Traction
 

My old 85 500sel runs perfectly but is hopeless on wet streets (and snow) when trying to pull away from a stop or even when getting up a hill. The tires are ok -Goodyear touring . Will additional weight help. I always keep the tank full in bad weather.
Any thoughts would be well received

If you routinely see snow you need 4 good winter tires. I got mine from Tire Rack, mounted on MB replica wheels. I have used Michelin Arctic Alpins, which are OK, but have heard great things about Nokian NRWs, so I plan to replace mine with those.

Check out the "wheel and tire" section of this site for more info.

Just last week i took off my summer wheels (Fulda Extremo) and put on my winter wheels (Nokian NRW).

In snow the Nokians are pretty good, though i wouldn't call them excellent. But on wet and rainy roads them Nokians slip and slide way more than the Fuldas did.
Maybe the Nokians are only good when it's freezing?

Freestyler