RS2000 wrote:I'm with Spac, thinking that the car should be balanced with old slippery tyres (assuming front & rear tyres are in the same condition).
I wouldn't think putting on new sticky tyres would change the cars balance. Sure there would be more grip, so the understeer would happen at higher cornering speeds. On a wet skid pan, or loose gravel, a good balanced car doesn't suddenly get horrible understeer because there is no grip.
But if you're looking at a solution, knowing what we know, you 'd have to start with tyres and alignment surely?