Wider wheels and move suspension inward?

[71RS/SS396]

Brian Finch and I did some testing last month and since our cars are essentially the same it was easy to do. He has (had) a 335 front tire and I have a 315. We swapped cars and I notice his car had quite a bit of oversteer on turn in, he was surprised at how much more balanced my car was. We swapped my wheels onto his car and it cured the oversteer with no other changes. Imho there's a point where you have too much front grip and it upsets the balance of the car.