PMM JUNE 2011 45� READERLINK 020

The Discovery channelThe experts at SuperPro claim they’ve found a solution to an issue with LandRover Discovery Series 3 front lower control arm bushes. We find out more.

Steering & Suspension

In its initial stages, Land Rover’sengineers faced some challenges indesigning this luxury vehicle whichneeded to offer outstanding on-road

performance whilst maintaining a reputationfor off-road capability. Suspension bushesplay a part in the solution – with the frontlower control arm bushes required to offercompliance for comfort and off-roadarticulation whilst maintaining steeringgeometry for sharp and precise handling.

Land Rover’s design employs a‘hydraulic’ bush for the rear position on thisarm – so, even though at visual inspection thebush looks like any other rubber bush, it is infact filled with oil.

This design of this bush is vulnerable tofailure – often as a result of impacts. There is atendency amongst the drivers of 4x4’s such asthe Discovery to believe that as an ‘off-roader’it can cope with speed bumps and mountingkerbs at a pace not attempted in a ‘normal’ car.In addition, the deterioration of the rubber

outer casing can, in time, allow leaks of thehydraulic fluid to develop. The net result isexcessive movement in the lower arm.

The new bush kit from SuperPro includessome unique design features to replicate theflexibility of the original hydraulic bush,whilst utilising SuperPro materials’ durabilityand high levels of resilience. Moreimportantly, SuperPro’s unique materialformula holds very high rates of tear strengthand elongation compared to rubber, regardlessof temperature. This has big implications forcold climates and means the SuperPro kit willkeep these high levels for longer.

The SuperPro engineers were able to drawon substantial experience of similar bushes oncars from other manufacturers and, havingcarried out extensive on car evaluation,selected an innovative design with threepieces of polyurethane, including a centralsection with deep cutaway sections in thepolyurethane. These ‘voids’ are key inallowing the material the opportunity to flexand move in line with Land Rover’s originalparameters and not creating noise vibrationand harshness. The materials’ resilienceensures that the suspension regains itsalignment, and because it delivers thiswithout the hydraulic features of the original,is less susceptible to damage and wear. Incommon with all SuperPro products, these

bushes are supplied with a three year/36,000mile warranty regardless of how cold it gets.

To request more details aboutSuperPro’s range of replacementbushes circle 118

■ Care must be taken when removing the originalhydraulic bush as it will not cleanly press out. ■ Drill a hole in the rubber section of the bush and allowthe oil to drain out. ■ Carefully heat the steel inner crush tube until thebonding to the rubber has broken and the tube can bepushed out. Heat can then be gently applied to theoutside of the control arm until the rubber bond with theouter steel shell has been broken and the remainingrubber can be pushed out. It is not recommended to‘burn out’ the old bush.■ If using an oxy-acetylene torch for this process – it isimportant to work in a well ventilated area and follow allrelevant health & safety procedures. ■ Use a hacksaw to carefully cut the steel outer shelland then remove with a chisel. Make sure that the innerfaces of the housing are clean and free of sharp edges.■ The new bushes are assembled as per the diagram(pictured below, left) – it is essential that plenty of thelubricant supplied is used on the inner bore of thebushes before the new steel sleeve is inserted.■ The arm should be reassembled into the car using theoriginal land Rover Torque settings – it is recommendedto recheck these after 1,000 miles or 1 month. And, incommon with all suspension work the car should have afull wheel alignment.

Bush installation advice

Original Land Rover arm with bushes removed – the oil filled bush is on the left The assembled arm looks like this

Front control arm front bush

Front control arm rear bush (hydraulicreplacement)

This diagram shows how the new bushes are assembled

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