My ancient experience with GII and GIII it was common to have rumble as the nose-wheel was quite small for the usual forward C of G and went out of true quite quickly; we did explore having a balancing rig; usually spinning it on the axle, if no flat spots and if the wheel stopped consistently at one point then a balance weight re-distribution; a repack of grease and torque worked for a while longer. After retraction it should be snubbed but these also had wear and no re lining, though Marshals of Cambridge did devise a repair scheme for this circa mid 1990's.