Car: 2000 BMW 740i
Join Date: 28th August 2009
Thanked 103 Times in 42 Posts
VSA on snow, dangerous?
So we just got about 30 cm of nice fresh snow where i live, and the plows where a bit slow on getting all the roads clear. Since i have never tested my CTR on this kind of surface i took it out for a short trip of about 12 km to see how it was.
As i said the roads are snow covered, and for the most part not been cleared yet. This lead to some rather unstable conditions when other cars had gone before me. On the slow parts, 50-60 km/h, it was ok. Was driving with VSA on. Anti-spin was a bit to quick to take control, but nothing major.
The dangerous, and what scared me, was when i got out on a pretty straight road where the speed limit is 80 km/h. Same road conditions, nice powder that other cars have driven on. When i got up to some speed, somewhere between 60 and 75 i started to notice a slight pendulum effect in the rear of the car. I slowed down to 40-50 but it continued and increased over time. As soon as i turned the VSA off the car straightened out again and i got much more control.
What i think happened was that the rear shifted slightly in its tracks due to the tracks left of other cars in front of me. Then the VSA picked this up and tried to compensate. Because of the slippery conditions the car started going the other way and the VSA compensated again, leading to a pendulum effect in the rear. Does this sound plausible?
It put a bit of a scare in me seeing that slowing down had no effect, but that turning the VSA off did. I'm considering driving with it off now as long as im not just driving slowly in the city.
Edit: Just to clarify, i have proper winter tyres, Nokian Hakkapelitta without spikes on original 18" rims, 55/225.