usage of snow chain button

[DuckMuck]

Hello,

I have a Canadian '95 E420, and on my center dash, there is a button for snow chain. I've never had the need to use the button, and was curious as to what it exactly does. The manual very vaguely states that it "increases traction"...and also mentions that if your car is equipped with ASR, the button MUST be depressed if you are to be using snow chains. I was wondering if that snow chain button actual deactivates ASR, since I can't see how the jerky movements caused by ASR could be helpful if one has snow chains on. I've always wanted to test it out when I was at home, but it keeps slipping my mind. Any bits and pieces of information would be appreciated. Thank you!

[Michael]

This button allows a greater amount of differentiation in rotational speed between the front and rear tires. ASR takes its cue from the front wheels; how fast they're turning is approximately how fast the rears should be. However, when tires become clumped with snow, their rotational speed varies to such a degree that the ASR will actually keep you from moving. Same thing when they have chains on, if the chains load up with snow.

I've actually had this happen in a snowstorm; hitting the button allowed enough wheelspin to get me going again. In my case, the rear end just stepped out to one side, and the car allowed a sort of power slide...very controlled.

If it weren't for this feature, I'd have replaced the button with a defeat switch long ago. But then again, I know how to disable ASR when I want to

Hope this helps