I drive an Audi Quattro. During the dismantling of the summer bikes in autumn last year, I had between 4.5 and 5.0 mm in the front and between 6.0 and 6.5 mm in the rear. Unfortunately, I had a nail in the rear side of the tyre. The tyre had to be replaced. When I was assembled a few weeks ago, I changed the rear wheels forward and the front wheels backwards. The car runs perfectly and without any influence on the steering wheel. I imagine that there is a slight, speed-dependent surrene on the front axle. However, I can’t detect a defect on one of the tyres. Therefore, I wrote today to the tyre manufacturer, who answered promptly. He explained that there should be no differences in the profile depth of more than 1 mm on an all-wheel drive vehicle. With all tyres among themselves! And that the noises I perceived from the uneven profile depths So after a season I always have 1 to 2 mm difference between the tyres of the front axle to the rear axle. Since there was never any such perceptions in this regard, I can’t understand the explanation of the tyre manufacturer within a vehicle axle. Would a defective tyre always mean the replacement of one or even three more tyres?