Product Description
Idler caster assembly, SKU SU 684, engineered for electric lift trucks and pallet jack equipment. Constructed with a high-grade polyurethane wheel (95A Shore hardness) and designed for direct replacement of defective or worn caster units. Provides dependable, non-marking operation for electric truck applications, utilizing standard mounting dimensions and sealed bearings for optimal service life.
Specifications: 8.000 inch diameter x 4.000 inch width (8.000" x 4.000" | 8 x 4 wheel | 8 x 4 | 203.20mm x 101.60mm)
Specifications
Material
| Polyurethane Specification | Polyester-based polyurethane, 95A Shore |
| Core Material | High-impact polymer or steel core |
| Finish | Machined and precision-molded |
Part Numbers
| Manufacturer Part Number | SU 684 |
| Superseded / Alternate Part Number | SU S684 |
| Equivalent Part Number | SU 684-XL-A |
| OEM Part Number | SU 684 |
| Cross-Reference Part Numbers | SU S684, SU 684-XL-A |
Wheel Dimensions
| Outside Diameter | 8 |
| Inside Diameter | 2.25 |
| Width Side to Side | 4 |
| Bore Depth | 0.63 |
| Bore Outside Diameter | 2.4404 |
Frequently Asked Questions
Q: What is the part number history for SU 684?
A: SU 684 is the current manufacturer part number. Superseded alternate part number is SU S684 (older designation, no longer in use). Equivalent part number is SU 684-XL-A. If you see SU S684 on old documentation, it refers to the same idler caster assembly. Always order using the current SU 684 designation to ensure you receive the correct revision and updated bearing seals.
Q: What are the dimensions and material specification for SU 684?
A: SU 684 is an 8.000 inch diameter by 4.000 inch width idler caster assembly. Wheel material is polyester-based polyurethane at 95A Shore hardness, which provides wear resistance and low floor marking. Core material is high-impact polymer or steel (verify with product specification sheet for your serial range). Metric equivalents: 203.2mm diameter, 101.6mm width. This size is standard for electric lift trucks and pallet jack rear idler locations.
Q: What is 95A Shore hardness and why does it matter?
A: 95A Shore is a measure of polyurethane tread firmness. Higher Shore values mean harder, more durable material that resists gouging and cuts. 95A is mid-range: firm enough to provide good tread life on rough concrete, yet soft enough to provide traction and reduce floor shock. If you see lower Shore ratings (80-90A), the wheel is softer and marks floors more; higher ratings (100A+) are extremely hard but can be slippery on smooth floors. 95A is optimal for warehouse idler duty.
Q: What is the difference between SU 684 and SU 684-XL-A?
A: SU 684 and SU 684-XL-A are equivalent part numbers (cross-reference). Both refer to the same 8.000 x 4.000 inch idler caster assembly with 95A Shore polyurethane. The XL-A designation may indicate a newer revision or specific bonding technology. When ordering, use SU 684 unless your truck documentation specifies SU 684-XL-A. Both ship with identical dimensions and bearing specs.
Q: When should the SU 684 idler caster be replaced?
A: Replace the SU 684 if tread is worn flat, chunked, or separating from the hub. If the caster does not roll freely or produces grinding noise, bearing failure is likely and replacement is required. Sidewall cracks or permanent flat spots also require replacement. Under normal warehouse use (5-day work week, 8 hours per day), expect 2 to 4 years of service. High-traffic or outdoor use shortens lifespan to 1 to 2 years.
Q: How do I install SU 684 on an electric lift truck?
A: The SU 684 idler caster mounts to the rear frame of electric trucks and pallet jacks. Remove the old caster by unbolting or unpinning from the frame. Ensure the mounting surface is clean and bolt holes are not stripped. Align the new SU 684 caster with the frame mounting points and install bolts or pins. Do not over-tighten; this damages the bearing. Spin the caster by hand; it should roll freely with no wobble or noise. Verify ground clearance before operating the truck.