Anti-Lock Brakes

Page 1 of 5  
Anti-lock brakes...and that's ABS...work mostly in the rain or snow. On dry pavement and with the wheels straight...a car will most often make a emergency stop without any wheel lock-up...and that's due to
electronic-brake-balance along with modern tires.
But check out your anti-lock brakes with a drag-test to make sure they are not costing you. Drive by a sign on the Interstate at 70 MPH, then let the car coast down to 40 MPH, and note the distance the car coasted. Now take the fuse out of the ABS, repeat the drag-test, and see if the two coasting distances are the same...
Okay...put the fuse back in the ABS.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
PolicySpy wrote:

Not if you have good brakes, good reflexes, and aren't afraid to give the brake pedal a good healthy shove. A car will stop a heck of a lot faster than most people have ever braked. If you're truly panic stopping, as in if you need to stop RIGHT NOW and don't know if you have enough space to do it but gosh darn it you're going to try, on dry asphalt and you don't feel the ABS kicking in (ASSuming an ABS-equipped car) you're not pushing hard enough.
Now, in a non-ABS car, the trick is to NOT lock up the wheels - because the coefficient of friction between tires and asphalt is significantly less when sliding as opposed to rolling - but to get as close to that point as you can without actually locking the tires. In practice what happens is a good driver will stab the pedal hard, then let off slightly when he feels the wheels starting to lock, but no more than necessary to keep 'em rolling. Only way to do that is practice...
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Nate Nagel wrote:

Forgot to mention, getting a little OT... tires play a big role in braking performance. Some tires have so little traction that they are trivially easy to lock up, when braking not much more assertively than normal. GOOD tires will smash your eyeballs against the back of your glasses when you really mash the stop pedal. You ought to be able to panic stop at close to or above 1G on dry asphalt in a modern car with good tires.
Examples of the former category of tire that I've experienced would be the Goodyear Integritys that GM seems to put on everything, or the Continental all-seasons that came stock on my '02 GTI (why you'd equip a car with so much torque with such lousy tires I'll never understand - maybe the ease of doing big, smoky burnouts was a selling point?) or General Ameri-anythings. The latter category includes, in my experience, anything with Michelin Pilot on the sidewall...
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Nate Nagel wrote:

No...electronic-brake-balance and modern tires...eliminates wheel lock up on dry pavement...when the wheels are pointed straight.
Now race cars have mechanical-brake-balance and no problem with wheel lock-up during a long, long, history of motorsports. In fact in setting up a race car...there is only brake size, rotor size, tire size, and mechanical-brake-balance. Well...a race car brakes the same way every time and only needs one brake-balance rather than a variable brake-balance of an electronic-brake-balance. But again...there can be uphills and downhills on a racetrack so the most modern race cars MIGHT have an electronic-brake-balance.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

PolicySpy wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No, sorry. That is just not true.
ABS will prevent lock-up, not modern tires, not "electronic-brake-balance"

I don't think you even know whether "electronic-brake-balance" even exists.
--
Alan Baker
Vancouver, British Columbia
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Alan Baker wrote:

PolicySpy wrote:
With the correct amount of brake-balance...there is no wheel lock-up on dry pavement with the wheels pointed straight. (On most race cars there is no adjustment other than brake-balance. Now modern street cars have...electronic-brake-balance that reduces brake hydraulic pressure to the rear brakes as the brake pedal is pushed harder.)
ABS essentially unlocks a wheel that is locked-up. Well...a wheel approaching lock-up is turning slowly...and then the ABS kicks-in. So ABS most often works on slick roads or when emergency braking with the wheels turned...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'm sorry, but you're wrong.
No amount of "balance" can overcome the fact that the brakes of a modern automobile are powerful enough to lock the wheels.

...or with wheels straight.
--
Alan Baker
Vancouver, British Columbia
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Alan Baker wrote:

For a loose definition of "modern." It's quite possible to get wheel lockup in my '55 Stude with manual drum brakes. Very good manual drum brakes, but still.
*NOT* being able to lock the wheels on dry pavement is a sign that your brakes aren't good enough.
Nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Alan Baker wrote:

Since when could cars NOT lock their wheels?!? The 30s maybe? My 1949 Plmouth Coupe certainly can lock its wheels when I stand on it (with no power brakes at that, but it does have 6 wheel cylinders.)
Brake proportioning valves (what you guys are calling "balance") came into existence way back in the 50s or earlier. Their job is to take all 4 wheels to lockup at the same time, not have the rears lock far before the fronts reach maximum braking potential or vice-versa. Proportioning can't compensate for one or more wheels being on slipperier pavement than the others, but it can and DOES equalize all 4 wheels when they have the same traction (allowing for weight transfer from rear to front as well). ABS does the fine-tuning to keep an individual wheel from locking, or its supposed to. What drivers fail to realize is that when ABS kicks in, you are BY DEFINITION using less than 100% of the car's braking ability. You sacrifice braking power to improve CONTROL during braking. Something that's really best done by a competent driver, not by a machine.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

My first car was a 37 chev. It could lock up on dry pavement.
Harry K
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
PolicySpy wrote:

Then you're not pushing on the brake pedal hard enough. (assuming you want to "panic stop.")
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
PolicySpy wrote:

Not necessarily- that depends on the ABS implementation. Better ABS systems still have a mechanical proportioning valve assembly so that the front/rear bias is correct even without ABS. Only the low-end crap uses ABS as a hack-job approximation to brake balance.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Nate Nagel wrote:

Threshold braking is a lost art. I currently don't own a vehicle with ABS. The last vehicle I had with ABS spent the last 8 years of its existence with the ABS fuses (controller and pump) removed and with the warning light bulb removed. It stopped rather better than it did with ABS, and a LOT better than it did when the abs started throwing error codes.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

In 45 years of driving, I have _never_ been in a situation where I needed antilock brakes. How do I know? Because I haven't slid into anything before having AL brakes on my Jeep, and not since I got that have I been in a situation where the AL brakes engaged in a situation that would otherwise have produced a crash.
I _DID_, however, become a passenger in my own car that _SLID_ out into an intersection from a gravel road that caused the AL brakes to work extremely poorly, and allow the car to roll into the intersection, where a regular set of brakes would have stopped easily well in advance of the intersection, but caught my driver by complete surprise. If the other driver at that intersction at the time hadn't been paying attention, my AL brakes would have gotten us hurt.
Repeal absolutely ALL laws that REQUIRE that there be a particular "safety device" on cars and simply make laws that make them available. I then will not have to buy air bags, AL brakes, traction control, etc. etc., my car will cost a _lot_ less, and I won't have the weight of these historically useless items dragging down my fuel economy for the next 10 years of my ownership of the car in question, which is how long I have to own one now because they are so friggin' expensive... due in part to all those useless things that are mandated by law, against my will, and that I have to buy anyway.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Good for you. Your experience does not mirror every other driver's experience though, especially those that drive on icy and snowy roads. That is where the new braking system does its best work. When I was 16 and just started todrive, I had one experience with sliding on a snow covered road. I learned from it. Some drivers never do.

Sounds like a driver that lacked a bit of experience and was travelling to fast for conditions. Chances are the car would have slid into the intersection anyway, but the fact is, neither of us can prove what would have happened with regular brakes. One bit feature of AL brking sysems is steering control. With wheels locked, you have none.
If the other driver at that intersction

If your driver had been paying attention, the situation would now have occurred in the first place. .
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ed Pawlowski wrote:

AGREE heartedly with Ed on this one. For the average driver, ABS is a godsend in maintaining control while quickly reducing vehicle energy. And, insurance rates seem to support this thinking.
Agree also that under competitive driving conditions a well trained driver with heightened reactions can probably do better without ESC or ABS. That ability is probably good for a couple of hours at the wheel. But, at the end of a driving day, with twilight conditions and a longer complex reaction time, ABS can be a winner.
A downside is the tread damage that results from the staccato/machine-gun brake application one gets from ABS. After an aggressive ABS 'incident' it's a good idea to at least rotate tires or consider replacing them. Unless one does that, a set of brake discs will soon need aggressive resurfacing.
-- pj
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I started driving in NW Ohio, where there was a lot of ice and snow from 1963 - 1983 when I left for... central Indiana where there was still some ice and snow.

I've slid on a lot of snow-covered roads. Its inevitable, even with AL braking. Stuff happens, and black ice rules, period.
Most memorable _not_ sliding was coming back from working a road rally in Michigan, and encountering some fairly pretty, fairly smooth, fairly deadly ice all over a really long bridge on I-475 around Toledo. Saw what was coming, lined the car up to enter the bridge straight-on, pushed the clutch in, and coasted all the way across it. But AL brakes or not, you're going for a ride if you attempt to change anything about your speed or direction on such a bridge.

He's very experienced, and _any_ speed on gravel with that car and it's AL brakes is "too fast for conditions." The best way to stop on gravel is to "lock 'em up." Its a fact. AL brakes make things _worse_ on gravel, not better.

Absolutely not. I have _lots_ of experience with gravel driving, and any normally-braked car would have stoped probably something like 15 ft short of the intersection with a maximum stop.

But it isn't hard to prove that a normally-braked car will out-stop an AL braked car severely on gravel.

Yeah, if you're boneheaded enough to hold the brake all the way down and not let the wheels turn, you have no control. Release them a bit, and you can steer - IOW, pump the brakes.
The situations where the difference between this method and the AL braking method meaning the difference between a crash and no crash are extremely rare. Most of the stuff you were going to hit with a regular braked car, you'll hit anyway with an AL braked car. Most of the stuff you were not going to hit with an AL braked car, you're not going to hit with a normally braked car anyway. The only real difference is knowing enough not to go sliding off into the weeds if you try to brake to the max - if you're experienced, you can do it. If you're not, you _might_ not slide into the weed in an AL braked car, whereas you would with a normally braked car.
Thats why I can be just as safe in either car, and don't need to be paying extra $$$ for the extra equipment that is also just something else to break down and need repair.

He was paying attention just fine - there was just no way to drive that thing on gravel reasonbly and expect to be safe, other than maybe pulling the wire for the AL brakes. That was a '93 Jeep Cherokee. My 98 Jeep Cherokee seems to do a little better, but is also kind of scary. The Subaru WRX does a lot better, although on gravel, I would still rather not have the AL.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Dave Head wrote:

We did an off road test with some Jeep TJ's with ABS after the first one following the old CJ7's and YJ's over a ravine top and down the other side had a losing argument with this tree you had to stop to avoid before a turn. The TJ owner just couldn't stop, his wheels wouldn't lock and he calmly just rammed the tree.
So the damage was done and he was convinced to try again. This time with the ABS fuses out. Well no surprise, he had no trouble at all stopping before the tree.
So he was a real good sport and as curious as we were so he put the fuses back in and tried again. Well, once again he calmly rolled into the tree, there was just no way to stop.
Note: If this tree hadn't been there, it was a sheer drop...
We have since done many more downhill dirt tests like that and now I always recommend if you plan on following me in my old CJ7 off road, you need to pull some fuses....
Thankfully my 2000 Cherokee doesn't have ABS, that might have been a deal breaker...
Mike 86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00 2000 Cherokee Sport 'New' frame and everything else in '09. Some Canadian Bush Trip and Build Photos: http://mikeromainjeeptrips.shutterfly.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

He should try it sober and see what the result is.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.