The choice between 2RS and 2Z is a trade between protection and speed, and it is decided by the environment first and the duty cycle second. Both are the same bearing underneath — same bore, same OD, same load rating — so the decision costs nothing to change and everything to get wrong.
| Criterion | 2RS | 2Z |
|---|---|---|
| Construction | Rubber lip in contact with the inner ring | Pressed steel disc with a gap |
| Friction | Highest of the standard options | Very low |
| Speed rating | 60–70% of open | 85–95% of open |
| Dust | Tight against fine dust | Coarse dust only |
| Water and splash | Resistant | Not resistant |
| Running temperature | +5 to +15 °C against 2Z | Reference |
| Relubrication | Impossible | Sometimes possible |
| Cost | Reference | 4–8% cheaper |
| Typical life in a dirty plant | Several times longer | Reference |
A 2RS bearing on a shaft running above roughly 70% of the open speed rating will overheat the lip. The rubber hardens, the lip loses contact pressure, grease escapes and the bearing fails — typically at a fraction of its calculated life, and usually without any contamination present. The failure looks like a lubrication problem and is actually a specification problem.
That is why the substitution is not symmetric: replacing 2Z with 2RS is safe on dimensions but risky on speed, while replacing 2RS with 2Z is safe on speed but gives up the protection that was the reason for the seal in the first place.
Is there water, washdown, fine dust or condensation? If yes, 2RS unless speed forbids it.
Compute ndm (bore mm × rpm). Compare with the sealed rating, not the catalogue headline figure.
Above 120 °C the NBR seal is out regardless. Move to FKM or to a shielded bearing with high-temperature grease.
If the position must be relubricated, neither sealed nor shielded works — use open in a sealed housing.
2RZ is the compromise most buyers do not know exists: a rubber lip that does not touch the inner ring. It seals better than a shield, adds a quarter of the drag of a contact seal, and keeps 80–90% of the open speed rating. For inverter-driven motors and high-speed pumps in dusty air it is usually the correct answer, and it costs only a few percent more than 2Z.
Dimensionally yes. Check the speed rating first: 2RS is typically 60–70% of the open rating, and exceeding it destroys the seal lip rather than the raceway.
2RS, by a wide margin. Fine abrasive dust passes a shield gap and acts as lapping compound. In that environment a shielded bearing often fails in months where a sealed one lasts years.
For splash and low-pressure washdown, yes. For high-pressure jets or immersion, no — a contact lip does not hold against pressure. Use a housed unit with a separate seal.
Not reliably. Rain and condensation pass the gap and emulsify the grease. Outdoors, use 2RS or a sealed housing.
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