EA87009 · EA
SERVICE BRAKES, HYDRAULIC Investigation
ANALYSIS: THE PROPOSED GM CHANGES SHOULD REDUCE THE FRONT-BIAS IN THEREAR BRAKE SYSTEM.HOWEVER THERE IS NO INDICATION THAT GM WILL RETROFITTHE 1985 AND 1986 MODEL YEAR VEHICLES.REPORTS INDICATE THAT THE PROBLEMMAY NOT LIE IN THE BRAKE BIASING SYSTEM, BUT RATHER IN MALFUNCTIONINGOR IMPROPERLY DESIGNED REAR BRAKE ADJUSTERS.STATUS: ANALYZING RESPONSE FROM GM DATED 5/12/87.AWAITING REPLY FROM NHTSA'S LEGAL STAFF CONCERNING GM'S RESPONSE.TOLD TO SIT ON IT A WHILE BY MR. PARKER AT 8/20/87 BRIEFING.AFTER LEGAL'S REPLY, THE DATA WILL BE UPDATED AND AN ACTIONDECISION WILL BE FORWARDED FOR SUPERVISOR'S REVIEW.===
PE86053 · PE
SERVICE BRAKES, HYDRAULIC Investigation
SUMMARY OF INFORMATION FROM MANUFACTURER:NO TSB'S OR RECALLS HAVE BEENISSUED ON THIS MATTER.THE 1985 CAMIP PHASE II SURVEY RATED THE GM M-VANBRAKE EFFECTIVENESS LOWEST AMONG VEHICLE LINES TESTED.IN RESPONSE TO THECONCERN OF VAN OWNERS, CHANGES IN THE REAR WHEEL CYLINDER DIAMETER AND THEPROPORTIONING VALVE WERE PLANNED FOR THE 1987 MODEL M-VANS.ANALYSIS:THE PROPOSED MANUFACTURER CHANGES WILL REDUCE THE FRONT-BIAS OFTHE BRAKE SYSTEM.HOWEVER, THERE IS NO INDICATION THAT GM WILL RETROFITTHE 1985 AND 1986 MODELS.OVER THE NINE MONTHS SINCE THE PE WAS OPENED,THE NUMBER OF ODI REPORTS HAS INCREASED BY 300%.THESE REPORTS INDICATETHAT THE PROBLEM MAY NOT BE AN OVERLY FRONT-BIASED BRAKING SYSTEM, BUTTED M-VAN'SBRAKE ADJUSTER WAS NOT OPERATING PROPERLY, ALLOWING THE LEFT REAR WHEEL TOROTATE, EVEN WITH 200 POUNDS APPLIED PEDAL FORCE.THE VEHICLE DID PASSMODIFIED COMPLIANCE TESTS FOR BRAKE STOPPING DISTANCES.PROPOSED ACTION:TO UPGRADE THIS TO AN ENGINEERING ANALYSIS.===