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Originally Posted by Kuan
My feeling is that almost every emergency situation starts with a foot on the brakes anyway. So once ABS kicks in, the driver then has a natural tendency to try and steer the vehicle out of trouble. I guess ESP is beneficial in the Moose avoidance maneuver but that's about the only type of maneuver in which I find that ESP would work better than plain old braking and steering.
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Not to be argumentative, but brakes are not always the first step in an emergency. Steering is often the first. Steering and braking is also a high probability. With ESP both of these work better than ABS and the driver alone, left with turning the wheel while his brake pedal buzzes.
The reason is when you brake hard and steer the car will respond to the maximum extent the front tires can maintain a grip. Typically this results in understeer and the car turns in the direction of the driver input, but not at the same rate as he was expecting, which leads to more steering input and more understeer. ESP modulates the front and rear brakes in a sequence, based on steering input and braking pressure, as well as what the car is actually doing in response. The net result is the car ESP system eeks out additional steering performance while continuing to slow the car down at the maximum practical rate.
The system also comes into play when the car might have begun to oversteer due to poor driving surfaces, road undulations and curves, or driver input that just causes oversteer. In an oversteering situation brakes are not likely to be a good choice. ESP responds by preventing oversteer before the driver gets sideways.
All this is up to a limit of course. After the limit I suppose the car will still under or over steer out of control. The fact you are driving over your limit is identified by a warning signal on the instrument panel whenever the ESP system is activated. The gist of the message is "I just saved your butt, and you better regain control or I may not be able to help the next time."
The Moose Avoidance Test benefit attributed to ESP is a consequence of ESP preventing uncontrolled over and under steering that leads to roll overs, which then prevents roll overs. It is more a "side effect" of ESP, not the primary goal of the system. Jim
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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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