# NHTSA Engineering Analysis EA84026
> **REAR BRAKE LOCKUP** · Opened 1984-08-15 · Closed 1988-04-08
## Investigation
- **Action number:** EA84026
- **Type:** Engineering Analysis
- **Open date:** 1984-08-15
- **Close date:** 1988-04-08
- **Manufacturer:** —
- **Affected makes:** —
- **Affected components:** —
- **Affected model years:** —
- **Affected (make, year) variants:** 1
## Summary

SUMMARY: THE REAR CYLINDER DIAMETER WAS REDUCED FOR 1984 MODELS TO IMPROVEBRAKING BALANCE FOR EMPTY VEHICLES.GM CLAIMS REAR BRAKES CAN BE LOCKEDON MOST EMPTY PICKUPS ON LOW TRACTION SURFACES.ANALYSIS:PICKUP TRUCKS TRADITIONALLY HAVE BEEN DESIGNED WITH BRAKINGSYSTEMS WHICH CAUSED THE REAR BRAKES TO LOCK FIRST WHEN THE CARGO BED ISEMPTY, SO THAT MAXIMUM EFFECTIVE BRAKING IS AVAILABLE WHEN A LOAD ISPRESENT. MOST MODERN LIGHT TRUCKS AND VANS UTILIZE WEIGHT SENSITIVE PROP-ORTIONING VALVES TO PROVIDE GOOD BRAKING AT ALL LOADS.STATUS:C-MEMO MAY NEED REVISION.IN FINAL BY 12/31/87.===

## Source
- [NHTSA ODI investigation page](https://www-odi.nhtsa.dot.gov/owners/SearchResults?searchType=ID&targetCategory=I&searchCriteria.nhtsa_ids=EA84026)
---
*AI Analytics · CC0 1.0*