BUSH UPGRADES

▶ When faced with replacing bushes, upgrading is a tantalising proposition. Yet, consider that car manufacturers and their suppliers strike a balance between bush comfort, longevity, cost and stiffness. With upgrades, changing bush specifications is likely to sacrifice one quality for another. For example, in the pursuit for a slightly sharper handling and (possibly) longer bush life, you might select suspension bushes that possess a higher shore hardness than those fitted as standard. You could well achieve your aims but increased noise and vibration may be transmitted into the cabin, making the car more tiring to drive on long motorway runs but more engaging on country roads.

It is also worth considering that upgrading for upgrading's sake can be dangerous. Dependent on the vehicle, the standard bushes provide certain advantageous handling characteristics. As an example, a vehicle can be made less susceptible to change direction in heavy cross winds, by flex in the control arm bushes altering the suspension geometry sufficiently to compensate. Certain models also require bush movement to provide an inexpensive method of passive rear steering. Not understanding this and fitting harder bushes, therefore, is undesirable. A further issue occurs, when the lack of compliance in the harder bush transmits extra forces into the metal component, causing fatigue and subsequent fracturing. CM is not advising readers to avoid performance suspension bushes but to consider performance bush implementation carefully and consult a quality performance manufacturer for specific advice about your vehicle. You can then select the parts that will achieve your aims.

Interestingly, several aftermarket bush suppliers analyse how the original bushes fail and use the data to offer replacement parts that last longer. You could view these parts as upgraded but, because they do not enhance the car’s dynamic performance, it is unlikely that you will need to declare their fitment to your insurance company as a modification. An example is febi and MOOG’S front suspension bush for certain Volkswagen Group models, which boast more internal connections between the rubber core and the outer sleeve, instead of just two. The ‘HD’ range from MEYLE contains similar enhancements, although an interesting development from that brand includes slotted bushes for the BMW 5-, 6- and 7-Series rear aluminium suspension control arms. Officially, these suspension arms must be replaced but the MEYLEHD solution comprises slotted bushes that are precompressed within an installation sleeve and fitted using a dedicated tool, as pictured. The company highlights that the pre-compressed bushes makes them easier to install and reduces the chance of damaging the aluminium castings. When introduced in 2018, the company claimed that replacing the bushes offers more than a 90% saving, compared to the official recommended practice of replacing the complete control arms.