Tires: diffrent tread paterns, emergency maneuvers, size tires

Question
i have one of those "i know everything" bosses. well one of the guys at my work just got a used truck and is looking for just 2 tires for the winter.now his truck is only 2wd not 4wd.my boss told him he cant buy just 2 tires he has to buy 4 tires because with some vehicles if you put a different tread pasterns on the back than the front it will mess up the computer and throw off the spedo. i told him thats not true tread pattern wont do that only different size tires from what is suppose to be on the trick will throw off the spedo . my question is will having different tread pasterns on the back from the front cause any problems if the tires are all the same size?

Answer
Douglas,

Your boss has a point: Differences in tires - front to rear - could cause the vehicle to behave unpredictably during emergency maneuvers.  It's always best to have 4 identical tires - same brand, model and state of wear - to ensure the vehicle behaves predictably in all conditions - as best it can.

However, there is no guarantee that different tires - even though they are the same size - are indeed the same diameter.  There could be some differences in diameter.  This is why it is imperative that AWD and 4X4's have the same exact tires front to rear. But it is not critical for a 2WD.

So in some respects your boss has wrong about the NECESSITY of 4 identical tires, but it is a good idea.