Skip to main content


Flywheel bolts are critical bolts used to fasten the flywheel to the crankshaft.

The flywheel looks like a steel or cast iron disc connected to the crankshaft, and its function is to absorb the kinetic energy by accumulating it and returning it during the vehicle’s motion.

In the case of cars with automatic transmission, the flywheel bolts tighten the connecting plate, or flexplate, so that the gears can automatically mesh and gear down.

Flywheel bolts usually are tightened to torque + angle.

They have an external driver head and no washer.

Although they are less complex than other critical bolts, the greater horsepower today is also in economy cars and the decreased number of cylinders demands these fastening elements to return always equal performance.

As they must never manifest loosening phenomena, they are equipped with a micro-encapsulated adhesive.

Cars with automatic transmission

tighten the flexplate


micro-encapsulated adhesive

Strength class

10.9 and 12.9


Flywheel bolts are the perfect solution to fasten the flywheel to the crankshaft.

These fasteners are usually small, compact, and cannot have very large heads.


Flywheel bolts are critical bolts that are part of the computation of those elements crucial for achieving engine performance.

#Brugola OEB

The Brugola OEB cylinder head bolts are the result of many years of experience and the highest attention paid to the unique and specific needs of each customer.
Every one of our fasteners comes up to the Total Quality and Zero Defects principles.
They must allocate the highest load possible for transmitting the power from the engine to the gearbox.

They must distribute the highest load possible to guarantee proper transmission of the power from the engine to the gearbox.

The main characteristics of flywheel bolts

The first distinctive element of flywheel bolts is the small space where they must be positioned.
Hence, these fasteners are usually small, compact, and without big heads.
The space limitations impact the design and construction stages and affect flywheel bolts‘ ability to obtain spectacular performances.

Whatever the space available is, flywheel bolts must distribute the highest load possible to guarantee the proper power transmission from the engine to the gearbox.
They are not required to have particular length or rectilinearity characteristics, and they are not subjected to extreme thermal stresses like what happens to cylinder head bolts.

However, they demand a particular amount of experience in their design and production since they are critical bolts enclosed in the analysis of those crucial elements for engine performance.

Flywheel bolts have strength classes and bespoke solutions

To best meet space requirements, in most cases, flywheel bolts have strength classes 10.9 and 12.9, and also customized classes with very narrow Rm ranges.

The trend is starting to also anticipate class 14.9, precisely as what is happening for the con rod bolts, which are also components that have to keep to small dimensions due to their role and the type of stresses to which they are subjected.

Nevertheless, rising in class exposes any bolt to the risk of embrittlement caused by hydrogen.
The flywheel bolts are the most exposed to this phenomenon, so it is necessary to consider this possibility.
From our point of view, this is one more reason to choose Brugola OEB’s know-how, which is very careful to prevent hydrogen-caused embrittlement starting in the bolt production stage.<
When you are looking for flywheel bolts or any other special or fastening component, Brugola OEB is a reliable partner for developing your component.

When you are looking for flywheel bolts or any other special or fastening component, Brugola OEB is a reliable partner for developing your component.

Why choose
Brugola OEB flywheel bolts

Brugola OEB is an outstanding partner for designing and making all types of critical bolts and other fastening elements in the automotive industry. We always put the same care and experience into every screw, bolt, fastener, or design piece to create a customized product that complies with the Total Quality and Zero Defects requirements.

Even though flywheel bolts may present less complexity than other critical bolts, we enforce the same consultancy process for these fasteners as well.

We are not simple makers. Instead, we follow the customer along the entire product life cycle, from the early design stages to the final result.

Thanks to the details indicated in the specifications, we support the customer in defining the best geometry and desired flywheel bolts’ mechanical properties, as we do for all the other fastening elements.

Thanks to our in-house software program, we can perform simulations on the behavior of the flywheel bolts and get reliable and concrete data starting from the pre-production stage.
During execution, on the other hand, we place considerable importance on preparing the wires.
We do not adopt chemical pickling to clean and lubricate them before starting the processing, instead, we use sandblasting and a special coating that guarantees a total absence of hydrogen in the material.

The attention we pay to research and development, as well as the innovative spirit that has set us apart from the others since our establishment, allow us to keep up with the last innovations and offer solutions that tangibly resolve the main problems in the fastening elements sector in the automotive industry.

We are at the side of our customers for any request, from the simplest to the most challenging.