WHEEL BOLTS AND NUTS
Level C indicates that in the case of the bolt breaking, no important inconveniences are created; for example, this is the case of bolts that fasten the glove box.
Level B, on the other hand, indicates an inconvenience of medium extent, which would be a bolt that creates a forced stop of the vehicle if it breaks.
Level A, indicates a fastener that if it breaks, may jeopardise the safety of the user, causing injuries to the person or even be life-threatening. Wheel bolts and nuts belong precisely to this last safety level, so they require maximum quality in their production.
The Brugola OEB cylinder head bolts are the result of many years of experience and utmost attention paid to the unique and specific needs of every customer. Every fastener that we produce comes up to the Total Quality and Zero Defects principles.
Since they are safety bolts, they follow a production cycle totally different from the other types of bolt.
The main characteristics of the wheel bolts and nuts
As they are wheel fastening elements, the wheel bolts and nuts are fasteners of primary importance for every vehicle. . They are made with specific safety characteristics.
Since they are safety bolts, they follow a production cycle totally different from the other types of bolt. The wire arrives at the sampling already branded as for a safety component only, and the product must pass exhaustive tests to be able to be approved and officially put into production.
In addition to the not to be ignored safety aspect, the attention paid to the wheel nuts and bolts in recent years began to also focus on appearance. With the application of alloy rims, increasingly requested on cars, the wheel bolts and nuts have become visible. Therefore, several solutions have been developed to make these components aesthetically appealing, such as application of plastic or stainless steel caps, or using dedicated technical-aesthetic coatings.
The tendency to expose these components led to requiring better performing corrosion resistance characteristics, as well as resistance tests on the acids used to wash the rims. Although not strictly regarding safety, this test also influences the final verdict. In fact, the bolts and nuts can be validated for mass production only if they are able to pass all the tests.
On the other hand, the corrosion resistance test follows a totally different procedure. The bolts and nuts are placed in a closed chamber saturated with a saline mist, a highly corrosive solution. In these conditions, they must hold out at least 600 hours (24 days) without showing the minimum sign of corrosion.
All wheel bolt and nut tests must be conducted in the sampling stage. Brugola OEB creates the component, carries out the tests and uploads the results in the customer’s quality system. At the same time, we send the customer other pieces on which it can independently conduct the tests performed by the manufacturer in order to confirm suitability. Only wheel nuts and bolts marked as “approved” are put into production. If a bolt is “approved with reservation” or “not approved!”, this means that it did not pass all the tests on cross-examination and therefore must be re-sampled to once again be subject to the same tests.
Once the wheel bolts and nuts are approved, the OEM conducts additional long-term tests by mounting the fasteners on some of its vehicles and making them go round for 100,000 km, each in different parts of the world. These dynamic tests on the vehicle, accompanied by a progressive check of the tightening of the wheel bolt and nut, serve to check the behaviour of the elements during real driving over a long period, in different weather and terrain conditions. In order to pass these last test as well, the wheel bolts and nuts must not in any way become damaged or loosened. It is only at that point that actual production can commence.
Thanks to its experience in designing and making automotive fasteners, Brugola OEB is a reliable partner also for safety components. We produce approximately 60 million wheel bolts and nuts a year and, considering that every vehicle requires 20 of these elements, with these figures we equip about 3 million vehicles.
Our company is extremely thorough in conducting the test necessary to approve production of the requested wheel bolts and nuts. We usually select 100% of the bolts we produce by using automatic machinery, and this applies even more to the safety elements that, as we have seen, require a precise and scrupulous procedure in order to move on from sampling to production.
Precisely to guarantee the anti-corrosion characteristics required can we finish the wheel bolts and nuts with about 400 types of coating, that is, all those we have encoded in our system.
All of our bolts also have corrosion resistance specifications, considering that the vehicle is means of transportation for the most part exposed to atmospheric agents. A bolt located inside the engine certainly has critical characteristics, especially from the mechanical, and not so much the corrosion, viewpoint. The attention we give to this aspect is therefore even more marked in making the wheel bolts and nuts, where the risk of corrosion in greater due to the more external position of these elements.
These can be grouped into four macro coating families, each with its own specifications: hardening and tempering, phosphated, laminar zinc and nickel zinc. We therefore also study the type of coating most suitable for obtaining a custom-made product and Total Quality for each wheel bolt and nut.