Braking problem - malfunctioning ABS

wstar

It's a complex issue for sure. The bottom line seems to be that the best way to trigger ice mode is to have 1-2 wheels lock up, even for a split second, when the other wheels are still spinning and have a good margin of traction just based on speed sensor inputs and whatnot. Depending on suspension and brake config, usually what ends up happening is you're getting one or both rear wheels to momentarily lock up while the front still has grip left, and that pushes it into ice mode.

The rear has that tendency to "artificially" lock up early because the stock rear calipers are just a bit oversized compared to what they really need to be, and depending on your suspension config the rear can also be a little "skippy"... by which I mean if there's ripples in the pavement under braking, the suspension might let a rear tire catch air for a split second, during which time it immediately locks up and triggers ice-mode. Hell even if the rear tire doesn't actually get free of the pavement, just the suspension response to the ripple could unload enough weight from one or both rear tires to let them lock up faster.

Biasing the brakes via pad choice definitely helps - weaken the rear pad's bite and it's less likely to do the above under heavy braking. Softening the swaybar in the rear (e.g. go less-stiff on the Hotchkis settings) can make the rear maintain better traction under braking on an uneven surface as well. Of course all this about the rear is what most of us seem to experience, but someone's car could be producing ice-mode in a totally different way (e.g. via front lockup) if their suspension/brake setup is unusual and different.

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