Hey guys, think about this for a minute...
Bigger tyres can give you LESS 'grip'.
'Grip' is created by the weight of the car pushing down (gravity) & pushing the rubber tyres against the road.
Your car is a certain weight, sitting on a fixed area of rubber. If you have more area of rubber, there are less pounds of weight per square inch of rubber, ie less 'grip'.
So fitting a narrower tyre gives you MORE pounds of weight per square inch of rubber, ie more 'grip'.
Obviously this doesn't work when you take it to extreemes, your car would not work on bicycle tyres, or road-roller tyres, but what I'm getting at is that you can 'over-tyre' a car.
If you're interested in ultimate speed, then rolling resistance also has to be taken into account....
So bigger isn't necessarily better!!