I have a 4×4. Do I really need all four tyres replaced?

Often, yes, and it is not an upsell. Permanent four wheel drive systems measure the speed of each wheel, and a new tyre has a bigger rolling circumference than a part worn one, so mixing them makes the differential or the centre coupling work constantly. Some manufacturers will not accept more than a couple of millimetres difference across the axles. If your other three are still deep and the same make and pattern, we will tell you that one or two is fine. Tell us the model when you ring and we will check what it needs. See 4×4 tyres.