R&D combats OE design flaw


Poor driving, uneven road surfaces and debris have their part to play in wearing out chassis parts, but by using quality components, checking alignment after repairs and providing a free spring health check for customers, you can play your part in promoting longevity.


From the car manufacturers’ continuous drive for lightweight components, springs new challenges inspired by inherent flaws in component design or manufacture, such as bush ejection from the latest generation of aluminium control arms. The use of such arms was initiated by German manufacturers and has become a more common trend across the European market. As these vehicles become older, a much higher control arm replacement frequency has been reported, with bush ejection noted as a major concern in 95% of cases.
Jonathan Allen, Regional Marketing Manager at Federal-Mogul Motorparts, believes that the company’s MOOG brand has found a solution: “Bush quality is a major factor when it comes to bush ejection; MOOG has combated reported issues by altering manufacturing and testing processes to help optimise four key factors: press-in tightening rate (PTR), press-in method, material hardness and surface roughness.”
The manufacturer has refined the PTR and press-in method to ensure the pressing direction is perfectly parallel to the bore axis, enabling optimised ejection forces. Material hardness of the bush and outer sleeve can also impact ejection force. “MOOG is the only supplier to test both the control arm and bush in-situ,” Allen continues, “using a maximum theoretical force. Applying approximately 600kg of pressure through the axial load on the inner or outer sleeve of a bush ensures that all aluminium arms are tested and approved to MOOG’s OE-standards, providing an extended life cycle.”
Aluminium control arm failure issues offer a range of symptoms, including excess noise and vibration, which can negatively impact driver comfort and ultimately jeopardise passenger safety. Cracked and torn rubber bushes are a common problem, as is rubber-metal separation, often aggravated by the usage and application of the chemical bonding agent.
The use of aluminium control arms will become more commonplace as the European market turns to aluminium components for advanced multi-link suspension designs, which will increase the demand for part replacement. The ability to up-sell a better solution, rather than just a like-for-like replacement, will benefit both workshops and customers, says Allen. “Given the choice, most people are willing to spend a little bit extra for a better product, if they are made aware of the benefits.”

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