ZZ vs 2RS Bearings: Seal Type Comparison for Speed, Dust and Moisture

ZZ and 2RS are the two most common seal designations on deep groove ball bearings, and they describe completely different protective architectures. ZZ is a stamped metal shield seated in a groove on the outer ring and running with a small clearance from the inner ring, so nothing touches anything during rotation. 2RS is a rubber lip bonded to a steel carrier that presses against the inner ring with a defined interference, so contact is continuous on both faces. Because a metal shield admits fine airborne dust along its clearance gap while a contact seal blocks dust, water spray and corrosive gas, 2RS suits exposed equipment and ZZ suits clean, high-speed or continuous-running installations.

That design difference propagates into every other property buyers compare. The contact seal adds friction, and friction becomes heat, so 2RS runs at a lower reference speed and produces more starting torque. Our 6006 2RS deep groove ball bearing is published with high speed rotation for that reason, while the 6002 ZZ low friction and low noise bearing is positioned for electric motor and textile spindle duty.

Everything in this comparison assumes both bearings share the same internal geometry. The seal suffix changes only what happens outside the rolling elements, so bore, outside diameter, width, dynamic load rating and clearance stay identical between a 6006 ZZ and a 6006 2RS of the same series. That is why seal selection is made after the series is fixed.

What the Suffixes Actually Specify

ZZ specifies a non-contact metal shield on both faces and 2RS a contact rubber seal on both faces, and the single-letter codes follow the same logic. The Z designation comes from the German Zahl notation for shield. Both arrangements fall inside the closure options published for these families: Open, Z, ZZ, RS, 2RS and 2RZ. The suffix also sits outside the dimensional standards, so a bearing dimensioned to the boundary and geometrical product requirements of ISO 492 accepts either closure in the same housing.

• Open means no seal or shield at all, so grease is retained only by the internal geometry and the bearing must run in oil or be relubricated.
• Z means one metal shield on one side only, protecting a single face and leaving the opposite face exposed.
• ZZ means a metal shield on both faces, both running non-contact with a small clearance to the inner ring.
• RS means one contact rubber seal on one side only, giving protection on a single face and open exposure on the other.
• 2RS means a contact rubber seal on both faces, both lips pressing against the inner ring for the life of the bearing.
• 2RZ means shields combining a metal plate with a low-friction sealing element, used where a higher speed limit is needed alongside partial protection.

The single-letter versus double-letter distinction matters more than it looks. On a shaft where contamination enters from one direction a one-sided seal can be sufficient; on a shaft exposed from several it quietly fails.

Axis One: Protection Against Dust, Moisture and Corrosive Gas

2RS is substantially better than ZZ at keeping contamination out of the rolling element path, and this is the axis on which the choice is usually made. A metal shield forms a labyrinth path with a clearance measured in fractions of a millimetre, so it retains coarse debris while fine airborne dust migrates along the gap into the cavity. A contact rubber seal has no such path.

It is worth being precise about that dust-tight condition. According to the International Electrotechnical Commission, an ingress protection rating grades how well an enclosure resists solids, its first numeral running from 0 for no protection to 6 for no ingress of dust, with test conditions in IEC 60529. Bearing seals are not enclosures and carry no IP rating, so a stated equivalence is shorthand, not a tested classification.

The failure mechanism explains why ZZ fails in dust rather than merely wearing faster. Fine dust that enters a ZZ bearing mixes with the grease and stays in the rolling contact zone, where it is rolled repeatedly under load, producing abrasive wear and noise that usually precedes a visible defect.

Moisture follows the same logic and adds a second effect. Water entering a ZZ bearing can wash the grease film at the rolling contacts, so the load-carrying film thins and rolling contact fatigue accelerates. A contact seal slows that process without eliminating it: 2RS resists water ingress, but a sealed ball bearing is not hermetic.

What our own seal development adds

Our seal development work is concentrated precisely on this problem. We developed a special rubber seal using Japanese technology that is tougher at high temperature than ordinary NBR rubber seals, and the tight contact seal design exists to keep chlorine gas, corrosive gas and particulate impurities out of the bearing interior during glove production. Paired with high temperature grease rated above 250 °C, we state that the resulting bearing gives at least 12 months of service. That claim is tied to a specified seal and grease, not to 2RS as such.

One further point is frequently missed: neither suffix addresses chemical attack on the lubricant from washdown cleaners. Alkaline and solvent-based products attack grease regardless of seal type.

Axis Two: Speed, Drag Torque and Heat

ZZ allows the higher shaft speed and the lower drag torque of the two, and the reason is the contact itself. A non-contact shield produces no rubbing friction, so the only frictional losses in a ZZ bearing are those of the rolling elements and the lubricant film. A contact seal adds continuous rubbing loss on both faces, and that loss rises with speed as friction outgrows the supporting hydrodynamic film.

Published speed ratings are therefore not transferable between suffixes. Confirm that both speed figures were derived with the same seal configuration, because a catalogue figure quoted for a ZZ or open configuration says nothing about what the 2RS version tolerates. As a planning rule for the 60 and 62 dimension series, engineers commonly run a 2RS installation at roughly 70 to 80 percent of the ZZ figure and confirm it against the specific datasheet.

Drag torque matters most where the available driving torque is small. In a low speed actuator, a damper mechanism, a tensioner or any start-stop duty, the contact seal consumes a share of the available torque before the load is applied.

Low noise and the electric motor case

Noise follows from the same physics, and this is why the two suffixes position themselves differently. Our 6002 ZZ series is published as a low friction and low noise product for electric motor and textile machinery use, where the requirement is high running accuracy and optimised contact geometry. A contact seal against the inner ring at speed is an extra noise source a shielded bearing does not have.

Our published quality control regime matters here, because noise is treated as a measured characteristic. Every good passes through our internal quality management system with noise testing, grease application checks, sealing checks, hardness checks and dimensional measurement.

Axis Three: Grease Life and Relubrication

ZZ generally supports longer grease life than 2RS in the same application, and the mechanism is heat rather than lubrication chemistry. Grease life in a sealed bearing is governed mostly by thermal degradation, and a contact seal adds heat continuously. Because the 2RS seal adds frictional heat, grease in a 2RS bearing degrades faster, so ZZ typically gives the longer service interval in the same duty cycle. Rating life calculated under ISO 281 should therefore be read as a load and speed result rather than a seal result: that standard covers fatigue under conventional conditions and does not model contamination or abrasive wear.

Neither suffix makes a bearing re-greaseable. Opening a 2RS bearing to re-grease it destroys the contact seal, leaving a unit that is functionally ZZ or open with a compromised seal geometry. If an application genuinely requires relubrication, that requirement decides the seal type before contamination or speed does.

Axis Four: Temperature Envelope

The temperature envelope of a sealed bearing is set by the weaker of two limits, and the seal type frequently decides which binds. The ZZ metal shield carries almost no temperature penalty of its own because it introduces no elastomer into the load path. The 2RS rubber seal introduces an elastomer whose continuous ceiling is a property of the compound.

For engineering purposes NBR is commonly specified up to roughly 100 to 120 °C continuous and FKM up to roughly 200 °C, and both figures are compound and supplier dependent. Above those ranges a contact seal using our Japanese-technology high temperature rubber is specified instead. Compound and lubricant must be chosen as a pair, because a seal correct for a 120 °C duty hardens and loses its interference fit on a hot application.

Where 2RS loses despite better protection

Two cases regularly surprise buyers who assume the better-protected option is always safer. The first is sustained high temperature with modest contamination, where the steel shield outlives the rubber lip. The second is a very cold start, where a stiffened lip raises starting torque enough to stall a drive. In both cases the answer is ZZ.

Axis Five: Cost, Availability and Fit-Up

2RS costs more than ZZ at the same bore size, and the reason is material rather than complexity. The additional cost is the elastomer compound, the steel carrier, the bonding process and the extra sealing checks, none of which apply to a stamped shield pressed into the outer ring. That difference is rarely deciding, because the failure cost of an unprotected bearing in abrasive dust normally exceeds the price gap by a wide margin. Availability favours ZZ as the more common configuration, and fit-up favours it because a pressed shield cannot be damaged by handling, whereas a nicked contact lip does not look damaged from outside.

It is worth stating the honest case for ZZ in applications buyers often default to 2RS. If the equipment is enclosed, contamination is coarse and infrequent, and the bearing runs continuously at high speed or in a low torque duty, then the extra protection of 2RS buys very little while costing speed, drag and grease life every hour.

The Five Axes Side by Side

The comparison only works as a set, because each axis constrains the others.

How to Specify the Right One: Six Steps

The order of these steps matters. Working from the suffix outward rather than from the environment inward produces bearings that are nominally correct and operationally wrong.

Step 1: Fix the bearing series before the seal

Select bore, outside diameter, width, dynamic load rating and clearance class first, because the seal suffix changes none of them. Our series list covers the 6000, 6200, 6300, 6400, 6800, 6900, 16000 and 62200 families.

Step 2: Map the contamination profile honestly

Write down what actually enters the bearing rather than what the equipment is called. Airborne abrasive dust, washdown liquid, corrosive gas, food wash and clean indoor air are different environments, and only the first three justify a contact seal.

Step 3: Confirm the speed requirement against the sealed rating

Compare the required shaft speed against the reference speed published for the seal configuration you intend to buy. If the application runs within roughly 80 percent of the published 2RS figure, the seal is not limiting.

Step 4: Set the torque budget before choosing a contact seal

For start-stop, damper and tensioner duty, calculate the torque needed to break the bearing free from rest and compare it with what the drive can deliver. This step is most often skipped, and it produces a motor overload on the first cold start.

Step 5: Match the seal compound and grease to the temperature ceiling

Decide the compound and the lubricant as a pair. NBR, FKM and our high temperature rubber cover different ceilings, and the same decision governs whether the seal keeps its interference fit or hardens and leaks.

Step 6: Confirm vibration class and clearance, then validate on a sample run

Our published options are tolerance ABEC-1, ABEC-3 and ABEC-5, vibration V3, V2 and V1, and internal clearance C2, C3, C4 and C5. Choose them from the noise requirement and the fit, then confirm the assembled result on a sample run.

Which Seal Should You Choose?

Choose ZZ when the equipment is enclosed or contamination is coarse and infrequent; when the duty is continuous running at high speed in an electric motor, fan or textile spindle; when starting torque is small; or when the operating temperature sits near the continuous ceiling of the available rubber compounds.

Choose 2RS when the bearing is exposed to airborne dust, abrasive particulate, washdown liquid or corrosive gas; when the equipment operates outdoors, in agriculture, in construction machinery or in dusty industrial process; or when premature failure with unplanned downtime costs more than the price difference.

Our bearing factory catalog for OEM buyers carries the full closure range across the major dimension series, and the 6206 ZZ superior deep groove ball bearing is a typical shielded configuration where noise and friction dominate.

Frequently Asked Questions