Originally Posted by dan_vector

So rear track width effects the lateral weight transfer and so if you narrow the rear track you reduce the amount of lateral rear traction you have. Therefore increasing steering generally but at a cost of stability. To be honest on the 977 Viper I don't really change the rear track width and run it consistently at 263mm. The Behaviour is no different to a car with a diff. A track width adjustment also changes the roll centre slightly but in 1/8 onroad I don't really change the rear track width very often.

Rear Toe-in. Basically the more static rear Toe-in you run then the car will have less steering generally. The reverse is true. The greater Toe-in also generates more lateral rear grip hence less steering and so as you reduce the toe in the lateral rear grip decreases so you get more steering but less stability and perhaps the car generating oversteer situations. I generally start with 3 degrees and then reduce it towards 2.5 degrees as the traction of the track increases.