The Castair Replacement Motor Hub with 7/8" Shaft (LX78) fits Cast Air compressor assemblies where the electric motor uses a 7/8" diameter output shaft. This is a mid-range shaft size — larger than the 5/8" found on the smallest units, but smaller than the 1" and up sizes used on higher-horsepower models. Before ordering, measure your motor shaft with calipers. A 7/8" shaft measures 0.875" in decimal — if your measurement is different, select the corresponding LX hub for your actual shaft diameter.
What the Motor Hub Does
The motor hub is the mechanical interface between the electric motor shaft and the compressor pump's drive system. It carries the belt sheave (on belt-driven units) or serves as the coupling interface on direct-drive models. The hub takes the full rotational load of the motor — including the inrush torque spike that happens every time a loaded compressor starts. When this part wears or cracks, the result is vibration, premature bearing wear, belt alignment problems, and eventually a compressor that can't maintain pressure because it can't transfer power properly from motor to pump.
Key Features
- 7/8" Shaft Bore: Machined to 0.875" bore diameter for correct fit on compatible motor shafts
- Cast Air OEM Part: Factory spec dimensions for compatible Cast Air compressor models
- Precision Machined: Maintains concentricity between motor shaft and drive assembly
- Direct Replacement: Drops in without modification on compatible units
Technical Specifications
- Part Number: LX78
- Shaft Diameter: 7/8" (0.875")
- Component Type: Replacement Motor Hub
- Manufacturer: Cast Air
- Price: $19.25
Note: Manufacturer's product page was unavailable at time of writing. Confirm compatibility with your Cast Air model number before ordering.
When You Need This Part
- Hub is cracked, scored, or developing play on the motor shaft
- Compressor vibration is increasing — often first noticed as more noise at startup
- Belt won't stay in alignment despite correct tension and pulley alignment
- Motor replacement — new motor ships with a bare shaft and you need a hub to fit the drive assembly
- Preventive maintenance on a compressor approaching high-hour service intervals
LX Series Hub Lineup — Get the Right Size
- LX58 — 5/8" shaft
- LX78 — 7/8" shaft (this part)
- LX100 — 1" shaft
- LX118 — 1-1/8" shaft
- LX138 — 1-3/8" shaft
Why Buy From OEM Diagnostic Tools?
We stock the full Cast Air LX hub series and have been supplying shops with compressor parts since 2016. When a motor hub fails, you need the correct part the same day — not a week later. Free shipping on qualifying orders. If you need help confirming the right hub for your specific Cast Air compressor, call us with the model number.
Call 866-217-0063 for quick answers and help!
