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Discussion Starter · #1 · (Edited)
Hello fellas,

Had some track testing this weekend and had some issues with the brakes. It has happened to me before and it is known as "ABS ICE mode". A common issue on Porsche and Lotus if you google it a bit. I've just recently started to explore this so take the posted info below with a bit of reserve.

So what the ABS ICE mode is?

It's not brake fade due to temp or spongy pedal. Its' a very unpleasant situation when you stomp on the brake pedal and the stopping power just isn't there. The brake pedal gets very stiff and the brake force is very weak. Stopping power is greatly reduced and you usually end going straight in to the corner or even out of the track. It's the issue of ABS thinking the wheels are locked but they are not. Releasing the brakes briefly and then reapplying them again fixes this, but driving on the limit we all know there is no such thing as enough time or space to release and reapply brakes again without missing the apex or even staying on the track.

What triggers it? Overly aggressive brake pads (high initial bite) in combination with foot stomping (sudden, hard step on the brake) is my guess so far. I hadn't had this issues until I started moving up the brake pad range with very high initial bite (high coefficient of friction) and started using left foot braking, where it's much easier to stomp the pedal than by using the right foot which due to the position on the accelerator has to move left and it's angled so the force is not as abrupt as with the left foot. It happens on BBK, standard size discs and OEM discs, so the disc are not the issues.

I experienced this before on Winmax W7 brake pads (high initial bite) and it got worse this time with WN3 (highest initial bite). More progressive applying of the brake pedal force completely eliminates this issue and the car stops amazingly. But stomping on a brake it messes the ABS big time and it makes the car virtually brakeless. It could be the yaw angle sensor, or wheel speed sensor, telling the ABS that the car has exceeded the grip levels. I'm not sure. it's something you probably won't experience on a stock car as the tire grip is not sufficient, neither is the brake pad initial bite.

I'll go for less aggressive front brake pads, while still keeping high friction rears, to see how it changes the effect on the brakes and report back.

Anyone else experienced this?
 

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That's really scary!
I don't think I would have the presence of mind to release the brakes and reapply them slower the second time. I would be off the track for sure.
When you stomp on the brake pedal, this should invoke the Emergency Brake Assist (EBA) function where the brake pressure is boosted to the point where wheel lock-up on all four wheels occurs simultaneously before releasing control back to the ABS units. Other sensors will come into play if they already think you have lost control of the vehicle.
This is an example of modifying cars and getting into the area that the OEM engineers have not considered possible and getting undesired experiences as a result of the mods.
Thanks for sharing.
Cheers,
Alf.
 
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Discussion Starter · #3 · (Edited)
More about this:

 

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I've read about this on many cars over the past 10-15 years. I don't have the equipment (tires, brakes) to make something like that happen on the 4C. However, I've never experienced it with any of my other cars in the past. It might come down to how each individual driver applies the brakes, but some drivers who have been owners of the same vehicles I owned at the same time mentioned experiencing ICE mode where as I had not. Granted, it's possible I did and just modulated the brake pedal without thinking through it. Sometimes I react without really thinking through why I did what I did on the track. :oops: I always tell my students I do what my car is telling me to do. ;)

On my track prepared cars, I do go for a brake pad with a pretty harsh initial bite.
 

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The voice of inexperience here - despite my poor braking technique, I've never experienced this, but I don't use as aggressive a pad as you do.

I would think that left foot braking would allow for a more modulated application of the left pedal, though. And you can also avoid invoking RAB ("Ready Alert Braking", or "pre-fill" as it is sometimes referred to) that way. That system, along with high initial bite pads, is bound to cause the most severe ABS reaction. By using your left foot, you can stay in the gas a fraction longer that if you were to take off your right foot to move it over to the gas. That ought to afford one time to apply the brake pedal with a bit more finesse, and not rapidly lift before braking to initiate the prefill.

Just a thought for the discussion - not meant as any criticism, as I'm obviously not qualified to go there!
 

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Discussion Starter · #7 · (Edited)
What car?

I thought the ABS sensor either works or doesn't, not that it change its sampling rate due to age?

P.S.: On my way home today I stomped the brakes on the road a few times as hard as I could and I could feel the ABS kicking in, but the car was stopping as it is supposed to, except the ABS intervening to prevent tire lock. What I was experiencing yesterday on a track was different. Not the brake fade, not the ABS interruption, but extreme braking power cut if I can say so. I'm sure it's the "ICE" mode although it's just a phrase. Something is messing up the ABS unit.
 

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The sensor output is either on or off, but its ability to change states(from on to off and off to on) is what degrades after time and it only comes out at high wheel speed.

You don't just have ABS active you also have stability control, and the wheel sensors are the eyes of both those closed loop systems.
 

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I think it can also be exacerbated by the car getting unweighted ie from a crest or dip on the track at the same time. There’s a few bits of Nurburgring notorious for it where the breaking zone is on the brow of a hill so the car thinks you’ve hit a patch of ice or similar and massively reduces the braking force to stop lock up.
 

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@GMS - I haven't run THAT many pads on track, but I have run a few different versions. Specifically Ferodo DS2500, PFC-07 (front), PFC-12 (Front & Rear) and PFC-13 (front & rear). I have triggered the ABS LOTS on track (too much, to be honest), but my track, tires, and setup does not result in massive braking G forces before triggering the ABS. The Lotus are the most notorious for this "ICE Mode" on track, but I have never personally experienced it with the 4C. Now having said that, the PFC-12 and the PFC-13 which I have used the most (with your rotors too) are more of an "Endurance" type pad with moderate initial bite. These typically last about 1 year on my normal track.

So having said all of this... I would note that I have never triggered the "ICE MODE" with the OEM rotors, Giro Rotors, or with your rotors. However, with the larger rotors (and SS lines) my brakes are VERY firm and I need to be careful with my modulation to not trigger the ABS. WAY WAY WAY more firm/stiff than the stock car.
 
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Hello fellas,

Had some track testing this weekend and had some issues with the brakes. It has happened to me before and it is known as "ABS ICE mode". A common issue on Porsche and Lotus if you google it a bit. I've just recently started to explore this so take the posted info below with a bit of reserve.

So what the ABS ICE mode is?

It's not brake fade due to temp or spongy pedal. Its' a very unpleasant situation when you stomp on the brake pedal and the stopping power just isn't there. The brake pedal gets very stiff and the brake force is very weak. Stopping power is greatly reduced and you usually end going straight in to the corner or even out of the track. It's the issue of ABS thinking the wheels are locked but they are not. Releasing the brakes briefly and then reapplying them again fixes this, but driving on the limit we all know there is no such thing as enough time or space to release and reapply brakes again without missing the apex or even staying on the track.

What triggers it? Overly aggressive brake pads (high initial bite) in combination with foot stomping (sudden, hard step on the brake) is my guess so far. I hadn't had this issues until I started moving up the brake pad range with very high initial bite (high coefficient of friction) and started using left foot braking, where it's much easier to stomp the pedal than by using the right foot which due to the position on the accelerator has to move left and it's angled so the force is not as abrupt as with the left foot. It happens on BBK, standard size discs and OEM discs, so the disc are not the issues.

I experienced this before on Winmax W7 brake pads (high initial bite) and it got worse this time with WN3 (highest initial bite). More progressive applying of the brake pedal force completely eliminates this issue and the car stops amazingly. But stomping on a brake it messes the ABS big time and it makes the car virtually brakeless. It could be the yaw angle sensor, or wheel speed sensor, telling the ABS that the car has exceeded the grip levels. I'm not sure. it's something you probably won't experience on a stock car as the tire grip is not sufficient, neither is the brake pad initial bite.

I'll go for less aggressive front brake pads, while still keeping high friction rears, to see how it changes the effect on the brakes and report back.

Anyone else experienced this?
I get that with my 147 if I’m very sudden with the brake application. A little slower squeeze and all is fine. It pays to keep a good distance from the car in front. I haven’t hit anything yet and am glad it steers pretty well.
 

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My most aggressive track days to date has been at Watkins Glen in 2017 with Chin Track Days. Chin is known for their more than usual high performance cars with track setup and honor system safe passing. I only mention this as the mildly surreal garage of participating cars and the spirit of the weekend only encourages you to safely push a little harder with longer sessions.

i was running SS lines, motul660, Girodiscs and Raybestos ST45s where my seasoned instructor was very impressed with the car’s (with a little bit of help from me) cornering and more notably, its braking. I have also run very hard at MidOhio with the same set up several times as that is my home course 30 minutes away without any ICE incident.

I don’ know what friction coefficient your pads were but the ST45s, although not the most aggressive among the Raybestos pads, are pretty aggressive (and great!).



 

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Not with the 4C, but I've triggered Ice Mode with my 370z
For me it was pad compound was too aggressive for my tires, added with the fact that sometimes I brake a little too "jabby", it triggered ice mode more than I wanted to. I ended up getting crappier pads and better tires, and also eased into the brakes a bit more especially when first starting the braking'

For the 370z at least, overly sensitive ABS is definitely partially to blame, I'm not sure how good the ABS on the 4C is when it comes to that regard
 

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unidirectional valve of the power brake can show same symptom.
those valves get intermitent stuck due oil and dirt
not sure if this is the valve

power brake booster.jpg
 

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Discussion Starter · #15 · (Edited)
I was super aggressive with brakes, I admit stomping the brakes instead of progressively adding pedal force, but still, what bothers me big time is that if I stab the brakes too hard, the wheels should lock and ABS should interfere so I would naturally act and bleed of some brake pedal pressure. That's what it happens when you have a very aggressive brake pads, messed brake bias, bad tires, low grip surface, wrong tire diameters or braking with one of the wheel in the air or being unweighted. The wheels keep locking and triggering the ABS, which is perfectly understandable and acceptable.

At so called "ICE" mode, the brakes just act like they are super weak and you try to panic brake and push the pedal even more. It's not about activating the ABS like mentioned up above. The "ICE" mode feels like limiting the brake caliper force. It feels like you need to add more braking power, even though you are forcing the brake pedal to extreme. What I think it happens is that ABS is closing some of the brake line valves and therefore the pressure gets generated between the brake pedal line an the ABS unit, making the pedal super stiff, while afterward the ABS unit and the brake caliper there is a very low brake pressure, therefore the stopping power isn't there and that is something I cannot understand how it's even allowed to happen. I have never experienced this on a street, as the ABS is always flashing if I brake to aggressively, on the track it has happened to me quite a few times and far too many times recently to drive confidently. I'll mount the GoPro to capture the dash next time, to see whether the ABS light flashes at this situation or not, but I can assure you that the brake pedal doesn't feel even remotely the same as it does when the ABS is doing it's work. There are no vibrations, no weird sounds, just no stopping power. Kind of like an extreme brake fade, but without spongy brake pedal, excessive pedal travel. I know that less abrupt application of brake pedal force solves this, but it shouldn't happen in the first place at all. I want the wheels to lock or ABS bleed of the extra pressure, which would still stop the car, but in this case, the stopping power just isn't there. Just no stopping power. Perhaps some 30%. I wish someone with more ABS knowledge than me could explain why this effect happens and what it actually does so I could understand it.

My brake pads currently are WN3 (0.55 cf) and that is a high friction and high initial bite pad. The mentioned above Raybestos ST45 have only 0.40 cf, which is somewhat low-medium friction and initial bite pad, with a comparable initial bite level as Ferodo DS2500 has, but the following has low temperature resistance so the cf falls with temperature rising. While brake pads selection will affect the ABS, still an effect like mentioned above the so called "ICE" mode is something shouldn't be happening if you ask me.

Here are is onboard on how it looks. This was the first time this started happening to me. Higher cf brake pads and left foot braking. You can see that ABS light hasn't triggered in first case and it triggered in second case only when I already almost came to a full stop and regained stopping power. I wasn't paying much attention to it at that point, and had raced entire season by being a bit less "stompy" on the brakes. Sure I can brake less aggressive and not trigger the "ICE" mode but I would prefer if this wouldn't be happening at all.

.
 

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For your use case, I think you want to start looking at something more race capable. Most folks in the circles I run, when they have turned their car into a mostly or completely dedicated track car, they typically will remove the OEM ABS and TC mechanisms and go with something more race focused (if their class allows).
 

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Were you lifting abruptly at exactly the same time as "stomping" on the brakes (i.e. same millisecond)? With left foot braking it's possible to do.
Lifting abruptly does initiate RAB ("prefill").
I wonder if that process somehow interfered with your initial brake pedal application? If so, then this problem is not with the ABS at all, but rather an open valve that the brake pressure was diverted out instead of RAB prefilling the calipers that way - or however that system actually works)???
RAB is probably based on the time delay from lifting off the gas rapidly, to using your right foot on the brake pedal.

Just another theory... No idea if it could be possible, though.
 
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