What is the difference between ES and 2RS?
ES is the open version: a split outer ring with lubrication groove and holes. 2RS is the same bearing with rubber seals on both sides (Q1-01). Makers typically offer three options: open, 2RS sealed to protect against dust and contamination, and a reinforced seal for harsh environments. A typical ES-2RS has reinforced molded rubber lip seals that withstand high grease pressure during greasing and keep outside contamination out.
What does a seal do, and what does it not do?
It keeps contamination out and lubricant in. Sealed spherical bearings are meant to minimise the ingress of contaminants onto the bearing surface and to help hold the lubricant inside. One maker gives its seal an operating range of −10 °F to +250 °F (about −23 °C to +121 °C) and says special seal materials are available beyond it. Other makers give other ranges, so read the range for your seal in the maker's description (Q1-12).
A seal is not a guarantee against water. Water or chemical ingress, unsuitable cleaners and poor boots or wipers are the usual causes of corrosion in the ball and ring, and jets should not be aimed straight at the spherical interface. A lip seal is made to keep dust and splash out, not to resist a high-pressure jet at close range.
What do you have to allow for with a sealed bearing?
- Room for the seal. There must always be enough space for the seal, particularly with 2RS models, so it does not touch the surrounding parts. The tilt angle in the tables must not be exceeded (Q1-05).
- Careful greasing. With a central lubrication system, too high a pressure or dose could loosen the seals on sealed versions. Grease until it comes out at the seal, and no further (Q1-08).
- Inspection. The first check for corrosion symptoms is the condition of the seals and boots (Q1-09).
Which materials suit wet or corrosive service?
The seal only slows the water down. What the ring and the ball are made of decides how long they last when water does get in.
- Plain bearing steel, with a protective finish. The finish (plating, phosphate, black oxide or paint) protects against light moisture. Once it is scratched or worn through at the sliding surface, bare steel is exposed, so it suits dry or occasionally damp service, not constant wetting.
- Stainless steel. Better for wet, washdown and mildly corrosive service. The grade matters, and stainless is not immune: chlorides (sea water, de-icing salt, some cleaners) and crevices can still cause pitting and crevice corrosion. Stainless against stainless tends to gall, so stainless bearings are usually built with a self-lubricating liner or a treated sliding surface. Ask the maker which sliding pair goes with the stainless rings.
- Self-lubricating liner. A PTFE liner does not rust and does not wash out like grease, which helps in washdown. Grit and unsuitable fluids still damage it, and the steel around it can still corrode (Q1-02).
- Grease. Water and cleaners can wash grease out. In food and wet areas, use a grease that is validated against the cleaners and temperatures in use, and dry the joint after washdown.
- Seal and boot material. Check it against the fluid, not just the temperature. Rod end material choices are covered in K01-Q1-07.
What suits each place?
| Condition | What to look at |
|---|---|
| Dust and dirt | A sealed type (2RS), or a reinforced seal for harsh conditions |
| Splash and rain | Sealed; plated or stainless rings; check the grease path stays clear of water |
| Washdown | Sealed, plus boots or wipers; keep jets off the ball; stainless rings; a grease validated against the cleaners; dry the joint after |
| Corrosive chemicals or marine | Stainless rings, sealed, with a seal and boot material rated for the fluid; check chloride and crevice attack |
| Very fine abrasive dust (cement, grit) | Sealed plus a boot; consider a liner type only if the dust is kept out, since grit wears a liner as well |
Do maintenance-free bearings need seals?
They are often supplied with them. Some maintenance-free types have integrated seals in some sizes, and heavy-duty multi-lip seals exist for dirty service. A PTFE liner is damaged by grit as well, so keep dirt away from it (Q1-02).
What do mud, sand and water change on an off-road vehicle?
They make the seal question the main one, not a detail. A 2RS seal keeps out dust and splash, not a pressure jet or a joint that sits submerged. On a vehicle three points need attention:
- Tilt at the end of travel. At full angle the seal on one side can be squeezed while the other opens, so check the seal clearance with the arm at full bump, droop and twist (Q1-05).
- Packed mud. Dried mud around a seal turns into an abrasive paste when the joint moves. Rinse it off at low pressure before the next trip, and keep the jet off the seal. A boot or cover that does not trap mud against the seal helps; one that does, hurts.
- Salt and water. Road salt and sea water put chlorides on the joint, so the ring material and finish matter as much as the seal (see the materials list above).
A liner type without seals is a poor fit for sand: grit embeds in the liner and wears the ball. If the joint cannot be kept clean, plan the replacement interval around that, and take the figure from the vehicle's designer. SYZ's spherical plain bearing buyer's guide and off-road rod ends page cover the bearing and the off-road use.