Match the same axle tires within 4/32's of an inch over tire circumference. More than that can damage the differentional over time. If you wear a tire down more than 4/32's of an inch and then put a new tire on the same axle with it, the diff will need to make up the tire rotational difference. To picture this, imagine running on a space saver tire for hundreds or thousands of miles. This rule applies to any vehicle. If your orginal tires are wore more than 4/32 and one blows, you have to replace the opposing tire on the same axle if it is worn down more than 4/32.
Fleetwood Providence 2008 40e
Ford F-350 4x4 Diesel 6.0L 2006
Honda CR-V 2006