Product Description
IDLER CASTER
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
Wheel Dimensions
| Material | |
| Outside Diameter | 8 |
| Inside Diameter | 2.25 |
| Width Side to Side | 4 |
| Tread Profile | |
| Bore Depth | 0.63 |
| Hub Width | |
| Bore Outside Diameter | 2.4404 |
Frequently Asked Questions
Q: What is the function of the SU S684-EZ idler caster in a lift truck assembly?
A: The SU S684-EZ idler caster is typically a load-bearing or support wheel (non-driving) on the truck chassis. It does not transmit power but supports the truck weight and stabilizes steering. The idler must rotate freely without seizing. It experiences sideways and vertical loads. Any binding, wobbling, or noise indicates bearing problems, swivel damage, or wheel flat-spotting that requires immediate replacement.
Q: Can the SU S684-EZ idler wheel be interchanged with a load wheel like the SU S684-EZ-A?
A: Physically, yes, since they share the same 8x4 dimension and 2.25 inch bore. However, do not do this. Idler casters are designed for free rotation under load, while load wheels are engineered for powered drive and heavier lateral forces. Installing an idler wheel where a load wheel belongs creates poor steering response and accelerates bearing failure. Always install the wheel type specified for that position.
Q: What indicates that the SU S684-EZ idler caster needs replacement?
A: Replace the SU S684-EZ if: the wheel does not spin freely when rotated by hand (bearing seizing), excessive radial play exists (more than 1/8 inch runout), the wheel is flat-spotted or chunked, the caster swivel joint is cracked or loose, or the truck pulls to one side despite proper alignment. Any of these faults degrades stability and increases steering effort, putting operator safety at risk.
Q: How do I replace the SU S684-EZ idler caster on an electric lift truck?
A: Raise the truck on a lift or jack and secure with safety blocks. Unbolt the caster assembly from the chassis (typically 2-4 bolts). Slide the axle shaft out of the caster fork and press off the wheel using a bearing puller or wheel press. Press the new SU S684-EZ wheel onto the axle (press on the bore ID only, never on the rubber). Reinstall the caster assembly and torque bolts to 40-60 foot-pounds. Spin the wheel to confirm free rotation before lowering the truck.
Q: What bearing type does the SU S684-EZ idler caster use?
A: Most SU S684-EZ idler casters use sealed roller bearings or grease-packed ball bearings rated for 8-inch wheel diameters. The exact bearing type depends on the caster housing design. If the caster is grease-lubricated, repack bearings every 12-18 months or if you observe grease leakage. If sealed, no maintenance is needed until replacement. Do not mix bearing types; always replace with the OEM equivalent.