Manufacturing & Assembly, Product Expertise

Optimised Fasteners for Automotive Wheels

Optimas | September 12, 2023

The automotive industry continues to grow, and in particular so does the automotive wheel market. The global automotive wheel market size was valued at $31.4 billion in 2021 and is expected to register a compound annual growth rate (CAGR) of 6.10% from 2023-2028, so it’s clear the market is continuing to drive onwards.

Fastener Demand

torque gun

Torque limited wheel gun

Automotive wheel systems  predominately use wheel bolts and wheel nuts, and these fasteners are subject to high-quality design, manufacture and assembly. These fasteners need to meet the highest demands on performance and longevity.

Security is an important aspect for automotive wheel fasteners. Anti-theft designs of these fasteners ensure that it is more difficult for criminals to remove wheels or tyres off vehicles due to wheel bolts only being tightened with specialist tools.

All fasteners across an automotive build are required to meet high tolerance demands, bearing loads between 65-90% of their yield strength so they don’t loosen in their application, or worse, break. Automotive fasteners also need to be able to withstand significant vibration to effectively hold the car together. For automotive wheels, failure to use incorrect or insufficient quality wheel bolts or nuts may cause the wheel to loosen, tire pressure to be lost and potentially loss of vehicle control which could result to personal injury.

calibrated torque wrench

Calibrated torque wrench

Automotive wheel fasteners also need to be highly corrosion resistant to withstand environmental conditions, like extreme heat and cold, salt from gritted roads, as well as chemicals used in processes like car washing. Using fasteners that are PPAP 3 certified, and made of materials like stainless steel, titanium and treated aluminium alloys, can increase a vehicle’s durability by ensuring its key components are optimised for different environments and temperatures.

In addition to those factors, ensuring the wheel is as lightweight as possible is key for any automotive build. A surplus weight increase by fasteners can lead to more harmful emissions due to less fuel efficiency, but also, they will add pressure on the vehicles tyres which results in further safety concerns.

When Fasteners Fail

Through improper tightening, unsuitable processes or even insufficient tests for fasteners, there are a range of factors that can result in fastener failure and lead to huge safety implications.

Damaged wheel bolts

Damaged wheel bolts

A recent study on the automotive industry in the United States found that 23% of service problems were attributed to loosening threaded fasteners and 12% of new vehicles have experienced substandard tightness of their thread fasteners.

Therefore, it is extremely important automotive wheel fasteners are tightened to the specified torque for the fastener and application. Wheel bolts on cars should always be tightened using calibrated specialised tools such as torque limited air wrenches and always checked by using a torque wrench, and never by judgement alone. Mounting wheel bolts should only begin by hand to avoid misalignment of the fastener and damage to its seat, but the correct tools need to be used to control the tightening torque.

Damaged wheel bolt holes

Broken wheel nuts

In some cases of failures, the wrong type of fastener can be the issue for the vehicle’s failure. If the bolts are too long, they can potentially interfere with other parts, which is fraught with wheel locking. It’s also vital to use the correct type of fastener with the required mount. For example, use of conical seat fasteners in the wheels with spherical mounting seats and vice versa leads to misalignment of the wheel to its rotation axis, causing the threaded connection to loosen.

The production of fasteners can also create failures. Hydrogen embrittlement occurs when fasteners become brittle as a result of the introduction and diffusion of hydrogen into the material. This can substantially increase the stress of applied forces within the base metal causing the damage to manifest as a reduction in ductility in the elastic range, reduction in the yield and ultimate strength of the fastener. The hydrogen damage can be immediate or sometimes delayed, meaning failures can occur before or after an embrittled part enters service. Embrittled components have been known to crack or “pop on the shelf” before being assembled or even used, therefore demonstrating how important it is to have the correct production methods for your fasteners.

The Benefits of Cold forming Wheel Bolts

damaged wheel bolt hole

Damaged wheel bolt hole

Cold forming begins with a wire or rod of metal, and it progressively forms the desired shape without material removal. This becomes a cost-effective option due to the minimal waste from the manufacturing process. Furthermore, cold forming can enhance the mechanical properties of the material, making it stronger and more durable, which is crucial for wheel bolts that need to withstand high loads and vibrations.

The cold forming process offers excellent dimensional accuracy at high-speed production rates, ensuring that the wheel bolt is consistent in size and shape, whilst meeting the demands of the automotive industry. This precision is vital for proper wheel assembly and safety.

In summary, cold forming is an advantageous manufacturing method for wheel bolts because it combines efficiency, precision, and material optimization, resulting in cost-effective, high-quality components that meet the stringent safety requirements of the automotive industry.

Optimas: Providing you with Engineering and Quality Solutions

For automotive manufacturers, Optimas can provide expert engineering services to ensure their automotive builds don’t encounter these potential issues and provide them with the quality fasteners they need for their vehicles.

To achieve a “best-in-class” product range of fasteners and components, our work goes beyond identifying the best suppliers. We conduct a rigorous qualification process to ensure suppliers can manufacture high-quality parts at the volumes you need, when you need them. We work with our suppliers to continuously improve their product performance and capabilities to support you in every aspect of your supply chain.

Plus, our dedicated team of fastener engineers across the world can work on a project basis or on-site with your engineering department. This close relationship allows us to play an active role from product development to assembly line where quality and productivity matter most. We focus on saving you money while maintaining or improving quality.

Optimas are also the only manufacturer with cold-form facilities on both sides of the Atlantic. By sourcing your nuts, bolts and screws locally and onshoring your supply, lead times can be significantly reduced from PO to delivery, and simplified transportation provides you with a more sustainable and efficient supply chain.

For efficiency, quality and security, partner with Optimas for your fasteners and let us de-risk your supply chain.