Tire size, what does the first number mean?

Question

Like a 245 50 16

What does the 245 mean? I thought it was width. Is that right?

Do the tires I take off have to match my new tires?

Answer 1

that,s how wide the tire is. you can have different tread but it has to be the same size.

Answer 2

245 is the width in millimeters. The next number, 50, is the aspect ratio defining height. It means the height is 50% 0f 245. The final number is the rim size. The new tires don't necessarily have to match. If you're changing all 4, you can go up or down a size or two. If it's a four wheel drive vehicle, just make sure all four are the same size. A two wheel drive truck can have bigger tires on the back if that's the look your going for.