First question about ABS

[mason]

A traditional Elise does not come with power assist or ABS brakes, as Lotus believes that anything that “insulates” the driver from the car should be avoided.

Because of the weight of the US Elise Lotus has decided that assisted brakes and ABS will be standard equipment. The ABS system in the Elise is reported to be setup for spirited driving and not to interfere unless absolutely necessary.

It seems like the general perception of ABS is that it’s bad for any kind of motor sports application, how do you feel about it and what would consider the strengths and weaknesses of ABS for motor sports?

[DFauth]

This must be the most divisive, controversial question between automotive purists and pragmatists I've ever heard. I don't think that anyone can, given the current technology and ideal and dry conditions, argue that an ABS-equipped driver can stop more quickly than a non-ABS equipped driver. Until the technology reaches a point where ABS comes into play PRIOR to wheel lockup, there will always be that tiny edge of adhesion that an analog-based human can ride along that a digitally-based ABS computer cannot access.

Now that we've gotten that disclaimer out of the way, let's look at the practical applications...

Autocross:
The nature of autox is such that incredibly quick, hard braking is done for, typically, only a few fractions of a second. This is one case where ABS becomes a pretty nice feature. How many people believe that they can hit the brakes, achieve maximum braking, and release in less than half a second? I know that I can't do it consistently without getting some brake lockup! Autox braking can be broken down to a few panicked moments of fierce braking. The main thing provided by ABS in this situation is consistency. Given only 3 tries at a course, would you like to throw out one of those runs in search of the perfect braking? I didn't think so. What it comes down to in autox is that there is no perfect run. There are good, great, even spectacular runs, but no *perfect* runs. Given that, the best you can hope to do is to minimize your mistakes (that is, any time when you're not maximizing the car on your ideal line)

Track:
On a road course (or oval that requires braking), the braking zones are generally very long (especially when compared to autocross). As such, you generally have a good amount of time to modulate the brakes in order to obtain the ideal amount of braking force given the conditions and the dynamic condition of the car (slight turn, etc.). In addition, unless you have some amazing brakes or an incredibly light car (Elise???), you can't do max braking for very long before you start to get fade. That's life in road racing...you need to conserve the car (oil temp, tire wear, brakes, etc.) in order to make sure you can make it to the end of the race. Does having the satisfaction of fast lap of the race really make up for the fact that you didn't finish because you used up your car too quickly? Obviously, if you're not doing threshold braking all the time, the consistency of ABS wouldn't make much sense in most of the cases on a track. Go ahead and save the weight! However, it's a different story if you throw poor conditions into the mix. If you've got to nurse your car back to the pits on a wet track to put on your rain tires, do you want to risk an "off" because you didn't react quickly enough (ABS will, IMHO, react more quickly) to your sudden brake lockup due to momentary hydroplaning? It comes back to consistency and having a safety net in case the worst happens. No, it won't necessarily make you stop more quickly, but it will do it consistently and keep you in the race.

Anyone have any other thoughts or arguments? Who knows, I could be wrong.

[mikester]

DFauth, I think that your input raises some interesting points, one of which I would like to quibble with a bit, and that is your comment that ABS stops quicker than non-ABS etc. While this may very well be correct (probably so for perhaps all but the most experienced professionals, not sure), I have always been under the impression that this is a bit of a red herring. What I mean is this - that while many drivers have been led to believe that that's ABS' main advantage - to stop quicker - that in fact, ABS may or may not stop you quicker (in a panic situation), but what ABS absolutely will do for you is to allow you to maintain directional control while you have that brake pedal to the floor. Unfortunately, most drivers have not been told this, or have not read it in their car's manual, or even if they did (once, long ago), have forgotten it, and will not use this capability when they need to know it (in that emergency situation). Consequently, many accidents occur in cars equipped with ABS which could be avoided, simply by drivers steering around the obstacle, while panic-braking. Instead, they panic-brake and drive right into that obstacle.

I realize that none of this has direct application to motorsport really , so I'm off-topic - but still I wanted to throw that out there, for general consumption and understanding. Basically, what I'm advocating here is for people to train under controlled conditions, and learn what your car is/is not capable of, before you need to find out the hard way ! This can be done in an advanced drivers training environment, or autocross, etc.

Cheers, Mike

[DFauth]

Originally posted by mikester
DFauth, I think that your input raises some interesting points, one of which I would like to quibble with a bit, and that is your comment that ABS stops quicker than non-ABS etc.

Oops...I think my first paragraph was written in a confusing way. I do NOT actually believe that an ABS-equiped car can stop more quickly. In fact, all else being equal, the expert driver can modulate on the *edge* of adhesion without going over whereas ABS doesn't actually come into play until that edge has come and gone. Thus, the expert driver can, theorhetically, stop more quickly. Whether or not that holds true in practice is the entire point of this thread, right?

[mikester]

Thanks, that was my understanding as well (simply based on what I have heard from those "in the know"), good to hear that you are of (more or less) the same opinion.

Generally, I am of the opinion - strictly as a "couch-racer" (except for a handful of karting sessions, testing only) ABS is not a desireable thing in motorsport, because it is taking away some of the control from the driver - although on the plus-side, no need to worry about flat-spotting your tires, right ?

[thegit]

Imo, the tire will ultimately determine stopping ability. this is complicated by the condition of the tire... full tread, shaved, been nearly flat spotted, its suitability to the road surface, etc.
With David ,I feel that ABS should not be viewed as a stopping weapon... I feel I would be too narrow in thought to rely on ABS as a distance shortener.

I'm more interested in the function and ability of the ABS when the car and driver are experiencing a mix of lateral and longitudinal forces at the same time.

some of us that learned threshold braking before ABS became commonplace may be more curious about achieving maximum braking up to the point just before the ABS kicks in, and the effect of that behaviour on the quality and efficiency of the brake system on the car. For example, on a Corrado SLC I discovered that I was rendering the brakes of the car less efficient by threshold braking up to just below the ABS threshold.
m.

[JLSELISE]

A "prototype" Federal Elise was quite the star of the West Coast Lotus Meet last month, and, re this thread, some of you might be interested in reading the write-up Randy Chase provided to the Golden Gate Lotus Club of his autocross driving experience in the car at the event. You can find it at: http://www.gglotus.org/gghotnews/elisenews.htm There is also an in-car video of one of his runs that you can download from the site. Randy is an SCCA Solo II national champ, and it really showed at the autocross. I was one of the corner/cone watchers while he made his runs (the fastest of the day by about 2 seconds!) and it was clear to me that the ABS on his Elise was an invaluable aid to the car control he had under heavy braking in the very tight, but important, turn-arounds at both ends of the course. He says he never felt the ABS kick in, but that is the way it is supposed to work on the Elise . When I got a chance to drive the course, I was able to borrow a friend's Sun Elise (2001) which has better power-to-weight than the Federal car, but no ABS, of course. I was doing fine (I thought) until I delayed braking too long for one of those tight turn-arounds and promptly plowed off the course. The message is: it really is a big help to be able to brake at the limit and steer at the same time.

[Elise4Laps]

Agree with opinions above .... just wonder for track situations where you lose you car and perhaps spin.

I have never driven an ABS-equipped car on the track, but I have spun my non-ABS a few times and used typical "both feet in - wheel straight" to lock the brakes and slide the car to a stop in a safe, straight trojectory ..... on the pavement if possible. Sure I flat-spotted some tires....but I haven't hit anything thankfully.

I have seen other drivers lose control, and flail their cars around trying to catch it back. One commented after he couldn't seem to lock it up because of ABS, and he hooked back across the track in front of traffic.

How does it work with ABS guys? If you lose the car, CAN you still determine an instant where you want to lockup and do so safely? If NOT, then to me it is the most crutial shortcoming of ABS for track use.

[JLSELISE]

An interesting question, and I don't have an answer based on experience. However, I would speculate that ABS would not decrease the effectiveness of this skid control procedure. The physics is that the maximum braking force is developed just prior to wheel lock up, so having ABS insures that force will be maximized in a wet or dry situation and it would follow that skid control using the "both feet in" technique will also be enhanced by ABS. No matter how much you may try, you simply cannot steer a locked-up wheel--the momentum vector takes over--so it cannot be true that you will have more control of a vehicle with all wheels locked up than you do with a functioning ABS system.

[Jerry McCrimmon]

Regarding ABS on sports cars: 1: Drivers sharp enough to stop shorter without ABS than with it are very very very rare ! If you believe you are one such; I would suggest an experiment : Either mount an accelerometer to the chassis or lay out a strip on tarmac of the type you ordinarly drive (not on a public road!) and actually measure your stopping distance. Take several readings, first with ABS engaged and secondly with it disengaged. Sneak up on full panic stop for if your rear brakes lock first you will swap ends faster than a centrifuge. With ABS disengaged you *must * lock your front brakes before the rears. This way you loose steering control but the care does not become unstable. 2: If you switch tyres on an ABS equipped car (particularly in a car that has different diameter tyres front/rear) that rhe rolling radius remains close to stock or close to the same rolling radius ratio front/back so as not to confuse the ABS computer into thinking it is about to lose it. I do not intend to be tedius; but realize that messing with the design engineering of an automobile can get you killed !! Drive safe Jerome McCrimmon