Just replaced my rear 265/35/21 tires on my S75 rear-drive (with coil springs) a month ago at 25,300 miles. Rears were 2/32" at the wear bars. The original 245/35/21 fronts are holding up at 6/32". Alignment within specs. Since rears are wearing about 2x faster than the fronts, looks like I'll need a full set of tires nearing 50,000 miles. Keep in mind that coil spring cars run about -1.1 to -1.3° rear camber while the air cars run -1.5° to -2.0°. Translation: rear 21s on air cars can wear out faster, especially if set mostly to Low.