Advantage Trimetal bearing

Trimetal bushing bearing What do you need to know? Advantage of the trimetal?

Here and there we hear many bells on the bearing:

"The bearing without pins it turns in the hooks.." 
"I fit the Trimetallic bearing, the bimetallic it's worthless"
"I can put back my old conrod bearing, it's no problem"
A conrod bearing actually what is it?

A bearing is a workpiece designed to reduce friction, to avoid wear or seizure of a bearing or a rotating assembly. There are various types of bearing such as rings for example.

Let's have a closer interest in the conrod bearing. In the automobile we use various types of bearings, bimetals, Trimetallics, Sputer...
Here is how the different types of bearing bearing are made on the market

In the automotive industry, two-metal bearing are used, therefore steel and tin-foil coating (Figure 2). One speaks of two-layered bearing, these two layers are made by colamination (illustration 1)

img_000410  1-Illustration of co-laminating, it creates a welding

The Trimetallic bearing has a different design, it consists of 3 layers (see illustration 3), including the electrolytic coating that gives a milky white appearance to the bearing, (illustration 4), this coating is between 10 and 30 µm. The Cushion Can be manufactured by casting or sintering.


1       2-Illustration of a bimetallic bearing

(Source: Federal Mogul – Glyco)

2      3-Illustration of a trimetallic bearing

(Source: Federal Mogul – Glyco)

Trimetal bearing  4 – Illustration of the color of a trimetal bearing with electrolytic coating

Here is the cut-view composition of the different types of bearing

bimetallic bearing Material-Trimetallic bearing

(Source: Lubrication Damage – Jean Louis Ligier Edition Technip)

The 3 criteria that determine a bearing are:

-Load Resistance
-Temperature Resistance
-The resistance to gripping

A bearing is always a compromise, indeed it is impossible to have the perfect mix between these 3 criteria. 

Compare these 3 criteria between SAE 783 bimetallic bearing and SAE 794 Trimetal

Features Bimetal bearing

Characteristics of the SAE 783 bimetal bearing (Source: King Bearing)

The following are the appellations of some manufacturers to refer to SAE 783: ISO AlSn20Cu, Glacier AS 15, Clevite CL 157, Federal Mogul TR-20, ACL F820, Daido A20


Trimetal Features


Characteristics of SAE 794 trimetal bearing (Source: King Bearing)

The following are the appellations of some manufacturers to refer to SAE 794: ISO CuPb24Sn4, Glacier SP, Clevite F250, Federal Mogul HF16, ACL F250, Daido L23, Glyco 41




It is clear from this illustration that a choice of type of bearing should be made according to the use. However, it is seen that Trimetal has a higher loading capacity than bimetal, while having a better resistance to binding, only the wear resistance is slightly lower. The resistance to wear is nevertheless a lesser criterion on a prepared sports engine which is usually dismantled before the bar of 100,000 km.

The last example the Sputter, the Sputter is a trimetallic bearing with a coating deposited by cathodic spray, this type of bearing is reserved for very high loads and is not actually available on the market of the "current" car.

               Here is how a sputter is answered to the 3 criteria stated before:

sputter bearing


            A bearing without ergot it turns... myth or Reality??

   We often read on the forums, the Facebook pages etc... ' These damn bearing without pins turned etc... »

            How does a bearing actually hold in the conrod?

       Physio bearing

(Source: Lubrication Damage – Jean Louis Ligier Edition Technip)

             It is shown on this diagram that the opening of the bearing makes that at the fitting it closes slightly and thus hold in the hat or in the conrod without it falling when you handle the conrod during assembly.

              The role of the conrod is paramount. Contrary to the ideas received, the ergot is not in charge of holding the bearing in the head of the conrod, this allows a good radial placement of the bearing but it is far from indispensable.

                    How does the bearing fit in the housing then?

                    You may not know it but a stick bearing is always slightly larger than the housing in which it should be placed. These few hundredths in addition generates an overshoot of the tiny bearing, both a passing of the cap, and an overshoot at the level of the conrod.

                      When you assemble these 2 parts, each of the bearing will come slightly to force, this is what will hold the bearing in front of the enormous efforts of an engine.


It is therefore IMPERATIVE, to make a metrology of your living quarters:

Too small a housing will cause a twisting of the bearing, this could cause metal-to metal contact, a fatigue of the bearing, a bad oil film etc.


A housing Too large will cause bearings that rotate, axial motion of the bearings and a poor heat transfer, thus a probable warming of the cushion and tightening

It is therefore imperative to be sure of the metrology of its coelles before any reassembly... a bearing that turns it is not by chance...

Small tip To check the proper holding of the bearing:

  • Mount your bearing set in the
  • Tighten your screw to the torque
  • Completely loosen one of the two screws
  • Normally the loose side should open under the pressure of the bearing which is released
  • Measure this gap with a shim of thickness the value must be 3/100 (see illustration)
  • Test opening conrod
Can I reassemble my old bearing?

Sometimes you hear some people who wish to reassemble their old bushings as they have nothing...

Certainly, to the eye a bearing may look new, however difficult to detect if the bearing has not integrated small metal particles, one does not have a superficial defect of a few microns...

It is important to know that the conrod bearing have the ability to absorb the micro metal particles that are strolling in the oil and which have not been filtered by the oil filter, in fact by rotating the interconnectors create an area of depression, which attracts the oil and These waste microphones. These are particles have sizes of a few microns, this is how each type of bearing has a intégrativité factor (absorption of waste).

Even if a bearing set that has already turned is not necessarily good for the trash, it is best not to take any chances. Also a bearing that has turned a can be slightly distorted by a particle in the housing of the conrod or you will be impossible to reassemble it in the same place. Remember that an oil film is a few microns... at the sight of possible damage to the crankshaft better not to run this risk.


Custom bearing Manufacturing

Mespiecesauto can manufacture both metal (SAE 783) or Trimetal bearing (SAE 794). We can achieve standard ribs or grinding + 0.10, + 0.20, + 0.25 etc...

Attention However the bushing industry is a heavy industry, it is not possible to make 1 set to measure, it will of course have a small see medium series. The ideal is to switch to custom bearings when these are no longer available on the secondary market, or that the majority of crankshafts require corrective bearing.

You can consult us for any requests to