Franko

ABS is designed to help you stop quicker on a slippery surface. So i wouldn't expect there to be much difference on a dry surface.

I would say its true that ABS helps you steer with greater controll under heavy breaking as ABS helps eliminate skid, but by eliminating skid i would expect the car to stop alot quicker too.

StickyMicky

i thought it was designed to help you steer while brakeing hard, not stop quicker

MJW

How ABS brakes work for anyone interested

Chris L

No it isn't. ABS is designed to let you keep control of your car. It allows you to steer and brake at the same time. It has nothing to do with improving you ability to stop on slippery surfaces. As John and others have rightly pointed out. On Ice and snow it can actually make your stopping distances longer.

This common misconception of ABS is its biggest hinderence. ABS is one of the greatest modern improvements to road safety. The problem is the lack of training and understanding of how to use it.

Chris

[Edited by Chris L - 12/19/2003 8:08:22 AM]

Allan

iTrader: (1)

Taken from MJW's link
Quote:
"Do anti-lock brakes really work?
Anti-lock brakes really do help you stop better. They prevent wheels from locking up and provide the shortest stopping distance on slippery surfaces"

It would appear "How Stuff Works" is wrong as well then.
Allan

johnfelstead

wouldn't be the first time.

Brit_in_Japan

I posted this on another thread. Interesting report on the benefits of ABS in winter conditions.

"For the more technically minded, below is a link to a report on the performance of different tyres on snow/slush, ice and rough ice. It also compares performance when ABS is ON/OFF. No tyre makes are mentioned unfortunately, but the performance of new studless winter tyres is impressive. Worn summer tyres, scary

Interestingly the findings show that on snow, stopping performance on average is better with ABS ON!

Report

"






[Edited by Brit_in_Japan - 12/19/2003 9:56:34 AM]

hurricane

However, not even someone as ****ing great as you in an STi5 can control the braking applied to all 4 wheels independently.

johnfelstead

I can do 2 at a time, whats your point?

Mick

iTrader: (1)

BIJ - interesting paper - thanks for the link!

Mick

hurricane

They clearly didn't test with a Subaru Impreza STi 5 RA.

Requin

I hate to get involved but I'm bored and have a stinging hangover, and also would like to know....

This is'nt true :
"Without getting too technical, the ability to stop depends on the co-efficient of friction between the tyre and road surface."


A huge amount of stopping power comes from the transference of energy to heat in the breaks,

So you have the greatest stopping power the moment before the wheel locks as you're transfering the maximum amount of friction /
heat to your breaks.

The friction between the tyres and the road can't get rid of the energy as fast as your breaks can.

Which is why if your breaks are boiling hot already they can't disipate any more energy so you get break fade.

Can someone correct me ? as I'd like to know for sure myself :-)

johnfelstead

They clearly didnt test a Subaru ABS system either. Have you done much driving on snow in an Impreza with ABS? Ever driven an STi5 Type RA with the diffs locked on snow?

MRK IV

lmsbman

Oh yes it does.We have been talking about emergency braking.So you are saying that it doesn't matter if you are driving on a sheet of ice or shell grip road surface!
The friction in the braking system is important when slowing down but once the brakes have locked its down to the friction between the tyre and road. I understand that there are occassions when the braking system isn't working correctly i.e. brake fade but the brakes then won't lock. You will stop, but in a much longer distance.

Franko

My (basic) understanding is,

When the brake is hit hard and the break pads lock the wheel the car will skid.

When it is skiding the only thing to stop it is the friction between the tyre and the road. (and wind etc etc) it is also difficult/impossible to have controll over the car in this situation.

With ABS,
When the car skids the ABS kicks in preventing the wheels from locking by switching the pressure from the brakes on and off so quick that maximum braking is applied without/minimal skid.
With this the car does not skid and can be controlled much better.

If there is virtually no skid then the car would surely stop much quicker than if there was skid?

It could be the opposite on a dry surface due to greater friction and the stoping forces could be greater than just the maximum pressure from the brakes.

However for a wet/slippery surface (given the way the ABS works described above is correct) the car would surely stop Much quicker?

After all when we hit our brakes hard on a road its with the intention to Stop (under controll) and thus ABS should/is designed for this?

What i understand is, the ABS helps keep controll of the car and stop much quicker under slippery conditions?

Sorry if i'm repeating stuff just cant get my head round how a skid on a slippery surface can stop the car quicker than maximum braking pressure applied by the ABS...

Chris L

It's not so much that you 'may' stop quicker, it's the common misconception that ABS systems are designed to improve your braking distances. It is nothing of the sort. ABS - Anti Lock Braking System - does just that - it stops the wheels locking. The point of this is to allow you to control the car and steer - something that isn't possible in a non-ABS car with the brakes locked on.

The problem is that it gives people a false sense of security. Drivers are less inclined to adjust their driving style because they think that electronic systems such as ABS will save them. Just as in the same way that some people think that putting on their fog lights somehow magically allows them to drive in thick fog at 90 mph in perfect safety

Don't fall into the trap of believing ABS will allow you to stop quicker - it doesn't. What it will allow you do is keep control of the car and avoid an impact - something which is totally different.

Chris

gossythevaleter

hence why when there is snow or ice on the roads i take my ABS fuse out

Steve Whitehorn

iTrader: (13)

I have always liked not to have ABS on cars. As I like to get a feel for when bakes lock up and where the threshold is. I feel I have more control this way. I also am a cadenance braking man. I brake or I steer.

From my own point of view I don't like drivers aids to get in the way of my control over a car.

ibmsman - You obviously have much more experience when it comes to specificaly testing ABS v non ABS cars. What do you think? Can a non ABS car be as effective as one with ABS with the right driver behind the wheel.

Or am I wrong/old school. I car with ABS is more effective even if it takes a bit of the control/feel away from the driver.

Best wishes
Steve

lmsbman

Steve

Hell of a hangover this morning, so sorry for late reply.

As I have said before, ABS is a brilliant bit of kit. However,I have only ever had to use it once in a real situation. It enabled me to avoid a car the just spun out of control in front of me on the motorway.

There is absolutely no way that you can replicate ABS by cadence braking. You just physically cant pump your foot up and down anywhere near as quick as ABS.

I can understand what you say about having the feel of a car. Hopefully, you don't lock your brakes every time you brake! Therefore, ABS should have no impact on your everyday driving. If you get the chance, go to a skid training centre. You will get taught how to use ABS properly and then no doubt you will see its benefits in an emergency situation.

johnfelstead

What steve is refering to is the feel you get through the pedal in a non ABS equipped car. You cant feel the brakes properly when you have all the ABS valves in the way between your foot and the pads. You also dont have the oportunity to use the brakes in the same way at the threshold of grip, where you may choose to ignore or even manipulate one of the wheels locking on corner entry for example. Cars with ABS loose a certain level of feel at the limits, the efect isnt just in a straight line under heavy braking.

mutant_matt

That's what I hate about ABS - the feel it robs from you!! There is a whole zone of delicate progression you can play about in on the limit of adhesion you just can't do with an ABS equipped car! Why someone can't produce a system will the feel and control of non-ABS but with ABS which will kick in when you really do need it (not like the Subaru ABS which thinks it's almost clairvoyant with it's early almost predictive cut in [img]images/smilies/mad.gif[/img] ). I suppose they could but the cost would be the problem on a production car.

BTW:Reply:IIRC, the RA doesn't have ABS so it would be tricky

Matt

Cabinet Enforcer

I've never been on a track, so have not had the chance to really play about with the brakes on my RS, but I have had a bit play with maximum braking force, and I have managed to induce a slight skid without the ABS kicking in at all, so good systems are possible, but since that was on dry tarmac it was a short lived experiance (and it nearly put my head through the screen).

The current generation of ABS systems can be tuned to the extent that they dont cut in until after a skid has started and then only feed in "abs'ness" gradually till the skid is reigned in. But most manufacturers seem happy to tune the systems so they cut in early and hard.