Tire clearance

A bias tire folds. A radial tire the belt moves as one. So if the radial tire at the road surface moves over 1/2" the side at the spring moves with it.
A 1/4" space for movement would be OK for the street. For hard corners on a sticky track add a 1/4" - 3/8" spacer behind the wheel to keep the tire off the spring. Good radials don't have much of a side wall thickness