Stretch the tyre wall? Not too sure what that means.
At the minute the wheels are about 1/4 of an inch from under the arch (front only) and no rubbing on tyre.
Got about an inch and half clearance from the arch, front and back of each wheel
Nearer to 3 inch's above.
As I said my main concern is when lowerd and turning tyres will rub the arch.
Suppose could buy a cheap set for now and see how it goes, then upgrade if everything seems fine.