RSAErick

I love ABS for street-use. Any unexpected braking need is quickly and effectively taken care of by a computer.

However, on the track, I fear that ABS will someday cause a catastrophy.

Imagine this scenario....
Coming through a corner too hot and on the gas. You're exiting the turn too wide when the rear-end steps out on you. You counter-steer, but if you stay on the gas, you're off the track and in a wall. If hit the brakes with ABS, the car hooks up again and shoots you back towards the INSIDE of the track and towards a wall.

If only you didn't have ABS, you could lock 'em up and skid out in the direction your momentum is taking you. It's a spin, but not a disaster.

My feeling is that NOT having ABS gives you ONE MORE OPTION when out on the track: The option to go in the direction of momentum.

Does anyone else feel this way?

Erick

smokey

There have been a number of wrecks at Mosport DE's over the past few years that happened exactly as you described: the car went off track, and the traction on the front wheels (due to ABS) hooked the car into the opposite wall as soon as it came back on track. At our skid schools, the ABS fuse is removed to practice the "in a spin, both feet in" technique. However, I'm not an expert, and I'm sure that in real racing the reduced flat-spotting of tires argues in favour of ABS. There's always a trade-off.

Dbltime

IMHO the benefits of abs far outweigh the any downside (i can't think of any). You can turn in to a corner while still hard braking with abs. Try that with basic brakes.

Only one benefit to non abs that I have witnessed. At the start of a race, green flag drops, tight group of cars heading into turn one hot, everybody gives room to the car smoking and squeeling.

I doubt your back end came around due to your brakes but your early apex or dropped a wheel.

Eric in Chicago

I dont know Erick, If you get on the brakes that hard in the middle of a turn, your going to have issues ABS or not. I almost never get the ABS to kick in at the track. I am not trying to get it to work but with threshold braking it should not. When the car is getting away from you, too much of anything is going to cause a problem (steering input, gas, brake ect.)

Greg Fishman

I agree with Eric in Chicago. If you are going sideways ABS does nothing. Also ABS can not create grip where there is none. Sounds like what Erick describes is a hook slide. The car slides and driver corrects but doesn't unwind and hooks it back the other way. If you have to hit the brakes at the track out point you are screwed, how badly depends on the track and the particular corner.

Greg Fishman

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by bill walczak:
<strong>Only one benefit to non abs that I have witnessed. At the start of a race, green flag drops, tight group of cars heading into turn one hot, everybody gives room to the car smoking and squeeling.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Good one Bill. Maybe you should install a "smoke screen sprayer" for the next race.

Barry Lenoble

Hello Eric,

One flaw in your reasoning: if the rear steps out and you step on
the brakes, the car will NOT 'hook up' but will probably spin even
faster. Getting off the throttle and on the brakes will transfer the
weight off the rear tires and onto the fronts. The rear's don't
have enough grip and you spin. ABS won't stop the spin.

Best thing to do is step on the brakes HARD and hope you stop
before you hit something.

Barry

NetManiac

I don't have any experience with this so I may be way off base. I have yet to be on a track much, less in a race, so I can't comment on Eric's idea/thoughts.

However, this sort of thing occured to me while doing a breaking threshold exercise at a performance driving school. During the exercise ABS enabled drivers were trying to break hard but not to the point of ABS kicking in. Whereas non-ABS enabled drivers were trying to break just before the point of lockup. So a non-ABS car has a shorter breaking zone (and therefore longer straight) than does the ABS car. Giving a non-ABS car a slight advantage. Slight being maybe a foot or two. When your working on seconds (or just getting familiar with the track) like me it doesn't really matter. But if you are trying to shave 0.001 of a second off your time, or trying to get just enough of an edge over the car next to you (I would imagine). Wouldn't it pay off?

So when/if I ever get to that point it would be nice to have an "ABS off" switch like PCM enable cars have for PCM.

Of course like I said I am too new to really know what I'm talking about. This is just a thought/idea I had and thought I would throw it out here.

/net

smokey

The theory behind "in a spin, both feet in (clutch and brake)" is to lock up all four wheels once the spin is clearly unrecoverable, proceeding in a straight line while reducing momentum until the car stops - one way or another. With ABS, the wheels cannot be locked, so this approach is impossible, for better or worse. Jackie Stewart's corollary was: "when in doubt, both feet out".

Bryan Watts

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by smokey:
<strong>With ABS, the wheels cannot be locked, so this approach is impossible, for better or worse.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">IMHO, physics would argue against you.

At the point that the car is spinning and unrecoverable, you have exceeded the tire's ability to make the car turn. Hitting the brakes and inducing ABS does not somehow magically give the tires additional cornering force that wasn't there before. This seems to be the biggest misconception that people have. In fact, hitting the brakes, ABS or not, removes MORE of the tire's ability to turn.

In some cases, the wheels stop spinning while sliing sideways, of only for a split second. At that point, the wheels are moving the same speed, brakes are still applied. Without any variance in speed between the wheels, ABS no longer activates and as long as you continue applying the brakes, the tires should stay locked since the computer no longer senses a problem or speed variance. Think about it...does ABS activate when you hit the brakes at a stand-still even though the brakes are locked? Of course not. Further, I don't believe ABS systems work while the car is rolling backwards, so they should lock once the car goes around...someone correct me if that's incorrect.

Even if ABS continues to activate no matter what, the optimum slip angle of the tire has been exceeded, at which point most tires (particularly R-compounds and race slicks) have a sharp drop off in grip. Applying ANY braking pressure, whether with or without ABS, forces the tires to both try to turn the car and try to slow. If the grip available from the tires is already exceeded while trying to turn (i.e. you are spinning), applying the brakes guarantees that the tires don't have any additional grip left to turn. You'll still spin in a straight line off the track. It all comes back to the traction circle.

I've spun plenty of times in cars with and without ABS. The car does not magically shoot back onto the track as long as you totally commit to both feet in and don't breathe off the brakes subconciously.

Greg Fishman

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Bryan Watts:
<strong> </font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by smokey:
<strong>With ABS, the wheels cannot be locked, so this approach is impossible, for better or worse.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">IMHO, physics would argue against you.

&lt;snip&gt;

Further, I don't believe ABS systems work while the car is rolling backwards, so they should lock once the car goes around...someone correct me if that's incorrect.

</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Bryan,
You are right on target with the first part of your post. I have experienced this first hand many times.

The second part about the brakes locking if you are traveling backwards is not so cut and dried I am afraid. It may depend on the car and the ABS system. I remember my mechanic talking about a device or relay that would override the ABS if you were going backwards. Fortunately I don't have a lot of experience with this type of spin but from what I remember my brakes did lock.

RogerJ

Street ABS is not so hot on the track. If you run a stiff suspension on a bumpy track you will find it kicks on in when you would really prefer it not to. When braking heavily and running over bumps, street ABS freaks out as it trys to deal with the momentary locking that occurs as the wheels bounce over the bumps. What you feel is the car not slowing as you were expecting. Easing off the brakes and then back on brings the system back. Racing ABS deals with this by using longer cycles.

Also, as posted earlier, it is impossible to lock the wheels in a spin, thus greatly increasing your chances of hitting a wall because you can't lock the wheels and keep the car going straight. Racing ABS deals with that by allowing you to increase the pedal pressure to a level where the pressure "pushes through the ABS" and the wheels are locked.

Danno

One thing that's been left out is the specific ABS system and its algorithm. There's a difference between early-generation single-channel vs. dual-channel ABS. The latest incarnation, PSM is the most sophisticated yet and if anything, prevents spinning no matter how hard you try.

The key here is total-traction and going back to the traction-circle to examine your traction-budget will make much more sense. There is only so much traction available and if you're starting to slide laterally, you've overcome all the available traction. No matter what you do at this point, you gotta wait it out as the slide decreases your speed to the point where the total cornering, braking & accel. forces is not greater than the available traction.

Slamming on the brakes with ABS will not suddenly gain you traction where previously there was none.

Bill Gregory

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"><strong> Racing ABS deals with this by using longer cycles. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I don't know much about ABS, but I did remember an interview Jurgen Barth gave, discussing racing ABS, and he said "The RSR 3.8 has the same ABS system as the 911 Turbo GT Le Mans. It's a much more effective system because with normal ABS there are long intervals before it reacts and returns to standard again, which means amplitudes or cycles are long. The racing ABS cycles are short. It enables you to brake much later, deeper, in the corner than you could do with normal ABS, or even with your foot"

Also, the 964 Cup cars had an ABS defeat switch on the master cylinder which reacted to pressure to override the ABS, as well as a manual ABS defeat switch on the dash.

Stuttgart

I don't know anything about spinning off track and ABS, but i do know that with the racing ABS in the 993 Cup car i can outbrake most of the cars in the top race group. I wouldn't take ABS off if you payed me, you just pick your braking point, hit the brakes as hard as you can, and try to keep it on the track as it dances around.