No ABS?

[Hallen]

In my context, we've seen problems with an E30 going into a braking zone and when you go to the pedal, the pedal is rock hard and you have no braking at all. Not a good feeling when you are 10/10ths on track doing 120+ at the end of the straight. You have to get off the brakes for a slight moment, somehow they cycle, then you get back on the brakes and you have brakes. Problem is if you really leave your braking to the last bit, then to have to get off the brakes means there is no way you will make the turn. Thus the big off and possibly a wrecked car if there is not good runoff.

The ABS on an E30 is really rudimentary. We think it is more designed for the occasional use in the wet, but not in a high performance setting as a routine way to slow the car.

I've experienced it once while driving another PRO-3 car in an enduro, when we had 4 drivers doing stints in the car. Got the rock hard brake pedal going into T1 at Portland. It does not happen every lap, so you don't know when you'll get it, and when the brakes will be OK.

Thanks Lance, that's good to know. I will be doing the first track day for my E30 without the ABS. It is currently disabled. That wasn't by choice necessarily, I just didn't have time to fix it. I will just have to be careful on cold tires and work my way up to speed. I would do that anyway since it is a new to me car and I have done tons of work on it so I need to approach things methodically.

[jlevie]

I had always thought of threshold braking as being just to the point of ABS activation until I did a Skip Barber racing school in Formula cars. They have no ABS (or brake boost for that matter) and we spent a good part of one morning learning to threshold brake. True threshold braking is past the point that a street ABS system activates.

Threshold braking means enough brakes to keep the tires at the point where there's some slip. In this regime the car sort of squirms under braking with very small oscillations in yaw as one side of the car gains and losses grip. That's obviously past the point where ABS would activate. And once triggered the ABS will remain engaged to a point well below the trigger point (the logic has to have hysteresis). I suspect that the ABS system on an E30 probably can't maintain more than about 85% of what's possible and the system found on late model BMW's probably tops out around 90%. And I've heard numbers in that range from the instructors at Skip Barber racing schools. A multi-channel race ABS raises those numbers to the point where it is worthwhile to have.

[Emre]

I currently have ABS in my track car (a '91 318is). But I still threshold brake. The ABS hardly ever comes on. If I start to feel it coming in, I'll back off a bit until I'm threshold braking again. I've gotten to the point where I literally cannot remember the last time I've triggered my ABS in the dry, though it does kick in from time to time in the wet.

Basically, the system is there in case of emergencies, but not something I rely on. I think this is in keeping with how the system was designed to be used.

[Lance Racing]

What is this "dreaded ABS lockout" that you mentioned?

In my context, we've seen problems with an E30 going into a braking zone and when you go to the pedal, the pedal is rock hard and you have no braking at all. Not a good feeling when you are 10/10ths on track doing 120+ at the end of the straight. You have to get off the brakes for a slight moment, somehow they cycle, then you get back on the brakes and you have brakes. Problem is if you really leave your braking to the last bit, then to have to get off the brakes means there is no way you will make the turn. Thus the big off and possibly a wrecked car if there is not good runoff.

The ABS on an E30 is really rudimentary. We think it is more designed for the occasional use in the wet, but not in a high performance setting as a routine way to slow the car.

I've experienced it once while driving another PRO-3 car in an enduro, when we had 4 drivers doing stints in the car. Got the rock hard brake pedal going into T1 at Portland. It does not happen every lap, so you don't know when you'll get it, and when the brakes will be OK.

[george graves]

details(on the 4 channel ABS)?

[PiercedE30]

"Dreaded ABS Lockout" is when the ABS system fails for one reason or another.

I will be excited to try out the 4 channel ABS that I will start working on later this summer.

[Hallen]

Shouldn't you be unpacking your car at Portland right now? :)
I hope to be up there on Sunday, I will try and stop by and say hi.
Monday will be my first track day with my dedicated track rat E30 that I have been building for the last three months. The ABS is non-functional right now... it's most likely the relay but I haven't checked.
What is this "dreaded ABS lockout" that you mentioned?

[Lance Racing]

What are your goals for driving? If your goal is to be a better driver, then lose the ABS. If you are going to keep ABS, then might as well drive an automatic so you don't have to learn the art of shifting either!

I've raced an E30 for 7 years and instructed with our local BMW club for 15. My race car has never run with ABS. And I never felt I was being out-braked by other E30s on the track with ABS. In fact, a couple of them have had the dreaded ABS lockout and had no brakes at the worst possible moment and had big crashes.

Our class (PRO-3) last year banned ABS (there are 25+ E30s in the class), in part because our class is about driving skill and we wanted everyone in the class to be able to really learn to use the brake pedal and not just stand on the brake pedal and have the ABS do the work for them. For those that fear flat spotting a couple of tires, just learn to use the brakes skillfully. I've only flat spotted 2 tires in 7 years. Also, you won't flat spot 4 tires at once. If you are marginally over-braking the car, only one tire will lock up. If you are locking up 2 or more tires you are over-braking the car WAY to much.

Oh, because we run a spec class, the brake rotors and calipers must be stock. We are able to run an aftermarket pad.

Anyone can drive the car from apex to track-out. Anyone can go down the straight and go through the gears. Good drivers are able to brake and carry good speed through the first third of the turn. That is what separates the good from merely average drivers.

[einstein57]

i've never had any e30 with functional ABS. Come to think of it inly one out of the 10+ cars i've owned had ABS. I think if one day my ABS actually worked it would scare the crap out of me.

[danny325is]

Erik,
I would disable the ABS for now and see how you like it and you better test it for a while in both the WET and the Dry. You may be great in the dry but the moment the track gets wet you will be sliding all over the place.

You can disable it by pulling the ABS relay. see pics of the relay here. http://peakracer.com/peak-racer-race...abs-relay.html

my 2cents, unless your a pro driver, there nothing that can hurt you by keeping the ABS. I know we all dream about being that pro driver ( just ask Ranger) those rides are few and far between. when you turn pro you can have your pit crew take out the ABS while you sit in the motorhome with all the babes.

[E30 Racer]

...lets say that max braking occurs at 10% wheel slip...at what point does E30 ABS kick in? Maybe 1% slip? Maybe 50% slip? That's the crux of the issue. In order for ABS to be more effective, it has to restrain itself from kicking in too early, and then only reduce wheel slip to 10% (in this example). If it reduces wheel slip to 0, then the potential for being a hinderence is there.

The ABS threshold will vary somewhat, depending on how much friction is available (i.e., what surface you're on). That said, ABS should be expected to activate once an allowable slip level has been exceeded, not before.

Just a point of reference, 0% slip = a free rolling wheel. 100% = a locked wheel.

[RangerGress]

Disable ABS by removing the little rectangular relay that is under the dash above driver's left knee. The relay is not on a board of relay's, it's by itself.

E30 Racer, I figure that anyone that knows what a "Hall Affect" is, is worth listening to. But just to doublecheck that I understand...lets say that max braking occurs at 10% wheel slip...at what point does E30 ABS kick in? Maybe 1% slip? Maybe 50% slip? That's the crux of the issue. In order for ABS to be more effective, it has to restrain itself from kicking in too early, and then only reduce wheel slip to 10% (in this example). If it reduces wheel slip to 0, then the potential for being a hinderence is there.

I'm not disagreeing overall. I'm happier now that my ABS is working again. But it's good to understand exactly how things work, instead of just sort of understanding how things work. And the way to understanding is to ask questions. So I'm asking.

[SimonH]

This thread is making the rounds :D. He's my take. I'm faster with the ABS period. I love hearing people turning off their ABS because they "think" they are faster or can brake better. Honestly if you can threshold brake better than the ABS system lap after lap then you should be driving professionally. I could go on but I won't bore you. Now your braking system is a little different since you don't have a booster and it is a custom setup. At least with that setup i'm guessing you will have an easier time driving with out the abs and being able to feel the lock up. Having said that being able to drive without the ABS is a good skill to have, it will give you a good understanding of where the real threshold is without it being masked by the ABS and if heaven forbid your ABS does fail you won't flat spot all 4 tires in the very next corner. If you want to try that go for it, put on some old tires though . Overall I don't recommend running without it, unless there is something wrong with your system.

[BrewCity11]

^ good comments

I would have to agree.

I would disable it first before completely removing it. Did anyone answer the OP's question about how to correctly disable it?

[E30 Racer]

ABS is the anti-blocking system. It keeps the wheels for locking up. A locked wheel will have much less stopping power than a wheel at the threshold. Older cars such as e30s had a rather primitive ABS programming (still much better than its US counter part of the days). If one wheel locks, it kicks back on the rake pedal releasing all four wheels.

This is absolutely false. The ABS (antilock braking system) monitors wheel speed via hall effect sensors at each corner of the vehicle. When a wheel begins to lock (known as longitudinal wheel slip), the ABS will reduce the amount of brake line pressure of the effected brake circuit (NOT necessarily at each wheel unless each wheel is demonstrating a propensity to lock). The reduced brake line pressure allows the effected wheel to regain some rotation, and the cycle repeats. On dry pavement, maximum braking occurs at approximately 15-20% wheel slip.

Generally speaking, even professional drivers will be unable to outperform the stopping distances achieved by ABS.

I would, without question, encourage drivers to retain ABS on their cars (especially if they are street driven). Once you are able to achieve consistent lap times, and feel like ABS may be adversely affecting your lap times, disable it and see what happens. Only then will you be able to conclusively determine whether *you* are better off without it.