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MG MGF Technical - Anti lock brakes are crap
yesterday I once again had a moment with my anti lock brakes, when they withheld vital braking-pressure from me for a frighteningly long time after one of the front wheels momentarily lost traction on an undulation on a wet road. Not once in my life has anti-lock helped me escape from a dangerous situation but at least five times it has turned an absolutely harmless situation into a very frightening one.
Has anybody already tried to create an on/off switch for the anti-lock-system, maybe using one of the superfluos buttons on the dash?
I think I would have the car examined first then I would question your driving style.
|You shouldn't get into a situation where the anti-lock breaking system comes into operation!|
|The anti-lock can be disabled by removing the fuse located under the front bonnet. No reason to suppose that an isolator circuit could be installed.|
Why do you regard the ABS in such low esteem Nikolaj?
|Its been a godsend to me in the last year, on at least two occasions it has brought me to a halt in emergency situations whilst cornering.|
glad to say neither situation was of my making too.
|Could your tyres be to blame? When I first bought the F, it had some crap tyres on the front. I could make the ABS come on very easily. As I recall, it happened once when braking for a stop light and the front tyres went over some ruts which were full of water. Having also had some scary aquaplanning experiences I decided to change the tyres for some decent ones - hey presto, solved.|
|David Lamas Loureiro|
|I would say that David was probably spot on in his observations with regard to tyres. Braking with Bridgestone tyres (before upgrading to green stuff brake pads) was far superior to braking with NCT-3 tyres.|
I reckon you should consider changing your tyres before dissabling the ABS Nikolaj.
|If the ABS is not releasing the locking wheel, then maybe it's the brake caliper that's causing the problem. Of course, if you have decent tyres on the front, as well as good brakes, then ABS wont be involved nearly so often.|
|Maybe I should give you a more detailed picture of the situation: Where I live they use small metall studs to mark out the lanes in town. As everybody knows whet metal isn't very grippy and my too-low-ride-height (335mm but I 'll get it sorted next week) doing the rest, one of the tires must have lost grip under absolutely normal (I swear!!) breaking. The same happened to me once in Italy on a metal expansion-joint (?) on a bridge and with a Porsche in a very sharp corner where the inner front wheel of such a stiffly set up rear engined car is prone to lose ground contact when driven quickly (a Golf does it with the inner rear wheel!). |
Also in soft snow anti-lock is a real disadvantage (locking up the wheels would be much more effective!) , so in the region of Germany where I come from going downhill with anti-lock can be a real nightmare.
Don't get me wrong, the system is a very good thing in theory and most circumstances but in situations as described above, when a wheel loses traction for a split second, the system is too keen to take away too much brake pressure for too long a period of time, and that's what I dislike. That's all.
|hey Nikolaj, you should talk to the two ladies who work in the bar where I'm a DJ (no, not a red light district bar, in fact a British bar in downtown Luxembourg, drinks only!). Yesterday it rained here in Luxembourg after it didn't for the whole day, and so the roads were very slippery (saw 2 accidents in 5 minutes!). They had to brake for a passing car, wheels locked and car slid straight towards a truck next to them 'because I tried to turn the steering wheel but the car just kept on sliding towards the truck'. Kaboom! Truck torpedoed car afterwards rearwards into barrier, reducing the length with at least 2 feet. Car looks now a bit 'different'... ;-) but the (nice) girls are luckily unharmed, one has just some pain in her back (speed was not too high, around 50mph).|
If they had ABS their car would have a better chance still being intact...
I almost crashed my car into a concrete pole in Dover once, but ABS and some tricky steering manoeuvre saved my F. I love ABS!
The ABS is an anti-lock brake system it is not a traction control.
If the ABS is switching the brakes off and on when the wheel locks up on a slippery surface THAT IS GOOD that is what it is supposed to do. I have ABS on my bike and it saved me from coming a cropper on a diesel patch the other day and THAT IS BRILLIANT as not long ago on a non-ABS bike a patch of diesel sent me down the road.
Whatever the surface, metal, oil, ice etc it is better to keep control with the wheels rotating than no control with the wheels locked up.
The thing to remember is if you are on such slippery surfaces then avoid braking as much as possible.
Also remember that ABS is an aid to good driving not an answer to bad driving.
|Snow on roads is not so much of a problem here in the UK, but I have heard that ABS can actually increase braking distances on both loose surfaces and snow. So I guess that if you were living in a region that got a lot of snow, having the option to switch off the ABS could be very useful.|
In this case, you will need a 70 amp relay (costs about 5 GBP from Maplins) to isolate the ABS on command from a switch in the cockpit. Having similar thoughts to build a circuit to isolate the EPAS- but that is another story!
|Thanks for all the useful comments (especially Rob's), sorry to those who now think of me as an irresponsible idiot :(|
Probably I was a bit too provocative when starting the thread. In order to hopefully sort out all the misunderstandings: I am only concerned about the anti-lock kicking in on a very small patch of low-friction surface and then being lethargic at reinstalling full brake pressure although enough grip is available. Sensible driving should be the basis for all our discussions, it should go without saying, shouldn't it?
P.S. Rob, I have followed the thread about the EPAS and I like the idea of manipulating it the way you plan very much!
|The reason that ABS can increase the braking distance in snow is because locking the wheels causes a 'snow drift' to build up in front of the wheels, forming a barrier to forward movement. ABS just rides over the top of the snow.|
|The other thing to remember is that if the wheel leaves the ground it will lock at that time, when it hits the ground it mightstay locked depite no increase in breaking pressure, due to the fact that a slidding wheel has a lot less firction than a rotating one. so its imposible to say if the ABS is helping or without it you would have locked that wheel and it stayed lock. |
mind you i wasn't there, so i don't really know do i.
personally i love the ABS and i have got myself into trouble to many times when the ABS has saved me. the abaility to steer is great and it stops well.
|Nikolaj wrote: "... the anti-lock ... being lethargic at reinstalling full brake pressure although enough grip is available."|
YES! I think that's exactly the point! That's the reason why I would rate the anti-lock system of the F 'not perfect'. I fully agree with all the statements from above, but I also can't believe that there is nobody else (except for Nikolaj) who ever mentioned that lethargic behavior of the anti-lock when it comes to reinstall full brake power.
From my point of view I would say the anti-lock works great under most circumstances - except for snowy roads - and we have plenty of them here in Austria (sorry for being from Austria at the moment), so I want to express I have some experience with anti-lock braking. But there are some 'normal' braking situations that become dangerous DUE TO THE ANTI-LOCK because the anti-lock does not stop working (vibrating) fast enough. I can't recall what the common charateristic of these situations is. I think it was always at low speed (not more than city speed), and of course the road surface was dry and clean (after the road section that caused the anti-lock starting).
|I had always believed that the biggest plus of ABS was the fact that you when you slam on the brakes as an instictive response - it gives you the ability to be able to steer away/around the obstacle.|
eg child or animal runs into the road
This used to be demonstrated on MG test days by having a huge inflatable HGV truck, you raced up to it at high speed, the driver then slammed on the brakes and steered safely around it at the last moment.
I had switchable ABS on an Audi once, it was 'for use in deep snow' has been mentioned
|>ABS? Luxury..... |
Todays luxury is tomorrows essential!
showing my age eg:-
When I first started motoring it was sheer luxury to have:-
A windscreen washer
Wing or door mirrors
And things unheard of in cars:-
Power Assisted Steering
Fuel injection for petrol engines
And as for computer controls - the first commercial computer I ever saw took up the whole of one floor of the J.Lyons (a name from the past) Cadby Hall Building and had as much power as a pocket calculator of today.
Now where on earth did I leave my Zimmer
|Thanks, Markus, for your supporting comments! I'm glad I'm not the only one...|
What I now plan to do is to go onto an empty parking lot and try to simulate the situation in which I think ABS can be dangerous. I will then measure breaking distances with and without ABS. Then we will have some foundation for our arguments!
Nikolaj (who agrees with Markus that ABS works great under most circumstances BUT...)
as promised I went to a big parking lot with a wet but very grippy surface today. After a few test runs I did the following:
measured the braking distances from 40km/h with and without ABS both of which repeatedly came out as 7m.
Then I collected a few small branches put them together in a way that I would run over them with my right front tyre about 2 meters after initiating the braking-manouvre.
The braking distance without ABS was still absolutely the same : 7m.
Then I reengaged the anti-lock system and what then happened was just what I had expected: The ABS took away a lot of the braking pressure as I ran over the branches and didn't give it back quickly enough. As a result I didn't manage to stop the car earlier than after 10m!!!
Neglecting the 2 meters in front of the branches this works out as a frightening 60% increase in braking distance!!! Overall it's still an increase of nearly 43%!!!
This means that if in town someone had stepped out in front of my car and there had been a branch or one of those metall studs on the road I would have hit him with about 12 km/h at a point where I would have already stood still without ABS! Makes you think, doesn't it?!
|Nice one Nikolaj- a very interesting result from your test. It puts the reputation of ABS on shakey ground. This is something that needs to be repeated a few times. Would an ABS supporter like to reproduce this test and confirm or attempt to refute the result?|
When going over the branches, did you find the right hand wheel locking up, or notice any change of direction?
Rob (whose car does not have ABS)
|If you disable ABS, does 'cadence' braking work OK ?|
EG if you rapidly brake and release, brake and release etc - do the brakes release properly ?
I would not regard this as an ABS problem - rather as a brake problem that shows itself when ABS operates.
(I like the test with the branches ... )
no, neither with or without the ABS did I encounter a change of direction, probably because the branches did only interfere with the braking manouvre very, very briefly. The wheels locked up completely without ABS (my poor tires :( ), but then again even stepping of the brakes, steering around a virtual object and still coming to a halt within the 10 metres of the ABS would have been possible.
Important is that I am not talking about high speeds here and I , too, feel better with the ABS engaged when driving at high speeds, but at speeds relevant to city driving I think ABS, and especially that of our MG-F, is highly questionable.
Greetings from cold and wet Germany,
|I have done one or two ABS tests myself.|
One test using a BMW vehicle not my own involved a gravel track, slam on the brakes first with ABS and then without ABS. With ABS a nice controlled stop in a distance of about 30 yards. Whithout ABS I stopped in a shorter distance, but the motor bike went on for another 10 yards.
|Maybe the MGF2001 could incorporate something that does the opposite to the EPAS: doesn't engage until you're doing 40+MPH?|
One of the road junctions I stop at on the way home has a shart drop (misalignment of concrete surface) just before the line. My ABS cuts in regularly there, and I think you're right - it means I take longer to stop than if the ABS hadn't cut in.
I don't think anyone has ever claimed that ABS stops you more quickly.
I does stop you locking up and loosing steering control.
For your average punter they are much more likely to stamp on the brakes
and loose all directional control. In this case, ABS allows them to avoid danger.
The downside is that they can sometimes take longer to stop.
Dangerous ? yes, but less so than loosing steering
Compromise ? yes, but I'd prefer to steer.
Am I for ABS ? yes
I have ABS and would now never buy a car without it.
|A good test IMO would be to drive at a constant 30mph over a loose gravel surface under the following conditions.|
1. ABS enabled - stand on the brake pedal. Normal practice for stopping an ABS equiped car in an emergency.
2. No ABS - stand on the brake pedal. Common reaction by a majority of drivers in an emergency.
3. No ABS - Manually pump the brake pedal. A known method of preventing the wheels totally loosing traction, ie. should be quicker at stopping the car than skidding to a halt as in 2 above - also retains driver control. And, yes this is what ABS is supposed to do for you because it's not that easy to do in the real world.
All three tests should be repeated in both a straight line and during cornering IMO. Ideally a number of different surfaces should be experimented with. ie. dry road, wet, muddy, gravel (as above), leaves, ice. I think in most cases you'll find most drivers would stop quicker with an ABS equiped car.
Home of the F'ers Gallery and MG Dealer Guide. :)
|Some interesting posts. To date I've been fairly satisfied with the ABS on my F. Too some degree,I do have to agree with Nikolaj that there seem to be situations where the ABS will engage and NOT disengage quickly enough and prolong a stop. (but as Paul said, at the benefit of maintain steering control)|
I think Nikolaj's test is fairly realistic that the F's ABS catches the initial slip (running over the branches), engages, but doesn't disengage once back on normal surface (or as quickly as we would expect). Out of curiousity, is there a minimum time period that an ABS will engage, 1 sec? 1/2 sec?
PS Ted -great bike ABS test!!! LOL (hope you and the bike were OK..)
|Forgot to mention, I have yet to have the ABS engage ever since I upgraded to Bridgestones all round. NCT3's seem to provoke the ABS more.|
Tokyo got hit by a typhoon last nite and the Bridgestones were amazing in their wet traction. Perfect hydroplaning conditions - torrential rains, roads flooding... Not once did I feel the tires slip or ABS engage! Saw a number of cars in front doing a little hydroplaning dance...
I think you've heard this ad naseum on this board, but if you've got the budget, upgrade your tires! Get rid of those NCT3's. Adds to the grin factor and you'll sleep better knowing they'll stop your F better.
|I've had the ABS come in with my S02's, but only in criticak moment on a bend, so boy was i thankful i wasn't locked up. I was pushing it though.|
interesting tests. is it ABS in general or MGF abs do we think. and it would be interesting to see if any big test centres do similar tests and have any results fromwell controlled tests.
|The abs system looks at the relative speeds of all the wheels and if one is rotating significantly slower than the others the abs computer interprets this as a lock-up and backs the brake pressure to that wheel off (I remember 7 times a second?) (traction control does the opposite - applies the brakes on a spinning wheel and/or backs the throttle off)|
As mentioned the idea is that an average driver on a normal surface will be in trouble if a wheel is locking. Abs leaves him/her in control. In theory if all 4 wheels lock at the same time (after a jump?) the abs will not detect any speed difference between the wheels and will not engage.
So it's not surprising that the car takes longer to stop if the abs engages - you're using less stopping power and so will take longer to stop. The upside is that you maintain directional control and you can feel that one tyre is at the limit. Also you won't flat-spot your tyres!
I wouldn't be without it. Has anyone also noticed that heavy braking approaching, say, a roundabout in the wet causes the abs on the rear wheels to engage? You can feel a little 'squiggle'. Worthwhile not to have the pink-panther effect - rear wheels passing you as you go onto the roundabout!
This thread was discussed between 05/07/2000 and 10/07/2000
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