93 Mazda 323-Today was coming down a gradual incline--abt. 30 m.p.h.--had to brake to slow up for bends in road--car started to shake bad.- Heard a noise I thought was fromfront-driverside wheel. When I slowed up to about 5 m.p.h.--shaking would stop---Start to shakeagain as I gained speed.Would hear noiseon turns.--Got it home--took it out twice since (same route) and no shaking and no noise. Had back brake pads replaced 1 month ago, and front brakes checked--mechanic said everything else okay. Put air in the back tires since---Shaking was quite bad and had me really concerned. Any suggestions?