WHILE DRIVING HOME FROM WORK AT ABOUT 12 AM IN THE RIGHT HAND LANE ON HIGHWAY 217 IN TIGARD OREGON, JUST PASSED EXIT 4 MY STEERING STARTED PULLING ME TO THE RIGHT SIDE OF THE ROAD, TOWARDS THE GUARD RAIL. (WAS TRAVELING AT APPROX. 55 MPH) I TRIED TO CORRECT BY PULLING THE STEERING WHEEL LEFT, BUT THE VEHICLE WOULD NOT RESPOND. I THEN HEAR A VERY LOUD SNAPPING/BREAKING NOISE UNDER MY LEFT FOOT AND THE NEXT THING I KNOW MY CAR SLIDES TO THE RIGHT HAND SIDE, INTO THE GUARD RAIL. I THEN BOUNCED OFF OF THE GUARD RAIL AND THE CAR CONTINUED SLIDING/SPINNING UNTIL COMING TO REST IN THE LEFT HAND LANE. TIGARD POLICE ARRIVED AT THE SCENE AND STATED THAT IT LOOKED LIKE THE "SUSPENSION BROKE AND THE WHEEL FELL OFF", CAUSING THE WRECK. THERE WAS SUBSTANTIAL DAMAGE TO THE FRONT END (LEFT SIDE) AND MARKS ON THE REAR BUMPER. WITNESS FOLLOWING BEHIND ME STATED THAT THEY SAW ME DRIVING IN FRONT OF THEM AND THEN ALL OF A SUDDEN THE CAR STARTED SPINNING, APPARENTLY FOR NO REASON SINCE THERE WAS NO IMPACT. *NM