THE PLT LANDED ON A RURAL ROAD, DUE TO UNSUITABLE TERRAIN CONDITIONS ON THE SOD FIELD WHERE HE HAD INTENDED TO LAND. DURING THE LDG, THE AIRPLANE VEERED OFF THE LEFT SIDE OF THE ROAD INTO A DTICH. THE PLT REPORTED THAT DURING THE ROLLOUT, THE RT BRAKE BEGAN TO FAIL AND THE AIRPLANE BEGAN TO VEER SLOWLY TO THE LEFT. THE PLT STATED THAT HE ATTEMPTED TO CORRECT THE VEERING BY RELEASING THE LEFT BRAKE AND APPLYING RIGHT RUDDER/TAILWHEEL STEERING. THE AIRPLANE CONTINUED TO VEER LEFT, HOWEVER, AND ROLLED INTO THE DITCH. THE PLT ATTRIBUTED THE RT BRAKE FAILURE TO BRAKE ADJUSTMENT PROBLEMS; HE INDICATED THAT THE RT BRAKE HAD A HISTORY OF ADJUSTMENT PROBLEMS COMPARED TO THE LT BRAKE, AND REQUIRED PERIODIC ADJUSTMENT. THE PLT DID NOT REPORT FINDING ANY OBVIOUS MECHANICAL FAILURES DURING HIS POST-CRASH EXAMINATION OF THE AIRPLANE. ACCORDING TO AIRPLANE MAINTENANCE RECORDS, THE CABLE-OPERATED BRAKE SYSTEM WAS REPAIRED DURING THE LAST ANNUAL INSPECTION, ABOUT 4 MONTHS EARLIER.