Haldex / Meritor / Bendix Drum Brakes (foundation)
Multiple (Haldex, Meritor, Bendix) · Brakes · Drum brakes (foundation)
What this component does
S-cam drum brakes are the traditional foundation brake type for Class 6-8 commercial trucks — used for over 50 years, still dominant in vocational and budget highway specs. The S-cam is an S-shaped lever that rotates to push brake shoes outward against the drum. Slack adjusters (now automatic on modern trucks) maintain proper clearance. Drum brakes are cheaper than air-disc and pads (shoes) last longer (350-500K miles vs 250-400K for ADB pads). Disadvantage: longer stopping distance, brake fade under repeated heavy use.
Specifications
- Manufacturer
- Multiple (Haldex, Meritor, Bendix)
- Category
- Brakes
- Subtype
- Drum brakes (foundation)
- Truck class
- Class 6-8
- Production
- 1980–present
- Applications
- Most Class 6-8 vocational + budget highway specs
Design and engineering
Brake drum on the axle hub. S-cam shaft rotates via air-actuated brake chamber. S-cam pushes two brake shoes outward against the drum's inner surface. Automatic slack adjusters maintain shoe-to-drum clearance.
Generations
- S-cam drums (1980–present)Long production run across multiple suppliers. Automatic slack adjusters became standard mid-1990s.
Reliability and longevity
Bulletproof reliability when maintained. Brake shoes are inexpensive ($50-100/set) and easy to replace.
Common problems
Brake fade under repeated heavy braking (mountain descents). Slack adjuster wear if not lubricated. Drum cracking in extreme heat. S-cam bushings at 500K+ miles.
Maintenance schedule
Brake adjustment check every PM (50K). Slack adjuster lubrication every 100K. Shoe replacement every 350K-500K miles.
Pros and cons
Pros
- ✓Cheapest brake option
- ✓Long shoe life (350-500K)
- ✓Simple, well-understood technology
- ✓Universal parts availability
Cons
- !Longer stopping distance vs air-disc
- !Brake fade in repeated heavy braking
- !More service-complex (slack adjustment, etc.)
- !Heavier than air-disc
Trucks that use this component
Related DTC codes
Other Brakes components
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- Bendix ADB22X / ADB22X-V (air disc brakes)Bendix Commercial Vehicle Systems
- Haldex EBS (electronic braking system, trailer-focused)Haldex (now part of SAF-Holland)
- WABCO OnLane (lane keep + collision)WABCO (now ZF Aftermarket)