tire width vs under/oversteer

[Majik16106]

posted this on another forum, but all in all you guys seem to know a ton more about this stuff so read on and give your thoughts?

it was always my understanding that the wider the front tires were, the more understeer the car would see, widening the front and rear tires would make the car more stable at speed but it would be a lot harder to get to turn, but another member of this forum told me i was wrong? if i am.. can someone explain to me how a car with reasonable suspension settings, and lets use supra fitments, so 245/40/17 front and 285/45/17 rear tires on 17x8 and 17x10 wheels is more likely to understeer than the same car with 285/45/17 upfront and on the back.