High Spec Maruha Power Metal Bearing

The metal bearing that is a plain bearing to rotate crankshafts and connecting rods has a huge effect on the engine's performance and its lifetime.
You need to select metal bearings with higher quality, better capacity and more durability than others.

Maruha Power Metal Bearing includes 3 sizes to meet your needs from fine tunings to race ones. Its price range is the same as the genuine MIATA bearing's price, although our product has higher quality and better performance than the other ones.

You will be completely satisfied with Maruha's bearings.

[Features of Maruha Power Metal Bearing]

1. Oil groove, the troubleshooter

Our upper and lower main bearings have oil grooves to provide oil feeding into the oil holes on your crankshaft journal.
The improvement can increase the oil circulation to the conrod bearing that works under more severe conditions than the main bearing.
The grooves also allow Maruha's bearings to be used with tuning engines that drive in the hardest environments.

The red arrows show the oil flow.

Engine troubles are mainly caused by damage in connecting rod bearings, such as the hard vibrations, the bearing seizing by the poor oil circulation and so on. Increasing the oil pressure and quantity to improve the oil feeding is a general way to prevent the damage.

The genuine bearing has only one oil groove on the upper side, it means that just one of the holes can supply the oil to the crankshaft journal at all times, while the lower metal bearing will expose itself to damage unless the oil is sent to it.

In contrast to the genuine, the oil can circulate inside Maruha's main bearings because both of our upper and lower bearings have grooves that can send the oil to the 2 journal holes.
The grooves promote more oil circulation to the connecting rod bearing.

The genuine and genuine-shaped bearings
There is an oil groove in the upper bearing only.
One of the 2 holes in the crank journal can feed the oil.
Maruha Power Metal Bearing
The bearing ring groove helps the 2 holes send oil into the crankshaft.
It allows more oil flow to the conrod bearing.
Your engine operates at higher rev ranges and more centrifugal force is being generated.
It causes poor oil flow in the crankshaft journal.
However, our bearings can be fully operated with the grooves even in severe conditions.

Red arrows: the oil flow/ Blue arrows: the direction of the centrifugal force
Centrifugal force caused by high revolution drives the oil to flow back to the crank journal.
The connecting rod bearings are under a risk of being damaged unless the oil circulates inside the journal against the force.

2. Durable copper based alloy F112

The appearance of the small but high-powered engines has increased bearing loads.
Consequently, people longed for something instead of bearings with sintered alloy and aluminum bearing alloys that had been widely used but that could not work under the heavy loads.

Copper based alloy F112 used as main and connecting rod bearings of high-powered machines such as racing cars, heavy-duty trucks and large industrial machines is excellent at high speed and heavy loads.
The material gained popularity in the United States, that was the first country to spread high-powered engines. Furthermore, it was introduced in Europe too.

Although it takes a huge equipment cost to produce the alloy with high technology, why is F112 becoming popular in a lot of countries?
We will show you its structure and features comparing to a sintered alloy that is copper-based.

The celmet made of sintered copper lead alloy powder cannot withstand heavy loads.
The copper alloy powder bonds are weaker than F112 as the powder is sintered at lower temperatures than the copper melting point. It tells you the powder bonds are easy to break under high loads.

F112 consisted of the overlay metal and the copper based alloy on the backing steel plate has the copper alloy bonds formed vertically.
Some of them also spread from the main stems like branches.
The lead alloy acting as a lubricant disperses among the bonds.
Heavy loads pressuring vertically are hard to damage the F112 structures.

F112 has unique structures like stems and branches.
They bring this alloy outstanding performances in the load bearing and the seize resistance.

The copper based alloy F112 has superior corrosion resistance to the sintered alloy.
The overlay surfaces prevent both of them from getting damaged.
However, the sintered alloy is likely to become corroded after the overlay is worn out.

The lead that forms the lead bronze layers beneath the overlay surface has corroded towards the inside.
It causes the layers to become caves destroyed by the loads.

The sintered alloy corrosion advances because the lead bronze layers are arranged in rows.
In contrast, the dispersed lead of F112 can avoid the deep corrosion.

3. Surface-overlay plating

The cross-section of Maruha Power Metal Bearing

The overlay metal covers the bearing surface to enhance the oil absorption and the running-in lubrication.
Copper based alloy F112 has excellent load bearing capacity, but at the same time, it is worse in several performances like the surface performance, the oil absorption and the lubrication that are necessary to operate the bearing completely.

The overlay metal can improve these abilities and it prevents the seize damage caused by the shaft misalignment, the poor surfaces of the crankshaft and something in the oil.

4. You can choose from 3 sizes

With different size setup it is possible to get adequate clearances to maximize your bearing performances.

The genuine MIATA bearing has only one setup, Standard Size. It means that you need several sizes to have exact clearances.

Maruha has examined data on bearings comprehensively, including the genuine bearing's size.
We introduce you the 3-size bearings that can cover a range of frequent use. Our products meet the needs of many customers.

We have "Standard Bearing Kit" designed to take the middle of the baseline production allowances.

5. Introduction of the Standard Bearing Kit

- Size of Maruha Power Metal Bearing Line-

Main Bearing
Size Range
A 2.002-2.006mm
B 2.006-2.010mm
C 2.010-2.014mm

Connecting Rod Bearing
Size Range
A 1.500-1.504mm
B 1.504-1.508mm
C 1.508-1.512mm

6.Sales unit

You can buy our bearings from one set of the upper and lower bearings, which is the minimum unit for sale.
You can also order the units you need to complete the overhaul.

Main Bearing (Upper & Lower/unit)

Size Range
A 2.002-2.006mm
B 2.006-2.010mm
C 2.010-2.014mm

Connecting Rod Bearing (Upper & Lower/unit)

Size Range
A 1.500-1.504mm
B 1.504-1.508mm
C 1.508-1.512mm

6. Introduction of the Standard Bearing Kit

Maruha sells a Standard Bearing Kit designed as the mid size bearing, which is most-frequently used to take the middle ranges of the genuine production allowances.

10 Main Bearings/car
Kit Component
Ax1unit/ Bx3units/ Cx1unit
A: 2.002-2.006mm B: 2.006-2.010mm C: 2.010-2.014mm

8 Connecting Rod Bearings/car
Kit Component
Ax1unit/ Bx2units/ Cx1unit
A: 1.500-1.504mm B: 1.504-1.508mm C: 1.508-1.512mm

This kit is designed to be in the middle ranges by combining the upper and lower bearings.
For example, when you merge the upper A and the lower C, they form the mid size bearings, as well as when the upper and lower Bs are connected.
You can change these combinations as your preferences to pursue accuracy.

You can have your own original kits composed by the sizes you need. When you place a special order, let us know the essential information including which sizes and how many units you want.


Maruha Motors Co., Ltd.
Ushizuma 2095-6, Aoi-Ward
421- 2106 Shizuoka city, Shizuoka prefecture
TEL: 0081-54-294-0076
FAX: 0081-54-294-1312
E-mail: info@maruhamotors.co.jp