These bushes fit all E46 3 series BMW’s and are recommended for those who have installed underside reinforcement plates in addition to comprehensive topside reinforcements to their E46 chassis.
Factory rubber and polyurethane bushes isolate the subframe beneath the chassis allowing undesirable twisting and lateral movements due to body roll, lateral G-forces & drive line forces. As the subframe is used to mount the upper and lower control arms, sway bars and house the diff, these movements result in changing suspension geometry which can cause instability at high speeds and isolate stresses to individual subframe mounts.
By hard mounting the subframe directly to the chassis, these unwanted movements are eliminated creating a back end that provides greater feedback while also being more predictable and responsive to driver inputs which is critical when approaching the limits of grip. Hard mounting with solid bushings also lend the sub-frames rigidity between the 4 rear mounting points much like a strut brace between shock towers. This results in a localised increase in rigidity however, impulsive drive line forces and now less dampened resulting in higher peak stresses which can increase the rate of failure in areas transferring stress between the subframe mounts and chassis rails. For this reason, solid subframe bushes are only recommended for E46’s with our extensive topside RACP reinforcement kits.
In addition to the advantages of using an aluminium bush over rubber or polyurethane, raising the subframe relative to the chassis brings the roll centre closer to the centre of gravity reducing the induced roll moment under the same cornering G-forces. This results in reduced body roll and weight transfer providing greater grip with the road providing stability and a sense of a more agile vehicle.
Every components fastened to the subframe such as the diff, control arms and sway bar are isolated by bushings of their own resulting in a negligible increase in NVH. CMP Auto Engineering recommends these bushes to anyone who intends to take their vehicle to the track or drive aggressively under road conditions.
Note: For vehicle running factory ride height, the change in roll centre does alter suspension geometry to the point that adjustable camber arms are required to bring rear camber within factory specs.