[CapriRacer]

Conventional wisdom in the tire industry says that the best condition is to have all tires the same size, make, model, and state of wear. That's so the vehicle doesn't behave unpredictably during emergency maneuvers.

Can you violate any of those provisions and still be safe? Yes, but in order to be sure you have to do those emergency maneuvers in controlled conditions and in a suitable location - but that would chew up a set of tires, so if you are going to do this exactly once, it makes no sense to test - but then you are taking a risk, and it could be a big one!

Now what about staggered tire size set ups? Again conventional wisdom is to use the same make, model, and state of wear - with the same proviso if you deviate from that wisdom.

But the extent of the problem is that if you don't test, you will never know until you are confronted with an emergency, and then it is too late.

How bad can this be? I've seen tests where the car was almost undriveable as it approached the limit of adhesion. It would spin out quite violently and quite suddenly. So, Yes! This is a real concern.