Brake Failure & Wreck in E36 M3 at VIR-ICE MODE ????

oldschoolZ said:
Great story ! WC GT cars nowadays are allowed to run ABS, FIA GT3-based cars like the R8 LMS run a full on race ABS.

Less fortunate teams are retrofitting OEM ABS pumps from high performance vehicles and re-programming them to save on costs, so yeah street car ABS is definitely quicker than no-ABS.

Edit: turner Motorsport sells a racing ABS that uses OEM E46 M3 servo-valve, street ABS can't be that bad can it ?
http://www.turnermotorsport.com/p-3798-racing-abs-wiring-harness.aspx
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WC GT and up have always been allowed ABS- I am pretty sure- just TC got the ax- blame it on shitty factory ABS..lol

The 2 cars I track have factory ABs still activated and it is way more effective than without. The ITR had a shot sensor last year and I tried trail braking it like that and the rear lock up was wild.
Several years ago when Grand Am visited GP3R, my ITR was parked in the paddock- I was racing the bitch with Vince.- and some US based team came to see me to borrow my ABS sensors from my car- theirs got fried and they absolutely wanted their ITR to have ABS.....so I guess they can be somewhat effective...
 
All I can add is this.

Mid session end of August in 2010 in the Audi, arriving at the chicane after having made a pass, brake pedal goes to the floor with little or no braking power, just out of instinct I recycled the brake pedal and had full brakes, negotiated the corner without much incident. Had no issues the remainder of the session.

I was baffled at the time, I asked everyone at ASE, no one had a clue what I was talking about.

I distinctly remember being upset because everyone's initial reaction was brake system temp issues, but no one could explain why I had full brakes a second later. I ended up just letting it go. It's never happened to me in the M3.
 
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Thanx Steph !
If it's our chicane at ASE, it's not bumpy, so possibly wheel lock itself may initiate this.
I would guess that the Audi would be more designed to use traction more than RWD and FWD.

Have a look at your owners manual, and get ready for a surprise. :yikes:

Here is mine for BOTH the Z3 and the 328is 1997

This is also for you Sebdavid which may formally confirm my previous opinion:

Owners Manual BMW Z3, 3 series 1997

Direct quote:

Brakes

Winter road conditions substantially reduce the amount of traction available between the tires and the road surface; the resulting (considerable) increases in braking distance should be continually borne in mind.

ABS prevents the wheels from locking when braking; the vehicle remains stable and sensitive to steering inputs.
Should the ABS fail,with locking wheels as a result:
Reduce the pressure on the brake pedal just to roll again while still maintaining enough force to continue braking.Then increase the pressure, release the pressure when the wheels lock, reapply pressure, etc.This staggered braking procedure will reduce stopping distances while helping you to maintain steering control.It allows you to steer around hazards once you have reduced the pressure on the brake pedal.

Never downshift to exploit engine braking when driving on slippery road surfaces; it could lead to loss of rear- wheel traction and endanger vehicle control.ABS and ASC+T do not provide protection against this kind of traction loss.
 
Steph, perhaps some air in the system? Or, and this happens a lot on Corvettes, it could be pad knocback. If you have a somewhat loose hub this is more likely to happen: bumps etc. push the pads farther away from the rotor, increasing the pedal travel needed to make contact with the rotor and brake the car. A quick release and reapplication of the brakes fixes it. Guys who get it regularly tap the brakes with their left foot before the actual brake application.

When getting fluid-related brake fade, it can also help to pump the brakes once, to get rid of the slop caused by the air in the system (because the fluid boiled). This may also have been what happened.

Dave, I don't see how the quotes you give add anything to the discussion; they just describe the way ABS works, and what you should do if it fails (i.e. cadence or pump braking). I certainly see no evidence of "ice mode" in there.

I'll repeat how I understand ABS to work in low-traction circumstances: ABS works - wheels can't lock, braking power reduced to maximum available traction (which can be very little if on ice), pedal pulsates. Pedal does NOT go to the ground, brake bias does NOT go to the rear. ABS doesn't work - wheels can lock, so pumping the brakes to simulate the same effect and find maximum braking power is the only option (in an emergency situation).

I still don't see why any engineer would program in a mode into the ABS that allows the pedal to go to the floor for any reason.
 
Sebdavid said:
Dave, I don't see how the quotes you give add anything to the discussion; they just describe the way ABS works, and what you should do if it fails (i.e. cadence or pump braking). I certainly see no evidence of "ice mode" in there.

I'll repeat how I understand ABS to work in low-traction circumstances: ABS works - wheels can't lock, braking power reduced to maximum available traction (which can be very little if on ice), pedal pulsates. Pedal does NOT go to the ground, brake bias does NOT go to the rear. ABS doesn't work - wheels can lock, so pumping the brakes to simulate the same effect and find maximum braking power is the only option (in an emergency situation).

I still don't see why any engineer would program in a mode into the ABS that allows the pedal to go to the floor for any reason.
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Maybe to force the driver to reset the brakes and regain some kind of steering ?

That's why I quoted the manual:
This staggered braking procedure will reduce stopping distances while helping you to maintain steering control.It allows you to steer around hazards once you have reduced the pressure on the brake pedal.

Kinda iffy on a race track though....
 
Dave... ABS is what lets you keep steering by preventing locking the wheels. If ABS works, you don't need to "pump" the brakes or "reset" pedal pressure to keep steering control, that's what ABS is for. The procedure they describe is in the event ABS FAILS, in which case you do "cadence braking" or pump the pedal in order to regain steering, as this will simulate ABS by preventing the lockup (which happened because ABS isn't working).

I don't know how to explain it better. There is nothing in your manual about "ice mode". It would be a stupid useless thing to program in an ABS system. I'm pretty sure it doesn't exist.
 
Seb, I agree with you , " ice mode" is a term that drivers are using to describe this issue.
I sincerely doubt that Bosch would be willing to discuss any inner workings of the product.
BMW actually refers to this as a failure.

And the issue is that we may be creating ABS failure by pushing the vehicle past it's programmed limits.

It's what we do after that is important !

I believe that anyone who read this thread will know ! :D
 
I've had my brakes have a weird fit at ASE. It was my first time driving a car with ABS on the track and the car's brake were neither over heating or in bad shape. From what I remember, I think I braked late and a little hard in the paddock's straight and probably locked a wheel a bit and right away, my pedal went to the floor just as I was about to trail brake in the curve. I straighten the wheel back and released the brake to brake again, used all the space available and took it from there.

It was quite upsetting.
 
New information

^ Glad you were able to recover ! *tu*

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I found this video which may provide a bit more insight.

Press here

Maybe a bit too Late braking ?

...and a pretty good demonstration why not to follow.
 
Shardik said:
^ Glad you were able to recover ! *tu*

----------------------------------------------------

I found this video which may provide a bit more insight.

Press here

Maybe a bit too Late braking ?

...and a pretty good demonstration why not to follow.
Click to expand...

Glad the old man was not the one flagging people out of the paddock that day... I was clearly late on the braking.
 
ABS Ice mode update

hi guys, I have an update on ABS ice mode and what causes it to come in...

This weekend I was in Brazil for my first race weekend working as no.2 engineer on a Porsche 997RSR in the World Endurance Championship (WEC). Needless to say I love my new job, coming out of school it's the best I could ask for !

The team I work also run a GT3R (ABS and TC) in the FIA GT3 series. I was talking to the chief engineer about how the ABS system is calibrated to differentiate low grip wet conditions with high grip dry conditions and how it detemines each situation.

Here's some explaination as to why ice mode willt come in, even a dry track surface: (lengthy explaination)

Imagine the stock car running in a straight line and the driver going hard on the brakes to make the ABS come in:

1. The car pitches forward, it has a fast pitching speed.
2. The ABS system senses the brake pressure rising AND the car pitching forward quickly.
3. The dampers react to the pitching motion and the car stabilises with a pitch angle.
4. If the ABS system senses a brake lockup, it modulates the pressure.
5. Driver releases the brakes and turns in, no problems here.


Imagine the same car with aftermarket springs and shocks running in a straight line and the driver going hard on the brakes to make the ABS come in:

1. The car pitches forward, it has a slower pitching speed because the aftermarket dampers are stiffer
2. The ABS system senses the brake pressure rising...but the pitching speed is slower because of the aftermarket dampers.

- Now, which situation causes a large rise in brake pressure and a slow pitching speed ? Hard braking on ice ! The brake pressure rises quickly, but since the car has no grip, the car pitches forward very slowly

3. The ABS releases the pressure so much that the wheel isn't even allowed to slip a little bit, think about it as threshold braking but on ice.

- Why does ice mode even exist ? Well, the simple explaination is that for the wheel to slip on ice and lose grip, there has to be a film of water forming between the tire and the ice (like ice skating). If that water film forms, there's even less grip to be had.

4. Car crashes, driver complains and no one understands :p


So, basically it's caused by the increased bump damping in the front and increased rebound damping in the rear.

Makes sense?!?
 
Great thread, first time i read it ... i'm happy because I was wondering if it would be better / safer to run my ITR without ABS.
I guess it was Worth the $ to repair the abs motor when i got the caR
 
oldschoolZ said:
This weekend I was in Brazil for my first race weekend working as no.2 engineer on a Porsche 997RSR in the World Endurance Championship (WEC). Needless to say I love my new job, coming out of school it's the best I could ask for !
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First of all, we want to hear more about this. Separate thread to tell the story please!*tu*

Second, yes it makes total sense except that in that situation the pedal wouldn't go to the floor as it apparently has in all those "ice mode" stories. Pedal going to the floor can't be a design feature of some ice mode. It points to some other problem. Pad knockback maybe.
 
Sebdavid said:
First of all, we want to hear more about this. Separate thread to tell the story please!*tu*

Second, yes it makes total sense except that in that situation the pedal wouldn't go to the floor as it apparently has in all those "ice mode" stories. Pedal going to the floor can't be a design feature of some ice mode. It points to some other problem. Pad knockback maybe.
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Yes, could be pad knockback, but the pedal going all the way to the floor would make sense if A LOT of pressure needs to released off the system to make the wheels not lock up ?

I will make a thread about my weekend ! Next race is in Texas in 2 weeks, then Fuji, Shanghai and Barhain.
 
oldschoolZ said:
Yes, could be pad knockback, but the pedal going all the way to the floor would make sense if A LOT of pressure needs to released off the system to make the wheels not lock up ?
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On all cars I've driven, when ABS engages, pedal stays hard and starts pulsing. It does NOT go down to the floor when the ABS system takes braking pressure away. From what I understand, pedal to the floor = fluid boiling and therefore air bubbles compressing, or pad knockback meaning pads are far from rotor surface and need lots of pedal travel to get to the firepath (or of course sudden leak in system). Hard pedal and no braking is pad fade, i.e. pad overheats and friction just doesn't happen as it should (happened to me in an F430 once :yikes:) or if the pedal is pulsing, ABS intervention, which can be premature under certain circumstances.

As I mentioned before, (when my damn ABS works) I've gotten premature ABS intervention many times when I go for the brakes and the car is already unsettled, with slip angle or a wheel off the ground. I get reduced braking pressure but my pedal is hard and pulsing for a fraction of a second, then ABS figures out what's up and gives me my brakes back. But it doesn't go to the floor. I unfortunately didn't run with ABS on the M3 long enough (too cheap to fix it) to really test it out on the track.
 
Could it be pad knockback combined with ABS ice mode then ? If not, I still don't understand how the pedal would go to the floor, except for fluid boiling, internal leak or pad knockback like you mentioned... I need to dismantle an ABS pump to really understand what could cause this :p

I.E. if you had hard cornering followed by a hard braking zone ? Pads get knocked back, unfortunately ABS thinks you're on ice since your aftermarket shocks have stiffer damping, ICE mode comes in, pedal to the floor. Definitely could happen !


Funny story about pad knockback:

A friend of mine works in IndyCar as a Data Engineer, that weekend they had BIG pad knockback issues. They used anti knockback springs in the calipers: they're small cone shaped springs inserted behind the piston to keep the pad slightly pressed against the disc. They tried different stiffnesses but the issue would always be there.

They finally figured it was the brake ducts that were too big, the air pressure in them was so great (300km/h + car) that the pad would be pressed back in no matter which springs they used !
 
Speaking of ITR stories, I can confirm from first hand experience that on a miserable, cold, rainy late september day at Sanair paddocks, ITR ABS + Full tread RA1s = enough Gs to splatter unsuspecting shot-gun riding Carl into the dash/windshield... :yikes: :D
 
BBQMAN said:
Funny story about ABS- for those who think that street car ABS cannot be track worthy.

In 1999- World Challenge cars from Real Time Racing- the Itrs at that point, finished a race 1-2-3. That was pretty normal for this dominant team at the time, except that they finished 1 lap ahead of p4. The conditions were treacherous rain and the FWD ITRs dominated in touring class. In the post race interview with P Kleinubing, he mentioned that it was a good race, largely due to the superior ABS control in the ITRs- stock OEM ABS- not race ABS.
the cars were so dominant in the rain and low traction conditions that SCCA techs went on to ban ABS in Touring class WC cars.

Yeah real world street ABs must really be bad.

That said, this video and other info released afterwards points to much fail on the drivers part. IMO, he blew the corner- plain and simple. Blaming ABS is easy when you don't know what you did wrong in the first place.

Apparently this guy tracks his car with loaned helmets- that do not fit and missing key safety equipement- so its likely he was in over his head approaching T1.

My 2 cents...
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I agree, I don't understand how ABS can possible be a 'bad thing' on the track if you take it into account when planning your braking zones. If you know how your car will react in a given situation, you will be able to drive it just fine. I've run ABS/no ABS, and they are different, not 'better' or 'worse.'
 
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