (instead of generic blip) active in the XK and GT but not in the 335? How to activate it? They're all sharing the same electronics! you paid for it, why not get the full benefit?

Same as this case - is the adaptative brake pressure distribution good enough in any car to take aftermarket BBKs??? Nobody knows for sure, testing is done by BBK manufacturers only, with a risk of bias ...

 

[Shaun]

Re: Looking deeper into Big Brake Upgrades

Same as this case - is the adaptative brake pressure distribution good enough in any car to take aftermarket BBKs??? Nobody knows for sure, testing is done by BBK manufacturers only, with a risk of bias ...

Yeah you'll never reallly know unless the manufacturer publishes the right information, you know a guy working on the inside, or you have dedicated aftermarket companies that really do their research and talk specifically about certain models with confidence because they've put the time in to find out. If Stoptech had real data that showed the problem you can be sure it would be up in a paper with line pressure or wheel speed traces, deceleration distances, on a specific model, brand X vs their own brakes. Instead you have a paper generalizing and saying this "can" "in extreme cases" upset things and not even considering how simple it is to make smart controls nowadays to where if you were calculate the distances travelled in the time it takes to run through a few closed loop corrections and get control back to standard, it would be negligible.. even assuming the critical ratios were far off. I'm pretty sure too that if they found a problem like that, it would be with a real small and shady operation, not any one of their main competitors or any of the big names.

The good news is that to build a brake system based on a larger rotor and larger piston number or area, that has identical P-V P-T ratios to stock, is not rocket science. You could do it yourself in a couple hours. A design engineer with a spreadsheet or two.. minutes. Also, to test a system as installed on the car, is easy enough. You could do it by plain deceleration, stopping distances, or line pressure or wheel speed logs. First two are simpler and cheap.

The cautionary message and advice are all good, but stretched to create a selling point which IMO does not exist against competitors in the same price range, and possibly not with any modern performance conscious car manufacturer that has had its software engineers spend a very small amount of time (days) developing a program that can be applied across its entire model range to make all brake-based systems adaptable.