Charlotte Mobile Diesel provides air brake repair through local mobile technicians who also cover trailer repair, DOT inspection prep, roadside service and fleet preventive maintenance in the Charlotte area.
Air brakes are the system inspectors look at first and the one drivers trust without thinking. A small leak or a dragging slack adjuster can turn into an out-of-service order at the scale house or a glazed drum on the long downhill stretches toward the mountains.
Components we repair
- Service and spring brake chambers (Type 16, 20, 24, 30 and long-stroke variants)
- Automatic slack adjusters
- Air dryers and desiccant cartridges
- Compressors and governors
- Relay, quick-release, treadle and parking-control valves
- Air lines, gladhands and tractor protection valves
- S-cam brake shoes, drums and air disc brake pads
Performance specs we check
Build-up and governor settings
Governor cut-out generally falls between about 120 and 135 psi, with cut-in no lower than 100 psi. Build-up from 85 to 100 psi should happen within the time the manufacturer specifies.
Leak-down
With the engine off and brakes released, a combination vehicle shouldn't lose more than 3 psi per minute; with the service brakes applied, no more than 4 psi per minute.
Pushrod stroke
Each chamber's applied stroke is measured at 90–100 psi against its readjustment limit. An automatic slack that keeps going out of adjustment is a symptom — usually of a worn cam bushing or foundation brake problem — not a reason to keep manually adjusting.
Repair sequence
- Pressure and leak tests with a soapy-water or ultrasonic check.
- Chamber, slack and foundation brake inspection wheel by wheel.
- Cage spring brakes safely before any chamber removal.
- Replace parts, re-measure stroke and road-test.
Parts quality and service life
Spring brake chambers should be replaced as complete units rather than disassembled. Use SAE J1402-rated hose and DOT-marked fittings, and change the air-dryer cartridge on schedule — oil and water carried past a spent dryer shorten the life of every valve downstream. Brake shoes and pads should carry an FMSI number and meet the axle's rating.