SCBS Saved my @ss!!

Kayger12

Member
:
'14 AWD GT w/Tech
So if you were standing on the brake to the point where your leg was hurting, why was ABS not activated? It certainly would have been in my 2013 without SCBS.

I'm guessing because in that short distance at that low speed on that dry friction surface the wheel didn't stop spinning to trigger the abs. It surprised me that the abs didn't kick in and that I didn't get wheel lock.

ABS issue actually crossed my mind. I took it out today-- higher speed on dry surface this morning and med/low speed on wet surface after it started raining today both triggered the abs as I would expect.

(dunno)
 

Dr_Watson

Member
:
2106 CX5 2.2D AWD MT 175PS, Tech pack, Sunroof, full LED
Is this addressed to me? I didn't say my ABS only works at low speeds. I said it would have worked at that low a speed (as well as any other speed)!

No, the op. At any speed, any driver should be able to trigger the abs in an emergency stop on any surface I would imagine. My guess is the feeling of the car braking harder is possible when at low speed simply because there was more grip which gave the false sense of the brakes working harder.
 
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Kayger12

Member
:
'14 AWD GT w/Tech
No, the op. At any speed, any driver should be able to trigger the abs in an emergency stop on any surface I would imagine. My guess is the feeling of the car braking harder is possible when at low speed simply because there was more grip which gave the false sense of the brakes working harder.
The increased braking was the result of the brake assist feature as evidenced by the fact that the braking increased precisely when the brake pedal depressed further when the scbs activated.

There wasn't a feeling of increased braking— there was increased braking.
 

Dr_Watson

Member
:
2106 CX5 2.2D AWD MT 175PS, Tech pack, Sunroof, full LED
SCBS is deactiveted if the brake pedal is already being pressed according to some docs I read. I can't see how it can apply more force! What if you are not within the scbs criteria, ie turning at the same time, then your emergency stop will never give you max stopping performance???
 
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CXVille

Member
:
2014 CX-5 GT & 3 i Touring
See my post above. If I didn't experience it I would have thought the same as you... But in this case I think it had everything to do with not hitting the car and apparently did provide additional brake pressure through the brake assist integration.

I'm a driving instructor with plenty of track time. I'm very familiar with the pedal/vehicle feel of abs kicking in.

Since you are a driving instructor you understand that ANY vehicle with properly operating brake system has more than enough capacity to lock up all wheels on dry pavement, or actuate ABS. Let me repeat, ANY modern vehicle.

Now the ABS, stability control, traction control, and a myriad of other "features" (ABS, SBS, SCBS, BFD and others) get between your foot and the brake pressure applied to the pads. I don't know about the CX5, but I know plenty of other cars modulate the brake pressure based on what they THINK you are trying to do. My E36 M3, while under heavy sustained braking, like T10A at Road Atlanta, coming down from 125 mph or so, will actually kick back at me, and move the brake pedal back towards me. And this is a relatively ancient car at 15 years old.

Since you have track experience, I suspect that this is what caused the problem, and it is possible that Brake Force Distribution (BFD) or some other "feature" saved you. Why would track experience create your problem? Because most experienced instructors have honed their skills over years of on track experience, to NOT activate ABS and to modulate the brake pedal accordingly. Unfortunately, with all of the safety features the pedal feel on many vehicles is impacted.

You are implying that you were unable to press the brake pedal hard enough to engage ABS and achieve maximum braking force, and the car intervened and added braking force. Others have said they think that SCBS won't activate with the brakes applied. I don't know. I only know that it can't miraculously increase braking force if you are applying adequate force to the pedal. It *might* increase braking force if you are not applying adequate force to lock the wheels and engage ABS..
 
:
was 175ps Mazda CX-5 Auto AWD Sport Nav, now 190ps DSG Tiguan 4M
I thought the same thing, but it definitely kicked in while I was already braking.

After looking into it I found out that the scbs system uses brake assist to provide additional braking force (page 4-76 of the owners manual). "when the driver depresses the brake pedal while the system is in the operating range the brakes are applied firmly and quickly to assist (Brake assist (SCBS brake assist))"

Mazda describes brake assist on their website as follows

"Sometimes, although drivers press the brake pedal as hard as they can, it may not be sufficient. Brake Assist measures the speed at which the brake pedal is pressed and the braking pressure and when the force is judged to be insufficient the system compensates by applying additional pressure."

Well put.
 
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was 175ps Mazda CX-5 Auto AWD Sport Nav, now 190ps DSG Tiguan 4M
Since you are a driving instructor you understand that ANY vehicle with properly operating brake system has more than enough capacity to lock up all wheels on dry pavement, or actuate ABS. Let me repeat, ANY modern vehicle.

Now the ABS, stability control, traction control, and a myriad of other "features" (ABS, SBS, SCBS, BFD and others) get between your foot and the brake pressure applied to the pads. I don't know about the CX5, but I know plenty of other cars modulate the brake pressure based on what they THINK you are trying to do. My E36 M3, while under heavy sustained braking, like T10A at Road Atlanta, coming down from 125 mph or so, will actually kick back at me, and move the brake pedal back towards me. And this is a relatively ancient car at 15 years old.

Since you have track experience, I suspect that this is what caused the problem, and it is possible that Brake Force Distribution (BFD) or some other "feature" saved you. Why would track experience create your problem? Because most experienced instructors have honed their skills over years of on track experience, to NOT activate ABS and to modulate the brake pedal accordingly. Unfortunately, with all of the safety features the pedal feel on many vehicles is impacted.

You are implying that you were unable to press the brake pedal hard enough to engage ABS and achieve maximum braking force, and the car intervened and added braking force. Others have said they think that SCBS won't activate with the brakes applied. I don't know. I only know that it can't miraculously increase braking force if you are applying adequate force to the pedal. It *might* increase braking force if you are not applying adequate force to lock the wheels and engage ABS..

So why was the SCBS light on if it didn't operate?
I might add on this car I have never had the ABS operate, and I am familiar with it operating in both dual channel and four channel systems, having had cars with ABS since 1991 on a Nissan Primera.
 

CXVille

Member
:
2014 CX-5 GT & 3 i Touring
So why was the SCBS light on if it didn't operate?
I might add on this car I have never had the ABS operate, and I am familiar with it operating in both dual channel and four channel systems, having had cars with ABS since 1991 on a Nissan Primera.

I said I didn't know if it would "activate" with the brakes activated. Another member indicated this may be the case. I don't know. Just because the light is on doesn't mean in actually increased braking force, only that it was activated because of certain parameters.

My point is simple. Almost any driver, and especially one with considerable track driving experience, has more than enough force to lock up the wheels on all four wheels on a modern car, or activate ABS. The statement that SCBS increased braking force defies physics, unless the driver was not applying adequate braking force. SCBS can NOT reduce stopping distances beyond that capable from a driver's input. It can react quicker. It can be more consistent. It can't counter act physics. I do not want anyone on here to believe that SCBS will reduce braking distances. It won't.
 

Kayger12

Member
:
'14 AWD GT w/Tech
Since you are a driving instructor you understand that ANY vehicle with properly operating brake system has more than enough capacity to lock up all wheels on dry pavement, or actuate ABS. Let me repeat, ANY modern vehicle.

Now the ABS, stability control, traction control, and a myriad of other "features" (ABS, SBS, SCBS, BFD and others) get between your foot and the brake pressure applied to the pads. I don't know about the CX5, but I know plenty of other cars modulate the brake pressure based on what they THINK you are trying to do. My E36 M3, while under heavy sustained braking, like T10A at Road Atlanta, coming down from 125 mph or so, will actually kick back at me, and move the brake pedal back towards me. And this is a relatively ancient car at 15 years old.

Since you have track experience, I suspect that this is what caused the problem, and it is possible that Brake Force Distribution (BFD) or some other "feature" saved you. Why would track experience create your problem? Because most experienced instructors have honed their skills over years of on track experience, to NOT activate ABS and to modulate the brake pedal accordingly. Unfortunately, with all of the safety features the pedal feel on many vehicles is impacted.

You are implying that you were unable to press the brake pedal hard enough to engage ABS and achieve maximum braking force, and the car intervened and added braking force. Others have said they think that SCBS won't activate with the brakes applied. I don't know. I only know that it can't miraculously increase braking force if you are applying adequate force to the pedal. It *might* increase braking force if you are not applying adequate force to lock the wheels and engage ABS..

The electronic gremlins argument is correct, but you're missing the part about inertia and fluid dynamics with the hydraulic fluid. The whole reason brake assist systems were engineered was to overcome the delay in pressure build under very forceful application. Under "panic braking" (I hate that term), fluid dynamics makes the braking less effective. That's the whole reason auto manufacturers developed brake assist in the first place. Pressing the brake pedal as hard as you can will take longer to build the same hydraulic pressure than pressing it more gradually. Take a look. Not Mazda but it explains it succinctly.

The brake feel change mentioned at 1:15 of the video describes exactly what I experienced.

And again, from Mazda: "Sometimes, although drivers press the brake pedal as hard as they can, it may not be sufficient. Brake Assist measures the speed at which the brake pedal is pressed and the braking pressure and when the force is judged to be insufficient the system compensates by applying additional pressure."

My only remaining question is why the brake assist didn't kick in until the SCBS activated. My guess at this point would be the low speed combined with perhaps too controlled an application of the brake. I really don't know.

"I only know that it can't miraculously increase braking force if you are applying adequate force to the pedal." To the contrary-- that's exactly what brake assist was designed to do and does do. As others have said (though, for different reasons) it's physics.

I said I didn't know if it would "activate" with the brakes activated. Another member indicated this may be the case. I don't know. Just because the light is on doesn't mean in actually increased braking force, only that it was activated because of certain parameters.

My point is simple. Almost any driver, and especially one with considerable track driving experience, has more than enough force to lock up the wheels on all four wheels on a modern car, or activate ABS. The statement that SCBS increased braking force defies physics, unless the driver was not applying adequate braking force. SCBS can NOT reduce stopping distances beyond that capable from a driver's input. It can react quicker. It can be more consistent. It can't counter act physics. I do not want anyone on here to believe that SCBS will reduce braking distances. It won't.

Again, you're missing the whole physics of fluid dynamics and hydraulic pressure in the system during rapid, forceful pedal travel. It isn't counteracting physics-- it's proving physics. And yes, if it activates the brake assist the SCBS will most certainly reduce braking distance. Every test done with EBA shows this. It can load the system with more hydraulic pressure faster than a human.
 
:
was 175ps Mazda CX-5 Auto AWD Sport Nav, now 190ps DSG Tiguan 4M
I said I didn't know if it would "activate" with the brakes activated. Another member indicated this may be the case. I don't know. Just because the light is on doesn't mean in actually increased braking force, only that it was activated because of certain parameters.

My point is simple. Almost any driver, and especially one with considerable track driving experience, has more than enough force to lock up the wheels on all four wheels on a modern car, or activate ABS. The statement that SCBS increased braking force defies physics, unless the driver was not applying adequate braking force. SCBS can NOT reduce stopping distances beyond that capable from a driver's input. It can react quicker. It can be more consistent. It can't counter act physics. I do not want anyone on here to believe that SCBS will reduce braking distances. It won't.

Are you sure about that?

From the link. " Active Braking Systems can reduce stopping distances by 45% in simulator trials "

http://www.howsafeisyourcar.com.au/Active-Braking-Systems/

This is a Mazda system.

https://www.youtube.com/watch?v=I8GA-l3Iwts#t=10
 
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Dr_Watson

Member
:
2106 CX5 2.2D AWD MT 175PS, Tech pack, Sunroof, full LED
Agree that at higher speeds, it may not be that easy to activate the abs, but I have done a few emergency stops for fun, I like to see how a car handles when I first buy it, plus I have done plenty track time and like to let my hair down occasionally, on all occasions from any speed, I can activate the abs, especially low speeds as this story describes. If the abs is active then the is no way any other system can then help reduce the stopping distance, the explanation in this case is that full braking was not applied during the whole stop so the system activated. Pretty smart system if you ask me and nice to have. Interesting reading those articles above.

Just out of interest, did your hazard warning lights activated, mines do when I stamp the brakes.
 

Kayger12

Member
:
'14 AWD GT w/Tech
Agree that at higher speeds, it may not be that easy to activate the abs, but I have done a few emergency stops for fun, I like to see how a car handles when I first buy it, plus I have done plenty track time and like to let my hair down occasionally, on all occasions from any speed, I can activate the abs, especially low speeds as this story describes. If the abs is active then the is no way any other system can then help reduce the stopping distance, the explanation in this case is that full braking was not applied during the whole stop so the system activated. Pretty smart system if you ask me and nice to have. Interesting reading those articles above.

Just out of interest, did your hazard warning lights activated, mines do when I stamp the brakes.

They did not. That's a great option. The BMW has something similar-- when the abs activates it flashes the brake lights repeatedly for something like 5 seconds. Had to have a buddy activate it through the coding software. Apparently they're not supposed to allow that option to be activated in the US for some reason.
 
There is a correlation/causation problem going on here.

Presumably the driver is someone within a couple standard deviations of average leg strength. Vanilla, low-tech braking systems are designed to have enough force to lock up your wheels, so an extra "boost" beyond the boost of simply having power brakes is nonsense.

When you feel the pedal dropping further during the emergency braking, that is *not* caused by SCBS or the "dramatic increase of braking force". That's most likely a byproduct of the ABS solenoid reducing your braking pressure to avoid locking up the wheels. Any effect SCBS would have had would exist before you applied the pedal at full force, not after.

The SCBS system light will come on because your situation satisfies all the conditions for SCBS activation. Assuming you're in reasonably good health, either your perception of "dramatic increase in braking force" and "pedal sinking further" was not caused by the SCBS activation, or Mazda is in the business of building defective power brakes.
 

Kayger12

Member
:
'14 AWD GT w/Tech
There is a correlation/causation problem going on here.

Presumably the driver is someone within a couple standard deviations of average leg strength. Vanilla, low-tech braking systems are designed to have enough force to lock up your wheels, so an extra "boost" beyond the boost of simply having power brakes is nonsense.

When you feel the pedal dropping further during the emergency braking, that is *not* caused by SCBS or the "dramatic increase of braking force". That's most likely a byproduct of the ABS solenoid reducing your braking pressure to avoid locking up the wheels. Any effect SCBS would have had would exist before you applied the pedal at full force, not after.

The SCBS system light will come on because your situation satisfies all the conditions for SCBS activation. Assuming you're in reasonably good health, either your perception of "dramatic increase in braking force" and "pedal sinking further" was not caused by the SCBS activation, or Mazda is in the business of building defective power brakes.

I've been through more than my share of ABS activations. I know what the pedal modulations feel like. This was not it.

Did you even read/watch the threads dealing with hydraulic pressure? If you did, you would see extra braking pressure is not nonsense. If you read it and still think it's nonsense then we can just move on...
 
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:
was 175ps Mazda CX-5 Auto AWD Sport Nav, now 190ps DSG Tiguan 4M
There is a correlation/causation problem going on here.

Presumably the driver is someone within a couple standard deviations of average leg strength. Vanilla, low-tech braking systems are designed to have enough force to lock up your wheels, so an extra "boost" beyond the boost of simply having power brakes is nonsense.

When you feel the pedal dropping further during the emergency braking, that is *not* caused by SCBS or the "dramatic increase of braking force". That's most likely a byproduct of the ABS solenoid reducing your braking pressure to avoid locking up the wheels. Any effect SCBS would have had would exist before you applied the pedal at full force, not after.

The SCBS system light will come on because your situation satisfies all the conditions for SCBS activation. Assuming you're in reasonably good health, either your perception of "dramatic increase in braking force" and "pedal sinking further" was not caused by the SCBS activation, or Mazda is in the business of building defective power brakes.

Why don't you read the links.
Or post some of your own with counter arguments.
 
I've been through more than my share of ABS activations. I know what the pedal modulations feels like. This was not it.

Did you even read/watch the threads dealing with hydraulic pressure? If you did, you would see extra braking pressure is not nonsense. If you read it and still think it's nonsense then we can just move on...

Yes, I watched the video and read the thread, and again I'll reiterate, the systems are designed to help you get to full braking force. In your near-miss story, you would have already achieved full braking force before you felt the delayed sensation of the pedal drop. EBA systems are all about managing brake pressure more effectively before you get to the point where you're straining your calf muscles.

http://en.wikipedia.org/wiki/Emergency_brake_assist


If an emergency develops, a slow reaction and less than maximum braking input could result in insufficient time or distance to stop before an accident occurs.

EBA is designed to detect such "panic stops" and apply maximum braking effort within milliseconds. It interprets braking behaviour by assessing the rate that the brake pedal is activated.

If the system identifies an emergency, it automatically initiates full braking faster than any driver can move their foot. Emergency stopping distances can be shortened, reducing the likelihood of accidents – especially the common "nose to tail" incident.


If you're already stomping at the pedal with enough force to strain your calf muscles and feeling a later change in the brake pedal pressure, if SCBS did anything at all, it would have happened long before you felt the shift in the pedal travel.
 

Kayger12

Member
:
'14 AWD GT w/Tech
Yes, I watched the video and read the thread, and again I'll reiterate, the systems are designed to help you get to full braking force. In your near-miss story, you would have already achieved full braking force before you felt the delayed sensation of the pedal drop. EBA systems are all about managing brake pressure more effectively before you get to the point where you're straining your calf muscles.

http://en.wikipedia.org/wiki/Emergency_brake_assist


If an emergency develops, a slow reaction and less than maximum braking input could result in insufficient time or distance to stop before an accident occurs.

EBA is designed to detect such "panic stops" and apply maximum braking effort within milliseconds. It interprets braking behaviour by assessing the rate that the brake pedal is activated.

If the system identifies an emergency, it automatically initiates full braking faster than any driver can move their foot. Emergency stopping distances can be shortened, reducing the likelihood of accidents – especially the common "nose to tail" incident.


If you're already stomping at the pedal with enough force to strain your calf muscles and feeling a later change in the brake pedal pressure, if SCBS did anything at all, it would have happened long before you felt the shift in the pedal travel.

There was no "long before". This didn't happen over 5 minutes-- it was a matter of maybe 3 seconds from start to stop. The time from scsbs activation to stop was probably less than 2 seconds. I was pushing with full pressure, the brake pressure was building against the hydraulic pressure of me slamming the brake. It appears the brake assist was triggered by the scbs (which we know are integrated systems with the CX-5), allowed an increase in brake pressure, and the pedal drop, and the increase in braking force, and the sensation of increased braking.

I'm comfortable with that explanation at this point. I don't have a desire to get in a back and forth with you. Feel comfortable in your assessment and belief. I don't need everyone to agree. It's clear neither of us is going to change the other's mind.

Good discussion.
 

Pipemajor

Hoot Mon!
:
Minnesota
:
2017 CX-5 GT AWD
I've had SCBS activate on me at least twice. Happens when I exit our controlled parking lot with a gate arm. I'll approach the gate, the arm starts to rise and I'll apply the throttle to exit. The system 'sees' the gate arm and SCBS engages with a noticeable scrunch sound and nearly threw my wife (who was belted) through the windshield.

It's a powerful stopping activation.
 

CXVille

Member
:
2014 CX-5 GT & 3 i Touring
Are you sure about that?

From the link. " Active Braking Systems can reduce stopping distances by 45% in simulator trials "

http://www.howsafeisyourcar.com.au/Active-Braking-Systems/

This is a Mazda system.

https://www.youtube.com/watch?v=I8GA-l3Iwts#t=10

You a politician? Because you sure misuse quotes like one. This thread is about how a driver observed increased braking force AFTER he applied the brakes in a panic situation. Your quote comes from activating the braking system BEFORE the driver using radar and similar look ahead techniques.

And the EBA system is active immediately - the Mazda video says "immediately applied on all four wheels".

So, back to my point - nothing in the vehicle will suddenly increase braking force just before impact. EBA and Active Braking Systems are designed to have almost immediate impact, not delayed as described in this thread.