ABS

[Danny06]

Ok i took my 88 sport up for mot the other day and they failed me as the abs aint workin?? wot could be the problem?

Also wot could be wrong that she is hard till start? she is runnin with a hight lift cam and ported n polished gas flowed head that make any diff??

Any 1 recomd any good bmw garges or people who work at e30's in N.Ireland??

[Brianmoooore]

IF you give us some kind of clue as to what the symtoms are with the ABS, then we may be able to offer some help!
Does N. Ireland use the same MOT regs as the rest of the UK? ABS doesn't have to work for the MOT test, or rather it won't be tested, as a road test would be required to determine that it's not working.
All that has to work is the ABS warning light, which has to come on with the ignition and go out when the engine starts. JUST LIKE THE OIL PRESSURE LIGHT.

[Danny06]

IF you give us some kind of clue as to what the symtoms are with the ABS, then we may be able to offer some help!
Does N. Ireland use the same MOT regs as the rest of the UK? ABS doesn't have to work for the MOT test, or rather it won't be tested, as a road test would be required to determine that it's not working.
All that has to work is the ABS warning light, which has to come on with the ignition and go out when the engine starts. JUST LIKE THE OIL PRESSURE LIGHT.

Funny u should say that as i had the car up 4a retest as failed on the abs warning light not workin so i got it fixed up, fink it woz a bluff job tho lol, but wen took it for the retest the mot man took it out 4a road test n failed me, n said that my abs wozn working at all and the light woz just wired up!!

[junkmonkey]

Hi there,im in the same boat...ive got a 1984 323i from Germany and my abs lights on all the time,my abs sensors(or perhaps one of them needs cleaning up or replacing but feel abs is for bad drivers and would like to uprate the brakes therefore if possible remove the abs altogether....does anyone know if this can be done?

[anton]

hi there.

the abs simply has a pump, which simply PUMPS the breaks so they dont lock up, this is wired via a relay to your sensors, your warning light etc... so removing abs is basically, removing the wiring to the warning light, the ABS relay and unbolting the sensors from the front struts.

and simply pulling it out.

the rest of your brakes work on hydraulics via master cylinder so this wont be affected, i think the brake lines might make a Y split to your brake calipers and your sensor units on the struts, so you might need 2 new front brake lines.

all in all i dont think this is a difficult job, take it to a good auto electician and he should be able to do it, the mechanical work involved is VERY minimal, 4 - 6 bolts in total more or less.

its mostly removing the wiring and "sensing system".

thats all

good luck

Anton

[Brianmoooore]

i but feel abs is for bad drivers

Like to know how you can apply more braking force to one front wheel than the other when the front wheels are on different surfaces like ABS can.
Removing it could lead to some very interesting correspondence between you and your insurance company (or the local coroner) one day.

[DanThe]

Dont remove it, its a lot easier to repair.
My car didnt have ABS as standard so I took the system from another car and fitted it into mine. Simple really

[anton]

howsit

danthe is right. easy to repair. as to how it does more braking on one wheel than the other, ABS is not to be confused with EBD (guys correct me if im wrong) EBD is electronic braking distribution, this can distribute brakeing power to the wheels that have more traction. you'll often if not always find that vehicle with EBD also have traction control, i think they share certain electronic systems..

you could bullshit the mot guys, simply UNPLUG the ABS relay(this is how they disable your abs system when going to advanced driving courses)

now your abs light might shine. next you simply remove the wire that light the abs light... or install a simple on off switch inline to the abs light wire..

but simpler to rather repair your abs.

cheers
Anton

[Danny06]

Just wonderin if i hade the abs warning lighjt wired up so that it comes on with the oil light would she pass mot????
Car has till go back for a full test again!!

[anton]

abs systems are actually quite straightforward, it is simply a hydraulic system that pulsates the brakes, to mimic the action of one PUMPING the brakes, it limited traction situations. IT DOES NOT DISTRIBUTE BRAKING FORCES.. EBD does that. ABS merely "switches" your brakes on and off so to speak a few times a second.

in fact, back me up here guys, sometimes with abs it actually feels if your car doesnt brake aswell as with non-abs.
but with non abs u run the risk of locking up your brakes.

but honestly, its not THAT easy to lock up your brakes.

to fix abs on an 17/18yr old car isnt expensive. just goto a reputable place to sort it out for you,., will be cheaper and less time than an auto lectrician tinkering your wiring to bullshit the mot people.

man drives down wet road at 100mph, man needs to stop and in a hurry, man cant skid or risk crashing into several cars, man has to pump the brakes, that means u simply press and depress the brakes several times etc..
your brakes wont lock up and you will stop. this is EXACTLY like what abs does for you. except with abs, u simply HAMMER the brake pedal and the car does every FOR you.

the pumping action gets done by hydraulics and electric relay instead of your foot. thats all.

cheers
Anton

[jaistanley]

That really isn't how abs works.

Road speed sensors detect the rate of decceleration of each wheel. Solenoids in the 'pump' are opened releasing pressure in a caliper deemed about to lock up. This drop in pressure prevents the hydraluic pressure from the master cylinder pressing the pads on the disks so hard, reducing the rate of decceleration of that wheel. It samples it many times a second and flips the solenoid on and off giving the gravel like felling you get.

Simply pumping your brakes does nothing. If you have disk run-out an initial quick dab of the brakes before you apply them takes the space between your pads and disks away so the travel of the pedal is all applying pressure, thus making the brakes easier to control. Good practice when braking is a very quick and gentle dab of the brakes before increasing pressure in a rising fasion. As any wheel is felt slipping, pedal pressure can be reduced slightly. The remaining wheels are also dealt less pressure but this usually allows the slipping wheel to catch up and pedal pressure to be re-applied.

Jai

[anton]

hi there,
abs however isnt the ultimate in braking... its an automated braking assist... but pumping the brakes can to a degree prevent lockup... which is in essence what abs is designed to do..

here is a technical explanation:

How ABS works


ABS systems use a combination of electronic and hydraulic systems to modulate the brakes individually to prevent them from locking. Antilock systems basically consist of wheelspeed sensors, a hydraulic control unit (HCU), and an electronic control unit (ECU).

During braking the wheelspeed sensors measure the rotational speed of the wheels and forward this information to the ECU. If the ECU determines that one wheel is decelerating at a much greater rate than another (indicating that the brake is about to lock), the ECU directs solenoid valves in the HCU to open to release hydraulic pressure to the brake until the rotational speed of the errant wheel matches the others.

Because of the complexity of the system, when the engine is started, a self-test sequence occurs. If the check is successful, the ANTILOCK and BRAKE lights will extinguish. If some component fails to check out, one or both lights will remain lit. One or both warning lights may also come on while driving, also indicating a problem. If just the ANTILOCK warning light comes on, some ABS component has failed, but the car still has power-assisted brakes. If both the ANTILOCK and BRAKE lights come on, the car is without power-assisted brakes, which is very dangerous. If just the BRAKE warning light comes on, this may be caused by low brake fluid or worn brake pads.


cheers
Anton

[Brianmoooore]

Four different brake related warning lights on an E30. Brake hydraulics and pad wear are different lights.

[Turbo-Brown]

I too was of the impression that elderly ABS systems dole out the same pulsing to all corners, regardless of which wheel's about to lock up.

I'm also about 99.9% sure that it is possible to stop quicker on a dry surface without ABS than on a wet surface if you're a skilled driver (which I'm not but I know the principal) and can keep the wheels on the verge of locking up and slipping over the surface of the road at up to 15%.

Inevitably though, none of us are as skilled as we'd like to think, and in a panic situation we will all just stamp on the brake pedal which is why ABS is generally heralded as a good thing.

However, it doesn't necessarily reduce stopping distances under all circumstances. I had an arguement with a guy in the office a few years back in which he stated that the 30mph speed limit was no longer valid as it was set decades ago and that ABS and modern brakes meant he could stop faster now and as such it was safe to speed in 30mph zones.

I did some digging though AutoCar road test reports to find some typical values for the 30-0 brake test and found that, despite improvements in brake technology, the 30-0 stopping distance has remained at around 30feet! Although stopping distances from higher speeds had reduced dramatically.

Surprisingly few people would have guessed that a Triumph Herald and a Lambo Murchie-whatsit will stop within 12" of each other after a panic brake from 30mph!

Now there was a pointless rant!

DON'T SPEED IN 30MPH ZONES!

[jaistanley]

I agree that ABS isn't the ultimate.

To my MK2 golf I fitted 280mm cross drilled disks, Vr6 calipers, 23mm master cylinder, braided hoses and a small servo. All this was in aid of adding driver feedback and feel. People used to get into it and nearly crash into the first car becasue the pedal was so hard! They'd complain the brakes were shot. They were actually monsters, I could seriously outbrake most cars on the road because I could feel exactly when the wheels were going to lock up and lift off a little. I pretty much never

ABS is very good for those panic moments though. How many of us have the presence of mind to gently apply the brakes and watch for slip when a 5 year old has jumped into a rain soaked high street??

I also agree dont speed in 30 zones.

Early ABS may well have applied the solenoid to all wheels, not ideal by any means so I imagine it was on very basic 3 channel systems.

I modelled an ABS and stability programme in ADAMS whilst at Uni (I have Beng in Automotive Engineering) and doing a project at Dunton Ford; using wheels speed, coef of friction, dynamic suspension charachteristics etc. Conclusion being that (basically) systems are set to 'soft' and generate less absolute grip in good conditions but due to speed of response are better in moderately bad conditions. More performance orientated systems (re-valved to release less pressure and programmed not to kick in too soon) can be better in the dry but sacrifice a little wet performance.

Jai

[anton]

jaistanley,

could u tell me what ebd is? the above when i mentioned it was actually educated guestimate....

u seem to b quite clued up on these things..

cheers
anton