[B21]

The E89 suffers from rear wheel steer caused by the geometry of the rear wheels moving from toe in to toe out..as soon as rear toe points out stability is compromised with unpredictability..as you lift off then toe angle changes again..

The more power, the more aggressively applied the worse the problem…it’s an issue in all aspects of handling…other BMW guys have recognised this and almost all pre F series cars have solutions of varying solutions to this issue inherent in rear trailing arm designs..

When I tried to get the steering geometry set up we found that the toe in couldn’t be set to perfection due to limitations in adjustment of the stock rear trailing arm to chassis brackets.

In addition they observed that the trailing arm bushes fitted only a year earlier were showing signs of wear…

The E89 rear suspension is a complete copy of the E85/86 except that certain dimensions are altered as a result of track width changes.

The E85 boys have been changing their RTABs for a long time with all sorts of versions being used such stock, polyurethane and even roller bearings.

The issue for the E89 as well is that the whole rear wheel geometry and stability rests on the integrity of the bush and its relationship to the arm and bracket.

The problem is that with 400 BHP tugging at the bushes they deform under load and wear..in both cases the toe in fa tor changes..going to toe out..analogous to dynamic and unmanageable rear wheel steering.

To get round these issues I’ve bought some chunkier RTAB mounting plates that bolt to the chassis and have much greater adjustability.

To get round the distortion that happens to the RTAB there are various solutions..needle / roller bearings, polyurethane bushes and in this case a much uprated rubber based bush but with a focus on stability whilst still avoiding NVH induced issues.

Hardrace make these bushes for a wide variety of cars and other suspension related bushes..as well as needle roller solutions if you can cope with NVH.

I’ve got the bushes for the other linkages , 2 per side.

Since all these bushes during their installation process will affect the geometry I plan to get these done by the shop that then does the geometry adjustment..

Pictures show the stock bushes alongside their uprated cousins..

This set cost around £300 so not a cheap solution plus another £100 ish for the chunky brackets..