Is it safe to replace a single tire on the front axle and if yes should the new tire be moved to the back? We replaced a front right tire, after picking up a screw. Now we hear that it's not safe to replace a single tire on the same axle.
First rule of tires: Tires with the deepest tread go on the rear.
Second rule of tires: On vehicles with All Wheel Drive (AWD) tread depths are not to vary by more than 2/32".
Rule one is required because vehicle control can be lost if the rear tires hydroplane before the front tires. Rule two is required by most manufactures of AWD gear because the equalizing clutch unit can be damaged if the tires outside diameter varies too much.
Having a tire of larger diameter on one side of an axle is generally OK because the differential unit is designed to compensate.
Keep in mind the principal that the tire with the shallowest tread depth will hydroplane first on a wet road. This breaks grip and can cause loss of control.
Ideally all the tires on a vehicle will be rotated in such a way that tread depths will be kept close together.
For optimal braking traction and reduced loss of control due to hydroplaning replace tires worn to 4/32" tread depth remaining.