Clicks audible in rear wheels
I nearly always hear loud clicking--commensurate with the velocity--in my rear wheels from standstill to 30 m.p.h. acceleration. It started recently, about 2 months ago. My mechanic, whom I've since left because of a lot of bad work he did (e.g., returning 3 times for the same repair; breaking my brand new horn twice upon installation on a brand new steering wheel then gluing it on!; taking 4 weeks after I drop off my car for a simple repair, etc., etc.) told me it was because of "rocks" caught in my treads. Sounds like a lot of baloney to me in light of his shoddy work. Is it true?