SBC: The Ticking Time-Bomb

[Dieselman]

How can the force be greater than locking the wheel or causing the ABS to activate?

The tyre to road interface is what makes vehicles stop quickly, it doesn't matter what reserve of braking power one has, once the the wheel locks the brakes can do no more.

If teh cost is a minor proportion of what they are sold for then that says MB have been a bit disingenuous about the goodwill aspect and a bit disrespectful to the customers paying the full price.

Just like they have for corrosion claims. Even with the goodwill allocation the customer covers all the cost.

 

[Dryce]

How can the force be greater than locking the wheel or causing the ABS to activate?

That's not the point.

It's about response time to apply that full force.

 

[Dieselman]

That's not the point.

It's about response time to apply that full force.

Isn't that what BAS does?

 

[Dryce]

Isn't that what BAS does?

Yes.

Take an average driver and put them in a W211 pre and post facelift with same tyres and same road surface and have them come to an unexpected emergency stop.

I'd expect the pre-facelift SBC will consistently beat the post facelift BAS+ in terms of stopping distance.

BAS is a good system. But the powered SBC system should beat it - even 10 years on from its first introduction.

What if it was a trained driver. The gap would be closer probably - but it's likely the SBC car would still win.

 

[mersum1es]

My post #44 has a link which advertises SBC features...

I have asked earlier if that 'complete failure' happens, is there anything left? Documents states that there should be some brake force left in front wheels, but drivers with failed system has stated that pedal goes to floor... what I like to know is system working if pumping the pedal, like oldtimes had to do when your pedal hit the floor.

 

[Dieselman]

Take an average driver and put them in a W211 pre and post facelift with same tyres and same road surface and have them come to an unexpected emergency stop.

I'd expect the pre-facelift SBC will consistently beat the post facelift BAS+ in terms of stopping distance.

.

Do you have any evidence to back up that expectation.

I drive cars with both powered and BAS equipped brakes and although I find the effort required and lack of grab is a bit tedious in the regular servo cars, when BAS kicks in there is instant maximum braking, so no difference.

I do prefer the feel of powered brakes.

 

[Dieselman]

My post #44 has a link which advertises SBC features...

I have asked earlier if that 'complete failure' happens, is there anything left? Documents states that there should be some brake force left in front wheels, but drivers with failed system has stated that pedal goes to floor... what I like to know is system working if pumping the pedal, like oldtimes had to do when your pedal hit the floor.

The pedal shouldn't go to the floor as there is a backup unassisted front brake circuit.

If you have ever driven a heavy car without servo assisted brakes, you will know just how ineffective those brakes are.
iirc, the stopping power is 10% of normal stopping power under working SBC.

 

[bpsorrel]

Yes.

Take an average driver and put them in a W211 pre and post facelift with same tyres and same road surface and have them come to an unexpected emergency stop.

I'd expect the pre-facelift SBC will consistently beat the post facelift BAS+ in terms of stopping distance.

BAS is a good system. But the powered SBC system should beat it - even 10 years on from its first introduction.

What if it was a trained driver. The gap would be closer probably - but it's likely the SBC car would still win.

But none of that justifies a system that has a built in (expensive) limited lifespan which the potential customer is not made aware of before purchasing the car. If they honoured FOC repairs that would be a step in the right direction, but to now say "up yours loyal customers, you're on your own, despite our design flaw" is diabolical. (IMO)

Incredible arrogance by MB (again) and further reason to move on to another brand when the time comes.

 

[whitenemesis]

From own info...

The SBC provides the following advantages:

• Improvement in the metering of the required brake pressure, more precise and quicker.
• Shortening of stopping distance in particular for an emergency stop (improved Brake Assist function).
• Increase in active vehicle dynamics safety as the vehicle dynamics control systems of the antilock brake system (ABS) and Brake Assist (BAS), as well as acceleration slip regulation (ASR) and Electronic Stability Program (ESP) be used to the optimum extent.
• Leads to a more timely and comfortable stabilization vehicle during an ASR or ESP control.
• Takes care of more uniform wear on the brake pads and improves response characteristics of the brakes as a result of optimal braking force distribution between the front and rear wheels.
• Use of the brake power reserve of the rear axle by increasing the brake power share in the partial braking area and with a brake application from low speed by electronic brake force distribution (EBV).
• The electronic brake force distribution of the SBC systems leads to a more stable braking characteristics for optimum deceleration values when cornering by shifting the brake forces to the outer wheels.
• No reaction (vibration) on the brake pedal during ABS control intervention functions

 

[Dryce]

But none of that justifies a system that has a built in (expensive) limited lifespan which the potential customer is not made aware of before purchasing the car.

Well it was sort of mentioned in the sales blurb. But then so was Assyst+ and it's another rather strange MB invention with those service letters that aren't actually service designations.

However the rationale in the late nineties when they would have been commiting to designing in the system into the W210 successor might have been rather different. Engineers tend to be quite conservative and careful. So something hasn't worked out as anticipated I guess.

I wonder what they actually projected in terms of lifespan and lifecycle costs given that they knew from experience that some of the cars would have very high use (eg. taxis) right from the start.

 

[C240Sport97]

From own info...

The SBC provides the following advantages:

• Improvement in the metering of the required brake pressure, more precise and quicker.
• Shortening of stopping distance in particular for an emergency stop (improved Brake Assist function).
• Increase in active vehicle dynamics safety as the vehicle dynamics control systems of the antilock brake system (ABS) and Brake Assist (BAS), as well as acceleration slip regulation (ASR) and Electronic Stability Program (ESP) be used to the optimum extent.
• Leads to a more timely and comfortable stabilization vehicle during an ASR or ESP control.
• Takes care of more uniform wear on the brake pads and improves response characteristics of the brakes as a result of optimal braking force distribution between the front and rear wheels.
• Use of the brake power reserve of the rear axle by increasing the brake power share in the partial braking area and with a brake application from low speed by electronic brake force distribution (EBV).
• The electronic brake force distribution of the SBC systems leads to a more stable braking characteristics for optimum deceleration values when cornering by shifting the brake forces to the outer wheels.
• No reaction (vibration) on the brake pedal during ABS control intervention functions

which of these advantages absent on the conventional system that replaced SBC?

 

[bpsorrel]

Does anyone know what 300,000 brake applications equates to in years/mileage of an average usage car? (some town, some motorway driving)

 

[steve333]

Does anyone know what 300,000 brake applications equates to in years/mileage of an average usage car? (some town, some motorway driving)

^
If it was the old granny in front of me this morning then about 2k miles!

 

[Dryce]

Does anyone know what 300,000 brake applications equates to in years/mileage of an average usage car? (some town, some motorway driving)

It will depend significantly on the environment in which the car is used and also be dependent on driving style.

I reckon on a 20 mile cross country/suburban route I use the brake pedal around 40 times on average. I reckon I hear the pump about 5 times on that journey. (I'm a sad git - I think about these things).

That works out at 2 per mile on brake pedal or 0.25 per mile on pump actuations.

On urban journeys the figures will be a lot higher per mile - especially in very poor traffic flow conditions - say 10 to 15 per mile. Conversely motorway cruising will be a lot lower. Driving styles will significantly affect cross country figures depending on how a driver pushes and uses the brakes.

So urban taxi working in rushour averaging 10 per mile might reach 300,000 brake actuations in under 50,000 miles. OTOH a suburban / cross country commute averaging 2 per mile will last 150,000 miles.

I would add that what is counted may be pump actuations rather than brake actuations - so that may skew the numbers but not the principle. However I don't think that the range is likely to be far from reality - there were reports of early W211s needing pumps after just a few years and we also hear reports of people needing replacements well over 100,000. This may well be skewed for later cars because MB quietly played with the parameters when cars were updated during servicing.

 

[Stratman]

Does anyone know what 300,000 brake applications equates to in years/mileage of an average usage car? (some town, some motorway driving)

It was fitted to W211 cars between 2003 and 2006 and the messages have been mentioned on here for at least a couple of years, so that should give us a kind of idea.

 

[Dryce]

It was fitted to W211 cars between 2003 and 2006 and the messages have been mentioned on here for at least a couple of years, so that should give us a kind of idea.

I think the level of mentions will go up - even taking into account the likely upward trend as the vehicle population ages.

People who wouldn't otherwise participate in the forums will come here looking for advice/solution.

Whereas previously their dealer would have arranged the replacement FOC - masking the issue and hiding the apparent replacement rate to some degree.

 

[bpsorrel]

Do we know for a fact MB are no longer replacing FOC or is it just a rumour? Might still be worth trying with MB if the need arose..

 

[Deleted member 37751]

Do we know for a fact MB are no longer replacing FOC or is it just a rumour? Might still be worth trying with MB if the need arose..

*IF* your car has full Mercedes service history (on time and in date) and *IF* you have any sort of relationship with your main dealer, then you *SHOULD* qualify for a 'free' SBC pump.

There will of course be the odd exceptions to this either way, but it definately seems the way they are heading.

 

[bpsorrel]

Great. I score one out of two then..... (don't have a relationship of any kind with an MB dealer )

 

[Dryce]

Do we know for a fact MB are no longer replacing FOC or is it just a rumour? Might still be worth trying with MB if the need arose..

Was the 'fact' they they were previously replacing them FOC any less of a rumour? I don't think it was officialy stated by MB at any time - it was just the under-the-counter-policy-du-jour which appears to have been changed to a new under-the-counter-policy-du-jour but nobody really knew.