Even on a front wheel drive?
Always, baby. Here's why.
It's nothing to do with keeping drive traction. It's to do with stopping in what is referred to in SAS jargon as The Worst Case Scenario -- where everything that can be adverse,
is adverse.
You're approaching a corner. It's pissing down after a dry spell, so the roads are not just wet, but greasy wet. Kid jumps put. You jam on the brakes.
At that critical moment, what do you want the car to do? Which wheels do you want to be the first to lock -- the front wheels or the back wheels?
A locked wheel has a weaker grip on the road than a wheel that (under heavy braking) is still rotating.
Suppose you lock the front brakes, and the front wheels start sliding. Now, much of remaining braking force is coming from the rear wheels. This is a a reasonably stable condition. You lose steering, but the car carries on in more or less a straight line.
Bad enough, of course.
But suppose the rear brakes lock first. Now, the remaining braking force is coming from the fronts. This is
unstable, in that the back of the car now wants to overtake the front of the car. So the car spins out -- it (you) could go anywhere -- into the oncoming traffic, anywhere.
It is more dangerious, under heavy braking, to lose control of the back of the car than to lose control of the front of the car. When it comes to it, you want the front wheels to lock first. So put your best tires on the back.
Of course, we should all always drive carefully enough that we're never faced with the need to brake so sharply that we might skid. And on a dry road, you can probably avoid skidding even with bald tires.
Modern cars have anti-skid, and that's good. But the sensors basically measure the rpm of each wheel, and ease off the brake on that wheel if the rpms are slowing too rapidly. The anti-skid system is not very effective in comparing back/front. You should never rely on your anti-skid to protect you
in extremis -- the lower the friction between the road surface and the tires, the lower the effectiveness of the anti-skid.
Replace tires in pairs, keep the pairs together, never 'rotate' the tires, and always put the newest tires on the back. Good stopping is more important than good going.
