Effect of ABS on Dry Pavement Stopping Distance

Messages
4,844
Location
Saskatchewan
Last weekend I was the passenger in my buddy's '04 Cummins when he had to make a somewhat-quick stop for a red light. It really wasn't that hard of a stop, but he mentioned right after that it feels kind of funny when the ABS kicks in on the back wheels. I was surprised that ABS needed to activate for that particular stop, so we headed to a clean pavement area for some braking tests. As expected, the truck's braking was less than impressive. But what we didn't expect was that the truck seemed to stop better under threshold braking - in this case keeping the ABS from activating - than it did on a full ABS stop. So we got my Mazda3 and, while the braking was much better, it still seemed to stop better without the ABS activating. I know that you can stop better without ABS on dirt and snow, but isn't ABS supposed to reduce stopping distance on dry pavement? Has anyone else tried this?
 
Messages
2,837
Location
MO
Ignoring the benefits that are supposed to occur by having ABS on icy/wet/snowy surfaces I belief the big benefit is the abilty to maintain steering control when the brakes are fully applied in a panic/emergency situation. Supposedly, when the front brakes are locked and the tire is skidding little to no steering can occur. ABS allows a "pulsed" stop that allows steering control.... thus, braking power combined with the ability to steer around an onject, etc.
 
Messages
866
Location
Norway
When the front brakes are locked and the tire is skidding, there is LESS friction compared to a tire that is braked close to skidding. The ABS system will pulsate around that point. A experienced driver can "find" the close to skidding point and do a better job than the ABS system. This is on dry pavement.
 
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23,591
quote:
The ABS system will pulsate around that point. A experienced driver can "find" the close to skidding point and do a better job than the ABS system. This is on dry pavement.
I'd substitute "experienced" with "skilled," but I agree. Alas, only a smll percentage of drivers ever get to try out their vehicle and their own abilities on the track and even fewer take driving courses that teach how to handle a vehicle in extreme situations. The average driver is certainly better off with "stomp on it and steer," which ABS allows. Sadly, some drivers get scared when the ABS begins doing its job and get off the brake! Driver education is generally inadequate. ABS is of advantage to everyone on partially slippery/dry surfaces. You'd need four brake pedals and four legs, one for each wheel, to compete with ABS! I'm not a fan of ABS on completely slippery surfaces like ice and certain types of snow. It can be like having no brakes at all. Locking wheels skillfully lets you turn your car if you know what you're doing. On a car with ABS you're stuck with the handbrake. If you have to rely on a foot-activated e-brake, you're dead.
 
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7,077
Location
Ontario, Canada
If the braking system had a way to know the car's road speed, brakes could be modulated to just at the threshold, without ever skidding or pulsating. This would require a unbraked 5th wheel, maybe an accelerometer and pitch/yaw measurement, or some kind of camera watching the ground under the car. I really wish I had an ABS on/off switch for winter driving. I do a lot of driving in heavy snow, and ABS doubles the braking distance.
 
Messages
1,251
Location
Austin, TX
quote:
Originally posted by oilyriser: If the braking system had a way to know the car's road speed, brakes could be modulated to just at the threshold, without ever skidding or pulsating. This would require a unbraked 5th wheel, maybe an accelerometer and pitch/yaw measurement, or some kind of camera watching the ground under the car.
How about something like the optical mouse that scans the movement?
 
Messages
950
Location
Loveland, Ohio
I also think there is a big difference in ABS systems in how effective they are, and if you have 4 wheel disc or disc/drum combos. Some simply work better than others. There have been tests done by Consumer Reports and also by some of the automotive mags, and it is difficult to make generalizations. I used to think that ABS was a big advantage, now I think it depends on many different factors. Sometimes I think it is a case of you get what you pay for, and when GM can find a way to make them standard on a Cavalier, look out. They found a way to keep the cost down and they probably don't work as well as the more expensive ones.........
 
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1,983
Location
New Brunswick
I suppose ABS quality depends on if it's a 2 channel or 4 channel ABS system. 2 channel being both wheels on one particular axle are controlled together, and 4 channel ABS each wheel is controlled individually.
 
Messages
866
Location
Norway
quote:
Originally posted by moribundman: I'd substitute "experienced" with "skilled," but I agree.
That's what I tried to write [Smile] Engish is my 2. or maybe 3. language...
 
Messages
4,378
Location
Camas, WA
I think that initially the Dodges only ABS on the front, either due to cost or because die hard off roaders like being able to lock up the wheels for plowing thru some types of surfaces. People then complained that the rear locked up easily and broke loose, which is a problem with pickups anyway, so they added ABS to all wheels. In a pickup with no load, especially on the diesels, I'd expect the ABS to kick on early as the rear is so light. I have a Dodge diesel with ABS on all wheels and find that it works well as keeping the truck straight under maximum braking. A friend with one tied his out on a ice covered hill in the Bay area a year or so ago, and he said that it blinked at him all the way down the hill and as he zipped past the stop sign, but he stayed straight :^)
 
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36,461
Location
ME
Most family car type vehicles heavily bias the brakes towards the front so if they lock up the car will plow straight ahead and keep the driver out of trouble. With 4-wheel ABS they can (if they want to) more equally proportion things for better handling under moderate braking.
 
Messages
1,686
Location
VA
I have an '02 shortbox Silverado, and braking distance on dry pavement still seems weird. But then, all I can compare it to is that powerless feeling of trying to steer a car with one or more wheels locked and tires squealing. (Anybody ever drive a Duster with drums all around?) The ABS on this truck will kick in with the slightest braking on bumps like RR crossings or washboard dirt roads--that's a pain. obbop's comment--steering control under full braking--is right on. I was driving through Wyoming's Big Horn Basin one night. I knew the road well but kept glancing over at a fire burning on the Pryor Mountains. Suddenly a red calf was in the middle of my lane. I stood on the brake pedal at 65-70 mph and steered right around him. There wasn't even a chance to think about it until it was over. ABS saved my truck and that calf for sure, and possibly me as well. The year before, I was driving an '87 Caprice cop car in the same area, at night. A deer jumped out in front of me. It just barely escaped, but I put a flat spot on one tire and had to work to keep the car on the road.
 
Messages
3,593
Location
Outside smalltown, IL
quote:
Originally posted by oilyriser: If the braking system had a way to know the car's road speed, brakes could be modulated to just at the threshold, without ever skidding or pulsating. This would require a unbraked 5th wheel, maybe an accelerometer and pitch/yaw measurement, or some kind of camera watching the ground under the car. I really wish I had an ABS on/off switch for winter driving. I do a lot of driving in heavy snow, and ABS doubles the braking distance.
The mechanism would also need to know the friction coefficient of the pavement, the type of tires and amount of wear on them, vehicle load, etc. Not so easy to do. I've been underwhelmed with the ABS on my 4Runner in the winter too. I guess it's ok if you're not paying attention and just want to mash the pedal...
 

rpn453

Thread starter
Messages
4,844
Location
Saskatchewan
quote:
Originally posted by oilyriser: I really wish I had an ABS on/off switch for winter driving. I do a lot of driving in heavy snow, and ABS doubles the braking distance.
That's exactly what I was thinking last winter, with Goodyear RS-A's on my first car ever with ABS. I pulled the ABS fuse and it lit up the whole dash though. I probably would have eventually rigged up such a switch, but a week later, my steelies and studded tires came in and it wasn't an issue; the ABS came on maybe 2 more times the rest of the winter, and just lightly. So now I finally have a situation in which I want ABS, since it will make my studs last longer! A switch would still be nice to have for deep snow days, but not worth the effort.
 
Messages
260
Location
York, PA
quote:
Originally posted by 55: I suppose ABS quality depends on if it's a 2 channel or 4 channel ABS system. 2 channel being both wheels on one particular axle are controlled together, and 4 channel ABS each wheel is controlled individually.
I guess that makes mine a 3-channel? Each fron wheel is controlled separately and both rears are controlled together. I actually like mine in the fall/winter as it has actually saved my a** on wet leaves and icey patches on hills, and even in a couple iced-up intersections where I slid at the first touch of the brake pedal. After 6 yrs I am finally getting used to how they work, I just wish my particular car used a better system as the solenoids leak and the pump runs all the time when I have the relay installed. I've never actually been able to activate them on dry pavement, though. I have locked the tires up in panic stops (got cut off) with the system disabled but I haven't actually noticed any difference in braking, except for pedal feel - The ABS makes the pedal feel softer.
 
Messages
8,711
Location
Nothern USA
You can keep you Bosch systems requiring the expensive maintance. I will stick to my GM systems. Ran the ABS on my 92 Grand AM, early in the model year, first year as standard equipment, 10 years without a fluid change or any ABS problems. Have almost 4 years on my Cavalier now, same thing. When it comes to reliable quality at low cost, nobody matches GM's engineering. Experince means nothing if you are still making the same mistakes the last 40 years. I will gladly give up a little dry road stopping distance for the control I gain in the wet and ice.
 
Messages
2,698
Location
Silicon Valley
quote:
Originally posted by labman: When it comes to reliable quality at low cost, nobody matches GM's engineering.
Why would you want to bait us like that?
 
Messages
8,711
Location
Nothern USA
Was it BMW or Mercedes Benz that brought the masses the self starter, automatic transmission, floating caliper disk brakes, electronic ignition, EFI, computer control, ABS, and easy to service cartridge filters? My Cavalier has all of them except the automatic transmission. Instead it has a Getrag I have far more trouble sorting out 4'th and reverse than I did in my Grand Am with the made in Muncie 5 speed. I don't think great engineering means expensive, complicated, maintenance intensive cars.
 
Messages
12,385
Location
Northern CA
quote:
Originally posted by labman: Experince means nothing if you are still making the same mistakes the last 40 years. I will gladly give up a little dry road stopping distance for the control I gain in the wet and ice.
That's called 1 years experiance 40 times, not 40 years experiance. [Big Grin] I had some problems with ABS at first. After a fair amount of drivng on the edge of limits over the years I had developed an danm good braking ability. The feed back for the ABS working told my reptilian brain stem that I was losing traction so I would back off the brakes. That's bad when it's the rear ABS on a lightly loaded pickup that's sending the message. [Eek!] It's also not particularly good to switch between vehicles with and without ABS. Now that I no longer have my non-ABS motorcysle, and all 3 four wheeled vehicle have ABS, I have no problem with it.
 
Messages
345
Location
Northern California
I think perception also plays a part in evaluating ABS performance. I know when I brake a normal or ABS system the more I push down the more I expect it to slow down. When the ABS activates the rate of slowing down doesn't keep getting more in spite of more pushing down so it feel like the vechicle is speeding up when it is not. Simularly when I brake on ice and the vechicle starts sliding it feels like it is accelerating; just because it is not slowing down any faster like I am expecting (or hopeing). I would tend to believe the objective measured tests and not my expectation ladened perceptions. From what I have read except for soft dirt and snow which can be build up in front of the locked wheel, ABS systems stop fastest, eer slowest, oh whatever.
 
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