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by bradleyland 5444 days ago
I'm not sure I'll be able to change your mind about this, but I'd like to express my opinion on your sentiment and leave it at that.

I think that maybe you're wrong about a few things here. First and foremost, that your slide was recoverable.

I'm a car guy myself. Like you, I insist on manual transmissions with rear wheel drive. I've been to driving schools, read extensively about how suspension affects handling dynamics, and turned a few wrenches in my time. Even with all that, I try to remain humble about my own driving abilities and the fact that while I enjoy it, I don't drive professionally, so I shouldn't expect professional results.

Your comments about skid recovery apply to the input controls that are available to you as the driver. They don't apply to the input controls available to the traction control systems in your car. For every subtle detail that you learned about handling using the steering wheel, brake, and clutch, there are equivalents for the systems available to the traction control system, such as individual wheel braking.

Stopping a slide is about controlling rotation. You cannot use the brake to directly rotate the vehicle because you only get one brake pedal. The best use of that brake pedal, as a driver, is in controlling the speed and weight distribution of the automobile. That is the most you can hope for.

"My issue with Mercedes's Traction Control in particular isn't even that it makes drivers lazy. It's that in at least that situation, it can't tell the difference between power-induced oversteer and breaking-induced oversteer. In that situation, it reacted EXACTLY WRONG. It doesn't matter whether the driver is competent or not if the system makes the opposite changes that it should."

The stability program in a Mercedes absolutely knows the difference between power-induced oversteer and braking-induced oversteer. It uses accelerometers, yaw sensors, throttle position sensors, and individual wheel speed sensors to infer your intended direction of travel. Braking the outside rear wheel does transfer weight forward, but it has a far more significant positive effect on correcting rotation because of the asymmetrical application of braking force. Your slide was simply unrecoverable. You think that it was recoverable, but you'll never know for sure. Based on the physics involved, I think you're wrong.

I've tested the limits of these systems myself. My 2006 GTI had ESP. I took it out to a dirt road and explored the limits under slalom conditions and hard turns. These systems are amazing at recovering slides that can be recovered. If I pushed hard enough, I could "break through" to an uncontrollable slide, however. When you "overshoot" your mark, brake, turn, then hit a rumble strip (which significantly reduces available traction) you end up in an unrecoverable slide.

The irony here is that your Mercedes' ESP system didn't almost kill you, you did.

2 comments

Thanks for offering your opinion. While I want to respect the GP's personal experience, your comments echo my feelings. My favorite part of a Mercedes (and this is surely true for other premier makes) is that everything seems to have been thought out and engineered ^1. And with my own personal experience of the cars TCS, I felt it very hard to believe that the Mercedes TCS would be so simplistic.

^1 Not to say I don't have my issues with the cars -- stuff like a crappy Chinese made iPod interface.

Edit: That video is stunning. Thanks for the share.

I'd strongly encourage you to take advantage of any driving school that Mercedes offers. I've read countless messages from individuals who insist that these safety systems (ABS, TCS, and ESP) are a detriment to their ability to drive the car, but I've experienced them in two makes of automobile (VW and BWM) now, and I now know from first-hand experience that they work fantastic. There is no replacement for testing them out for yourself.
To support my point, here is a video of Tiff Needell testing an older version of ESP in a Jaguar on a sheet of ice. The ability of the system to stop a car from sliding out of control under these conditions is just mind boggling.

This 6:21 start point shows both (with/without) tests:

http://www.youtube.com/watch?v=j-hHWSQhKuc&feature=fvwre...