Spherical plain bearing: wear checks and fitting

A spherical plain bearing lets a pin joint swivel and tilt while it carries heavy load. You find it in the eyes of hydraulic cylinders and in the pivots of loaders, excavators and tipper bodies. The steel-on-steel type, such as the IKO GE100GS2RS, must be greased on a schedule. When grease stops reaching it, the joint wears loose or seizes, and the cylinder pays for it.

This guide is for fleet and workshop managers in Indonesia. It explains what the bearing does, how to read its part number, which wear signs to look for, and how to fit a new one without damaging it.

What a spherical plain bearing does

The bearing has two rings. The inner ring has a ball-shaped outer surface. The outer ring has a matching hollow inside. The two rings slide on each other, so the shaft can tilt as well as turn. IKO describes these bushings as self-aligning parts that take a large radial load and an axial load in both directions at the same time (IKO spherical bushings catalogue).

IKO says the steel-on-steel type suits alternate loads and shock loads, and is used mainly in industrial and construction machinery. SKF also rates its steel/steel bearings for heavy static, alternating or impact loads.

On a cylinder, the bearing in the rod eye or base eye takes up small misalignment between the cylinder and the machine. Fluid Power Journal notes that a swivel rod eye can be used to reduce side loading where some misalignment cannot be avoided (misaligned cylinders article).

How to read GE100GS2RS

The part number tells you most of what you need:

• GE is the metric radial spherical plain bearing series.
• 100 is the bore in millimetres.
• GS is IKO's heavier series. IKO says GE...G and GE...GS types have larger load capacity and larger tilt angles than GE...E and GE...ES types.
• 2RS means a double-lip seal on both sides. IKO says these polyurethane seals keep grease in and dust out.

Published data for the IKO GE 100 GS-2RS gives a 100 mm bore, 160 mm outside diameter and 85 mm width (GE100GS-2RS technical sheet). The technical sheet lists SKF GEH100ES-2RS as an equivalent designation. Do not confuse it with GE100ES-2RS, which shares the 100 mm bore but is a smaller bearing of 150 mm outside diameter and 70 mm width. Measure the old bearing or check the parts book before you order.

FDA lists the IKO GE100GS2RS spherical plain bearing as a sealed, steel-on-steel bearing that requires maintenance, in metric sizes.

Why grease matters on steel-on-steel bearings

The words "requiring maintenance" mean the bearing must be greased. SKF says steel/steel bearings must be greased before use and relubricated regularly to reduce friction and wear and to protect against corrosion and dirt. IKO's GE...GS type has an oil groove and oil holes in both rings so grease can reach the sliding surfaces.

IKO recommends periodic grease lubrication and a shorter interval during the first period of operation. It notes that lithium soap grease of NLGI grade 2 with molybdenum disulfide is widely used. Follow the grease and interval in your machine manual first.

If the pivot is on an auto-lube system, check that its injector actually delivers. Our guide to grease injector checks covers this.

Wear signs to check at the cylinder eye

IKO defines the end of bearing life as the point when the bushing no longer works normally because of wear, larger internal clearance, higher sliding torque or higher temperature. In the workshop, look for:

• Free play or knocking at the pin when the cylinder changes direction.
• A dry joint, or grease that will not pass through the fitting.
• Torn seals and dirt packed around the bearing.
• An eye worn oval across the pin. Fluid Power Journal links this to a lack of lubrication or long use.
• Scuff marks on one side of the rod or uneven wear side to side in the eye. The same article points to misalignment.

A seized eye is more serious. The article explains that a dry rod eye can seize on its pin, and the turning pin can then bend or break the rod near the eye. Side loading also wears the rod bearing out of round, so the rod seal starts to leak. If you already see a leak, read hydraulic cylinder leaking: rebuild or replace.

Fitting a new bearing

SKF and IKO give the same basic rules:

1. Check the fits. SKF says both rings must be held firmly so they do not creep on their seats, which usually needs an interference fit (SKF radial location). Measure the pin and the eye bore for wear before fitting.
2. Press, do not hammer. SKF says never to drive the bearing in with a hammer or pin punch, and never to push the mounting force through the sliding surfaces (SKF mounting guidance). Use a dolly or tube on the ring with the tight fit.
3. Do not wash it in solvent. SKF says washing the sliding surfaces with solvents, cleaners or oils can shorten bearing life.
4. Set the split at right angles to the load. The outer ring is split at one point. IKO says the split plane should sit at right angles to the load direction.
5. Grease it before the machine goes back to work.

For large bearings, SKF recommends heating the bearing or the housing rather than pressing cold. Keep within the temperature limit of the seals.

Related parts and pages

FDA quotes bearings for trucks, trailers and heavy equipment, including a Volvo spherical plain bearing, 20806212. Browse the bearings category or Volvo parts on FDA, or search any number on the parts search page.

When the bearing change is part of a cylinder rebuild, see hydraulic seal kits. For new cylinders, including custom eyes and mountings, see the hydraulic cylinders page.

What to send for a quotation

To get the right bearing quoted quickly, send:

• The part number on the old bearing, such as GE100GS2RS or GEH100ES-2RS.
• The bore, outside diameter and width if the marking is gone.
• Whether it is open or sealed (2RS).
• The machine or cylinder it comes from, and the quantity.
• A photo of the bearing and the eye, and your delivery location in Indonesia.

Send these through the quotation request form.