Skip to main content


Con rod bolts are critical fasteners used for tightening con rod caps, and they connect the con rod to the crankshaft.

They are normally tightened to torque + angle, have external driver heads, and no washer.

There are different types of con rod bolts, for example, unloaded or ground. In most cases, they are phosphatized and greased.

Furthermore, there are two for each cylinder, crucial for the engine’s efficiency.

Normally, the lower the overall weight of the bolts inside a vehicle, the higher will be its performance.

Precisely due to their role and position in the engine, con rod bolts can be subject to the customer’s request to remove a few millimeters of material by turning the shank after they are cold forged.

The purpose of this intervention is to decrease the weight and to improve the engine’s performance, a practice widely used above all in the racing area or on very high-performance vehicles.

Tailor made

Turning of the shank after cold forging

Moving components

low inertia while maintaining a good performance level

Double tightening

For a more constant distribution of the axial load


Con rod bolts are critical fasteners used for tightening con rod caps, and connecting the con rod to the crankshaft.


Con rod bolts are normally tightened to torque + angle, have external driver heads, and no washer.

#Brugola OEB

The Brugola OEB con rod bolts are the result of many years of experience and the utmost attention paid to the unique and specific needs of every customer.
Every one of our fasteners comes up to the Total Quality and Zero Defects principles.
The characteristic is that of moving components as they are pulled along with each revolution of the engine.

The main characteristic is being moving components, because they are pulled along with every engine revolution.

The main characteristics of cylinder head bolts

Different attributes make con rod bolts critical fasteners inside the engine. One of these is double tightening, which guarantees a consistent axial load distribution.
In fact, during the engine’s production cycle, the con rod bolts must be tightened twice in the plastic field, just like the main bearing cap bolts.
This means that during tightening the bolt is drawn beyond the limit that it can guarantee in terms of elasticity, and thus it experiences a plastic deformation. Once unscrewed, the bolt will have a different appearance than before, slightly longer.
Con rod bolts are critical also because they are among the most highly stressed bolts of the engine.
First of all, they are subjected to the same stresses as the cylinder head bolts, that is to say, the thermal expansions due to the combustions in the engine’s combustion chamber.
The piston connected to the con rod releases each burst onto this component and, as a result, onto the con rod bolts.

But that’s not all. Con rod bolts are subjected to three-dimensional forces. Whereas the main bearing and head (and therefore their respective bolts) are subjected to a typically axial task, the con rod carries out both a piston up and down movement and a rotary movement of the camshaft.

This gives rise to the most peculiar characteristic of the con rod bolts: moving components pulled along with every engine revolution.
These extreme stresses reveal the extreme importance of con rod bolts.
They must be small fasteners to get low inertia while maintaining an excellent performance level in racing or special power vehicles. Although they are minute, they must be strong enough to prevent the risk of breakage, upon penalty of damage to the engine.

Con rod bolts strength and location improvements 

As we have seen, con rod bolts are small parts, but with an important role and many responsibilities that require extreme resistance.
This is why con rod bolts are above all made in strength classes 10.9 and 12.9. 
Recently, class 14.9 is starting to be taken into consideration, like what is happening for the flywheel bolts.
However, rising in class may conceal a snag, because the bolts may be even more susceptible to hazards such as embrittlement caused by hydrogen.
The advantage of con rod bolts concerning this possibility resides in their location inside the engine, not in contact with rainwater and atmospheric agents that might trigger this process.
Furthermore, the Brugola OEB production method is attentive to preventing the presence of this phenomenon upstream, as certified by a joint study with a prestigious Italian university, with a view of supplying the customer critical fasteners, and therefore con rod bolts as well, which comply with the Total Quality principle.

Why choose
Brugola OEB con rod bolts

Brugola OEB con rod bolts are the result of many, many years of experience in the critical fasteners sector.

This relies on both the professionalism that distinguishes us and our long-lasting collaboration with the major players in the automotive industry.

We control 100% of the bolts of our production, including the con rod bolts, to pursue the Zero Defects goal.

The actual making of the con rod screws is inserted into a thorough consultancy process that starts from the customer’s specifications. Thanks to the information received, including basic parameters, dimensions, and materials, we can design custom cod rod bolts and perform specific analyses on the behavior of the bolt in various situations.

The proprietary software with which we perform the simulation tests on all the bolts we produce was created precisely for designing con rod bolts, under the special forces to which they are subjected.

In this way, customers will have available an overview of how the con rod bolts required will behave (also considering the double tightening variable) even before they go into production.