Cast Air P2B395H — 3.95" OD Dual-Groove B-Section Motor Pulley, Hub Mount
The Cast Air P2B395H is a 3.95" outside diameter motor pulley with two B-section belt grooves and a hub-mount bore configuration. It sits in the middle of the Cast Air small-to-mid dual-B-groove motor pulley range — larger than the 3.55" P2B355H and slightly smaller than the 4.45" P2B445H. The hub-mount design means the pulley body does not have a machined bore; instead, a separately ordered hub (LX, SD, or SK series, depending on shaft size) locks into the pulley center and clamps to the motor shaft. This gives the P2B395H flexibility across multiple shaft diameters without stocking a separate fixed-bore pulley for each combination.
The 3.95" OD is close to the 4" diameter common in fixed-bore pulleys, but is a distinct part with distinct drive ratio characteristics. If your compressor originally came with a 3.95" motor pulley, replace it with the P2B395H. Do not substitute a 4.0" pulley — the pump speed will be slightly higher than designed, which shifts the motor load curve and can cause nuisance tripping on compressors that are already running near motor capacity at operating pressure.
Pulley Specifications
- Part Number: P2B395H
- Outside Diameter: 3.95"
- Bore Configuration: Hub mount (bore depends on hub selected)
- Number of Grooves: 2
- Groove Profile: B-section
- Belt compatibility: Two B-section V-belts (matched pair recommended)
- Material: Cast iron
- Price: $38.50 (hub sold separately)
Selecting the Correct Hub
The P2B395H is a hub-mount pulley. You must order a separate hub matched to your motor shaft size. Cast Air hub options:
- LX58: 5/8" shaft
- LX78: 7/8" shaft
- LX100: 1" shaft
- LX118: 1-1/8" shaft
- LX138: 1-3/8" shaft
- SD138: 1-3/8" shaft (SD taper-lock)
- SD158: 1-5/8" shaft (SD taper-lock)
- SK158: 1-5/8" shaft (SK taper-lock)
- SK178: 1-7/8" shaft (SK taper-lock)
Measure your shaft diameter with calipers before ordering. Do not estimate. Common motor shaft sizes for Cast Air compressors in the size range this pulley serves include 7/8" (LX78) and 1" (LX100). If you are replacing an existing hub-mount pulley, the old hub's markings will show the shaft size and hub series.
Drive Ratio at 3.95" OD
The motor pulley OD directly determines how fast the pump runs. To put the 3.95" diameter in context:
- At 1750 RPM motor speed with a 10" pump pulley: pump runs at approximately 691 RPM
- Compared to 3.55" (P2B355H): the 3.95" motor pulley increases pump speed by approximately 11%
- Compared to 4.95" (P2B495H): the 3.95" motor pulley runs the pump approximately 20% slower
- Replace like-for-like: Match the 3.95" OD to maintain the original pump speed specification. Changing pulley diameter changes CFM output and motor load.
When Hub-Mount Pulleys Are the Right Choice
- Your shaft size is not available in a fixed-bore pulley: Fixed-bore pulleys in the Cast Air lineup are available at 5/8", 7/8", 1-1/8", and 1-3/8" for specific diameters. Hub mounts cover all shaft sizes.
- The original equipment used a hub mount: If you pull the old motor pulley and it has a hub locking ring or taper bushing, replace it with the same hub-mount configuration.
- You want to separate the pulley and hub replacement cycles: Hubs typically wear slower than pulleys (groove wear). A hub-mount system lets you replace only the worn component.
Dual-Belt Drive Maintenance Notes
- Always replace belts in matched pairs: Installing one new belt alongside an old belt means the stiffer old belt carries more load, wearing faster and putting uneven side loads on the shaft bearings.
- Check groove alignment: The motor pulley grooves and pump pulley grooves must be in the same plane. Misaligned grooves cause the belts to run at an angle, generating heat and wearing both the belt and groove edges prematurely.
- Inspect the pump pulley at the same time: When replacing the motor pulley, check the pump pulley grooves for wear and verify the pump shaft bearings are free of play.
Full 2B Hub Motor Pulley Comparison
- P2B355H: 3.55" OD, hub mount — $38.50
- P2B395H (this pulley): 3.95" OD, hub mount — $38.50
- P2B445H: 4.45" OD, hub mount
- P2B495H: 4.95" OD, hub mount — $66.41
- P2B335-7/8: 3.35" OD, 7/8" fixed bore — $38.50
Technical Specifications
- Part Number: P2B395H
- Outside Diameter: 3.95"
- Bore: Hub mount (hub ordered separately)
- Number of Grooves: 2
- Groove Profile: B-section
- Material: Cast iron
- Price: $38.50 (hub not included)
Why Buy From Air Compressor Factory Direct?
Hub-mount pulleys require you to get two parts right. We stock both the P2B395H and the full LX, SD, and SK hub range. Call us with your shaft diameter and we will build the complete parts list for you — pulley, hub, and belts if needed — so you can do the job with one order and one shipment.
- Free shipping on qualifying orders
- Free tech support: Call 866-217-0063 — confirm your shaft size and we will identify the right hub
- Full manufacturer warranty on all Cast Air parts
- Honest guidance: We will verify you have both the pulley and the matching hub before you complete the order
Call 866-217-0063 for quick answers and help!
