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1005 posts

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  # 995554 27-Feb-2014 15:16
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ubergeeknz:
clevedon:
Klipspringer: If all 4 wheels are locked up you have no speed. hence no ABS....

Its the same as all 4 sensors not working. Take them out and see what happens.

Are you trying to not understand?


Wrong, if any wheel locks under braking that wheel sensor signals the ABS computer which in turn signals the ABS pump and activates the system. It could be on one wheel or four - it does not matter.


Actually Klipspringer is correct, if all four wheels lock up at the same time the computer only knows that you are "stopped", not that the wheels are slipping.  It will not activate the pump.


The G sensors in a lot of vehicles will know the vehicle has momentum and if they are not fitted the speedo lets the ABS know the vehicle is in motion and activate the system. 

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  # 995557 27-Feb-2014 15:24
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clevedon:
ubergeeknz:
clevedon:
Klipspringer: If all 4 wheels are locked up you have no speed. hence no ABS....

Its the same as all 4 sensors not working. Take them out and see what happens.

Are you trying to not understand?


Wrong, if any wheel locks under braking that wheel sensor signals the ABS computer which in turn signals the ABS pump and activates the system. It could be on one wheel or four - it does not matter.


Actually Klipspringer is correct, if all four wheels lock up at the same time the computer only knows that you are "stopped", not that the wheels are slipping.  It will not activate the pump.


The G sensors in a lot of vehicles will know the vehicle has momentum and if they are not fitted the speedo lets the ABS know the vehicle is in motion and activate the system. 


I suppose that all depends on the make/model of the car.

Some cars may have it. Some cars may not. There are many types of ABS systems. Some types only have a single sensor. Some older vehicles only have ABS at the rear.

 
 
 
 


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  # 995558 27-Feb-2014 15:24
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surfisup1000:
Geektastic: I've noticed (on a related note) that the cars they use in adverts involving stopping quickly to avoid accidents invariably lack ABS.

My father had ABS in a Merc he bought in the 80's. Surely no cars exist 25 years later (other than classics) that lack this very basic safety feature? Even Triumph were fitting it to cars in 1972!


I was sceptical about your 1972 claim....but, googling it, sure , they were fitting abs to cars back then. 

Awesome!!


I just did some googling - out of curiosity.  Of the many features of a "modern" car ESC is possibly the only one which might be considered a "recent innovation".
These dates are for first commercial use in road cars as opposed to race cars, and in some cases (ie ABS) use in aircraft preceded migration to use in cars by many decades.

Disc Brake - 1902 (Lanchester)
Supercharger - 1923 (Mercedes)
DOHC - 1925 (or before, Sunbeam 3-litre)
Air conditioning - 1939 (Packard)
Auto transmission - 1940 (GM / Oldsmobile)
Petrol direct injection - 1955 (Mercedes)
EFI - 1957 (AMC / Rambler)
Seat Belts as standard feature - 1958 (Saab)
Turbocharger - 1962 (GM/ Oldsmobile)
ABS - 1966 (Jensen FF)
Airbag - 1971 (GM / Oldsmobile)
ESC - 1995 (Mercedes)



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  # 995559 27-Feb-2014 15:27
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clevedon:
ubergeeknz:
clevedon:
Klipspringer: If all 4 wheels are locked up you have no speed. hence no ABS....

Its the same as all 4 sensors not working. Take them out and see what happens.

Are you trying to not understand?


Wrong, if any wheel locks under braking that wheel sensor signals the ABS computer which in turn signals the ABS pump and activates the system. It could be on one wheel or four - it does not matter.


Actually Klipspringer is correct, if all four wheels lock up at the same time the computer only knows that you are "stopped", not that the wheels are slipping.  It will not activate the pump.


The G sensors in a lot of vehicles will know the vehicle has momentum and if they are not fitted the speedo lets the ABS know the vehicle is in motion and activate the system. 


G sensor, yes, however only some cars have these in the ABS system.  However given that a speedo only measures wheel rotation speed, it won't help in this situation.

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  # 995560 27-Feb-2014 15:27
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jarledb:
Klipspringer:
hehe thats where the braking skill comes into play ...


Breaking under those conditions without ABS you will want to pump brake, which means you will have all wheels locked from time to time.


This actually raises an interesting point.

So under these types of conditions, ABS actually takes this control away from the driver.

Or is it possible to "pump the break" on a vehicle with ABS when the ABS system has determined its better to not lock up the wheels?

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  # 995570 27-Feb-2014 15:44
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ubergeeknz:
clevedon:
ubergeeknz:
clevedon:
Klipspringer: If all 4 wheels are locked up you have no speed. hence no ABS....

Its the same as all 4 sensors not working. Take them out and see what happens.

Are you trying to not understand?


Wrong, if any wheel locks under braking that wheel sensor signals the ABS computer which in turn signals the ABS pump and activates the system. It could be on one wheel or four - it does not matter.


Actually Klipspringer is correct, if all four wheels lock up at the same time the computer only knows that you are "stopped", not that the wheels are slipping.  It will not activate the pump.


The G sensors in a lot of vehicles will know the vehicle has momentum and if they are not fitted the speedo lets the ABS know the vehicle is in motion and activate the system. 


G sensor, yes, however only some cars have these in the ABS system.  However given that a speedo only measures wheel rotation speed, it won't help in this situation.


The speedo does not instantly stop if all four wheels lock. The speedo sensor is gear driven inside the gearbox and does not instantly stop working when all four wheels lock (as said earlier - very rare) , a vehicle has to have momentum for the ABS to work.

Unless you pick up a stationary vehicle with the wheels locked with your foot on the brake and throw it out onto ice and let it slide - yes the ABS will not work.

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  # 995576 27-Feb-2014 15:51
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I drive a Honda Euro, here is how they define stability control

Vehicle Stability Assist (VSA)

Should the car deviate from its correct path, VSA activates to bring the car back on track.

Vehicle Stability Assist (or Electronic Stability Control) is designed to anticipate when the car is being driven either deliberately or inadvertently in such a way that a loss of front or rear tyre grip is about to occur.

During cornering, VSA determines if the car is deviating from its correct path.

The system monitors the speed of the car as well as the relative speed of each wheel, the amount of turn on the steering wheel and the yaw and lateral G-forces on the vehicle. Should the car deviate from its correct path, VSA activates to bring the car back on track by applying the brakes to any individual wheel or adjusting the engine output.

Traction Control - Enhancing VSA

Traction Control is part of the VSA (Vehicle Stability Assist) system.

When one or both driving wheels has insufficient traction due to a combination of throttle opening, cornering force and low grip levels of the road surface, the Traction Control system will automatically reduce engine power until traction is re-established.

 
 
 
 


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  # 995590 27-Feb-2014 16:17
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clevedon:

The speedo does not instantly stop if all four wheels lock. The speedo sensor is gear driven inside the gearbox and does not instantly stop working when all four wheels lock (as said earlier - very rare) , a vehicle has to have momentum for the ABS to work.

Unless you pick up a stationary vehicle with the wheels locked with your foot on the brake and throw it out onto ice and let it slide - yes the ABS will not work.


I realize we are off topic here so apologies. This is an interesting thread.

From my understanding the speedo gets its info from the wheels. Hence recalibration is sometimes necessary when changing wheel size on new cars.

Do modern cars still use the gearbox type speedos?

Edit: Thinking about that. Recalibration would probably be necessary anyway even if it was in the gearbox and you changed the wheel size. I remember in the old days you could unhook the speedo from the car when going on long trips. This obviously caused the odometer to stop working. My grandfather use to do it all the time LOL This wont work today because a faulty speedo will affect ABS.

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  # 995604 27-Feb-2014 16:30
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Klipspringer:
clevedon:

The speedo does not instantly stop if all four wheels lock. The speedo sensor is gear driven inside the gearbox and does not instantly stop working when all four wheels lock (as said earlier - very rare) , a vehicle has to have momentum for the ABS to work.

Unless you pick up a stationary vehicle with the wheels locked with your foot on the brake and throw it out onto ice and let it slide - yes the ABS will not work.


I realize we are off topic here so apologies. This is an interesting thread.

From my understanding the speedo gets its info from the wheels. Hence recalibration is sometimes necessary when changing wheel size on new cars.

Do modern cars still use the gearbox type speedos?

Edit: Thinking about that. Recalibration would probably be necessary anyway even if it was in the gearbox and you changed the wheel size. I remember in the old days you could unhook the speedo from the car when going on long trips. This obviously caused the odometer to stop working. My grandfather use to do it all the time LOL This wont work today because a faulty speedo will affect ABS.


Most late model vehicle have the speedo sensor in/on the gearbox and a lot of vehicle systems wont work if the speedo is not working or disconnected.

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  # 995608 27-Feb-2014 16:34
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jarledb:
Breaking under those conditions without ABS you will want to pump brake, which means you will have all wheels locked from time to time.


klipspringer:
This actually raises an interesting point.

So under these types of conditions, ABS actually takes this control away from the driver.

Or is it possible to "pump the break" on a vehicle with ABS when the ABS system has determined its better to not lock up the wheels?


So since locking your wheels on slippery conditions means you have no way of steering, and having learnt to drive with cars without ABS, it is as good as instinct for me to get off the brake to steer, even with ABS (given those kind of conditions). Which I see is not the recommended way (So a bad habit):

Cadence braking is the process of rhythmically applying and releasing the brakes in order to get a compromise between steering and braking performance. However this technique is only useful in cars without ABS fitted (ABS performs a similar process, but much faster and more accurately). If you need to emergency brake in modern vehicles, the best results are achieved by pressing the brake pedal firmly and keeping pressure on the pedal until you have come to a halt.

Source: http://www.drivingfast.net/road/winter-driving-myths.htm


I feel safer with the ABS brakes than I would without them. Especially for the circumstances where you have not been able to foresee what is about to happen.




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  # 995611 27-Feb-2014 16:37
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tdgeek: 
Traction Control is part of the VSA (Vehicle Stability Assist) system.

When one or both driving wheels has insufficient traction due to a combination of throttle opening, cornering force and low grip levels of the road surface, the Traction Control system will automatically reduce engine power until traction is re-established.


Traction control is another fun one for slippery conditions (snow/ice). Driving under those conditions you will notice the traction control and the ABS brakes a lot on really slippery roads.




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  # 995623 27-Feb-2014 16:55
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jarledb: Traction control is another fun one for slippery conditions (snow/ice). Driving under those conditions you will notice the traction control and the ABS breaks a lot on really slippery roads. 


Pedantic I know, but they are brakes - not breaks. 

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  # 995744 27-Feb-2014 19:16
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clevedon:
jarledb: Traction control is another fun one for slippery conditions (snow/ice). Driving under those conditions you will notice the traction control and the ABS breaks a lot on really slippery roads. 


Pedantic I know, but they are brakes - not breaks. 


Thank you, always appreciate opportunities to work on my english. Its not my first language :)






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  # 995753 27-Feb-2014 19:46
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it is amazing that a multilingual person can participate in an English forum. there are lots of people who only knows one language who can't spell :D (hint: not necessarily NZ)




Involuntary autocorrect in operation on mobile device. Apologies in advance.


1005 posts

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  # 995757 27-Feb-2014 19:59
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jarledb:
clevedon:
jarledb: Traction control is another fun one for slippery conditions (snow/ice). Driving under those conditions you will notice the traction control and the ABS breaks a lot on really slippery roads. 


Pedantic I know, but they are brakes - not breaks. 


Thank you, always appreciate opportunities to work on my english. Its not my first language :)


My apologies, I didn't realize.

I guess repairing cars, being my trade - seeing it spelt that way looks kind of wrong to me :)



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