Feels like I've been here before

[JST]

Originally Posted by clyde

In a normal ABS engagement on dry pavement, the brake pedal chatters as you push the pedal and the pedal pushes back with variable resistance as each wheel goes through a lock-release cycle. The vehicle slows throughout the ABS engagement as a result of the brake application.

The "ice mode" behavior I'm referring to is a fully stiff brake pedal without chatter while the vehicle does not lose any velocity from brake application because the ABS system is preventing the brake pads from being applied to the rotors. The reason it's called "ice mode" is because it's the behavior that occurs when you try to apply the brakes while on a sheet of ice.

In an autocross situation, we often have cars behaving outside normal behaviors. We'll often be at full throttle with a significant and rapidly transitioning lateral load followed in an instant by full brakes and a sharp steering input in the opposite direction of the lateral load transfer.

In normal street driving—even track driving—that situation strongly correlates to something bad happening. What the ABS calibration sees is something it interprets kind of like a driver over-correcting a fishtailing situation AND simultaneously jumping on the brakes which is highly likely to lead to a total loss of control and very worse things happening. In response, the ABS prevents brake application so the driver doesn't lose steering input.

When it happens, you basically have three choices. You can stand on the brake and wait it out for a predetermined amount of time (specific to the ABS calibration, but typically 1-2 full seconds) for the pedal to return to normal. Or you can lift off the brakes and immediately get back on them. The time it takes to release and reapply the brakes, the out-of-envelope conditions that caused the event will have dissipated to the point they're back within the envelope for normal braking operation. The third choice is to lift and just chuck it even harder into the turn you tried braking for. That last choice is often the least damaging to your course time, but it's never as good as it would have been without getting into the event.

When you walk an autocross course before driving it, with a little experience, you can see where it's going to happen.

So, while the conditions triggering the behavior are different, the resulting behavior is the same. Because autocrossers are simple people and we're describing the behavior rather than the conditions that triggered the behavior, we call both of those "ice mode." Except our GM engineer friends. They flip their shit when call the second situation "ice mode" because it's not. Even though it is. But anyway...

Like Nick said, it's not a new thing. The ice mode in icy conditions has existed in ABS (or similar) equipped cars since the 70s. The self-induced ice mode that I'm complaining about...I don't know how far back it dates. The oldest cars I'm aware of where it's an issue in autocross are both MY2002 cars (350Z and Corvette Z06).

In the past few years, it's been noted to be present on larger numbers of cars, but even where it's present, it can range from "yeah, it happens, but it's nothing to be concerned about," to "Fuck this! I know it's only been one event, but I'm selling the car."

Tying this back to the 6G Camaro... The regular 2016-2018 SS Camaros are hurt pretty badly by the self-induced ice mode. I know more than a couple people that reluctantly sold theirs because of it. Non-1LE SS Camaros with MRC shocks may be very slightly less prone to it, but no non-GM employees/suppliers are sure. 2017/18 (there was no 16 model) SS 1LEs have a different ABS calibration that is less prone, but it's still an issue.

For 2019, all 6G Camaros got new ABS calibrations that "fix" it. A few of the people I know who sold pre-fix SS Camaros now have 2019/20 SS Camaros and are very happy with they now have.

For reference, my 2017 turbo Camaro suffers from it, too, but it's not highly debilitating like the SS cars. I would have an ice mode experience once every few events, usually in connection with a fuck up. My co-driver would have at least one experience with it at almost every event.

That sounds frustrating as hell. It would probably keep me from buying anything pre-2019.