TOP MOUNTS
You may be tempted to save money by not renewing the top-mount but, should yours be of the rubber/metal design, not doing so could be a false economy. Modern top-mounts play an ancillary role to cushion noise and vibration, but they also serve several safety functions. As many mounts incorporate a steering pivot bearing (as pictured), they also influence steering behaviour and wheel alignment. Like dampers, they deteriorate over time. Not only do they support the weight of the vehicle, but they also move continually. Delphi Technologies, for example, told CM that up to 1750 movements can occur in only a mile of normal driving, a factor exacerbated by traversing potholes, bumps and kerbs injudiciously. Like dampers and springs, they are also affected by environmental influences, such as humidity, road salt and temperature changes.
When you dismantle the strut, it is wise to replace the top-mounts regardless of their condition, to save you having to do the job twice. They tend not to be expensive. Clunks that are heard while driving over bumps, or even low-speed squeaks, are more obvious examples – but be wary that you may blame uneven tyre wear, annoying vibrations, or the steering not self-centring promptly, on other components, when the top-mount is at fault. As with springs and dampers, replace top-mounts in axle pairs.