RallyKeith Posted December 8, 2008 Share Posted December 8, 2008 A friend was in a fender bender saturday, due to icy road conditions, where the ABS did nothing. Now, he was driving a Hyundai SUV rental while his car was being worked on, but it begs the question if it would have mattered at all. So the question is, if at any speed, you SLAM on the brakes and get all 4 wheels to lock up instantly, like if you were on pure ice with racing slicks) what would the ABS do? Part of me says that it should do nothing, because at any given moment there is no difference in wheel speed between any of the wheels. Another part of me says the ABS computer should recognize a chage in wheel speed outside of the laws of physics and apply some function of ABS to all wheels. Thoughts? Experiances? Keith Link to comment Share on other sites More sharing options...
nipper Posted December 8, 2008 Share Posted December 8, 2008 ABS does nothiing on ice. Nothing does nothing on ice, short of studed snow tires. If all four wheels lock up the ABS has no reference speed. If road conditions are so bad that all four wheels locked up, the same would have happened with non ABS brakes. Have your freind leanr how to downshift the car to help slow down. nipper Link to comment Share on other sites More sharing options...
nipper Posted December 8, 2008 Share Posted December 8, 2008 Another part of me says the ABS computer should recognize a chage in wheel speed outside of the laws of physics and apply some function of ABS to all wheels. Its a simple computer, not the Starship enterprise nipper Link to comment Share on other sites More sharing options...
nipper Posted December 8, 2008 Share Posted December 8, 2008 It is very rare to get all four wheels to lock up, usually its just the front two. Ice is the one exception. Even in rain the rears usually have enough traction to keep spinning. Also slamming on the brakes is ill advised at any time. If he had to slam on his brakes he may have been driving too fast for the weather conditions (which is usually the case). Another question is what condition are his brake shoes and pads in, and what kind of tires he had on the car. The brake system is only as good as its weakest link. Most forget that the tires are a big part of that link. nipper Link to comment Share on other sites More sharing options...
rverdoold Posted December 8, 2008 Share Posted December 8, 2008 Downshift in time?!?! there is no time to realize that. Once wheels lock up its already to late to do anything else. I know it too well, kissed a tree, but ok airbags did not set off so thanks to seatbelts. Best tips i can give: Studded tires if you still wan to drive Stay home with nice warm tea Go by foot Link to comment Share on other sites More sharing options...
3eyedwagon Posted December 8, 2008 Share Posted December 8, 2008 The whole point of ABS is that it should never let the brakes fully "lock up". No matter how "hard" you slam on the pedal, the ABS systems seperates that action by using pressure bleedoffs, and proportioning valves. It uses magnetic rings and sensor to detect if a brake disc has come to a stop, meaning a "lock up". If it detects this, it releases the brake lightly, and increases pressure to other wheels. It "surges" line pressure to each caliper, creating a pulsation braking feel. If anything, a wheel should only skid for less than a second, and then return to "thresh hold" braking. So, if you were under your scenario: The wheels would only lock momentarily, and then the system would release pressure to the point they were no longer locked up, and continue to "thresh hold" brake until you were at a stop. All of this is supposedly happening far quicker than any of our brains can react. I think it's all BS. We need drivers with more training, and to stop relying on gadgets to save our ignorant lives. Sure, ABS helps a bit, but I'd rather be a talented driver without ABS than an idiot with it. Link to comment Share on other sites More sharing options...
nipper Posted December 8, 2008 Share Posted December 8, 2008 ABS has never claimed to help on ice. nipper Link to comment Share on other sites More sharing options...
RallyKeith Posted December 8, 2008 Author Share Posted December 8, 2008 Guys, do me a favor and try to stick to my question and not comment on the driving. As I said it was a rental hyundai so something like the brake pad condition is something he can't know, and can only assume was fine. Someone in the lane next to him and about 100 feet infront of him spun out and came into his lane. It was a snow squall on untreat roads that caused some very icy conditions. No time to downshift, no time to do anything but try to slow down and steer around, which is exactly what ABS is for, to allow you to steer around the accident. Link to comment Share on other sites More sharing options...
bheinen74 Posted December 8, 2008 Share Posted December 8, 2008 (edited) yep, on pure ice, even slightly on the brakes and all 4 will lock up and you will be off on a nice little slide. better just to downshift at the point and get the speed down. abs= mostly evil. if there is no time to downshift, just try to ease off the throttle and try to keep the car going straight, or around the obstical. Edited December 8, 2008 by bheinen74 Link to comment Share on other sites More sharing options...
Petersubaru Posted December 8, 2008 Share Posted December 8, 2008 I have compared 2 cars ..one with "snow tires" and the other with "all season"..when suddenly stopping with all season tires on snowy/slippery roads, the ABS was useless..as soon as you touch the pedal it activates the ABS ( like having your wheels lock-up and no control..might even cause your car to speed up if your on ice )..now the same model car with the blizzaks tire and when on the same road conditions, provided a much shorter stopping distance...my feeling is that the extra grip from the snow tires made the ABS worth having..but without snow tires to provide that extra "grip" it just might be better to disconnect the ABS for the winter...all the police cars around here have the ABS disconnected Link to comment Share on other sites More sharing options...
CNY_Dave Posted December 8, 2008 Share Posted December 8, 2008 Guys, do me a favor and try to stick to my question and not comment on the driving. As I said it was a rental hyundai so something like the brake pad condition is something he can't know, and can only assume was fine. Someone in the lane next to him and about 100 feet infront of him spun out and came into his lane. It was a snow squall on untreat roads that caused some very icy conditions. No time to downshift, no time to do anything but try to slow down and steer around, which is exactly what ABS is for, to allow you to steer around the accident. What *should* happen is the ABS would only allow a tiny bit of braking power to the wheels (that's what it is in the aggregate, on a small time scale its a lot of surging as mentioned earlier). On ice, I would expect: 1) (maybe) below some minimum threshold of traction, the ABS just can't cope and the 'minimum' amount it can apply the brakes is enough to lock 'em up (and once locked up, the ABS would indeed allow them to stay locked) 2) if its really slippery, brakes on or brakes off, there may not be enough traction for the front wheels to steer at all. and/or 3) On ice, with the ABS working exactly as its supposed to, there was so little braking traction available that the max braking effort the ABS could apply was basically bupkis, zip, zilch, nada. Dave Link to comment Share on other sites More sharing options...
bheinen74 Posted December 8, 2008 Share Posted December 8, 2008 I already posted, but I am sort of pissed off that these "technology" wonders in cars are forced onto us. Manufacturers charge the buyer in the long run, for all the tests costs etc involved, and yet again, it is stuff not needed. Just like airbags. If you wear your seatbelt correctly, airbags really do more harm than good. autoleveling headlights, really suck on the roads around here. et etc rant, and tires that monitor air pressure, what a waste. enuf said. sorry to ramble on other things Link to comment Share on other sites More sharing options...
RallyKeith Posted December 8, 2008 Author Share Posted December 8, 2008 I already posted, but I am sort of pissed off that these "technology" wonders in cars are forced onto us. Sorry if I came off whiney in my last post. My friend is a good driver and I don't want people attacking that. I just wanted to talk about this scenario with ABS. As for the technology being pushed onto consumers, a little over a year ago I was looking at the Toyota Yaris as a commuter car and I was plesantly surprised to find out that ABS was technically an option. Trying to find one without the ABS in the northeast however was a different story. Keith Link to comment Share on other sites More sharing options...
carfreak85 Posted December 9, 2008 Share Posted December 9, 2008 We need drivers with more training, and to stop relying on gadgets to save our ignorant lives. +1. Well put Sir. If all four lock up on ice, the ABS computer should momentarily release brake pressure to all four corners, then do the pulsing thing. But in the defense of the manufacturers, how much traction do you really have on sheet ice? Link to comment Share on other sites More sharing options...
Petersubaru Posted December 9, 2008 Share Posted December 9, 2008 +1. Well put Sir. If all four lock up on ice, the ABS computer should momentarily release brake pressure to all four corners, then do the pulsing thing. But in the defense of the manufacturers, how much traction do you really have on sheet ice? ...when suddenly braking on ice, the pulsating is happening so quickly that it feels like they are locked up...with more traction at the tire thread (for example useing snow tires) slows down this pulsating action Link to comment Share on other sites More sharing options...
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