Don't Be Vague - Take Control
In answer to the questions raised in recent issues of the Stag magazine concerning the Stag steering and handling problems, I can advise you as follows:
There is nothing basically wrong with the power steering system even though there is a bit of a dead band in the straight ahead position. It was typically light and unprogressive as was the fashion in luxury cars of the 1960/70 era, equipped with solid rear axle assemblies, which gave good track alignment at the expense of poor traction on anything but the best of roads.
The problem lies in the uncontrolled and contradictory steering inputs from the poorly located trailing arms of the rear suspension fitted to the Stag and it's predecessor, the Triumph 2000. As the suspension tries to cope with varying road conditions on the move, such as bumps, dips, cambers and side loads, each wheel independently deviates from the theoretically correct and stable toe-in setting that it has in a static condition. This subsequently degrades the natural self-centring and aligning effect of the strongly castored front suspension and is not easily countered by the feel-less steering. The uncontrolled variations of tracking from toe-in, through neutral, to toe-out under hard cornering, also produces the familiar understeer to oversteer switch and accentuates the spline lock/unlock twitch effect.
The solution to the problem is to introduce better track control to the basically correct suspension geometry, and there are to my knowledge only two effective ways to do it.
- Replace all the suspension bushes with the stiffest, most unforgiving type you can find, a la competition cars. Okay if you can stand the noise, vibration and harshness - I couldn't.
- Keep the standard rubber bushes and their refinement and add specially designed control links ('Traktoe Bars' I call them) to maintain consistent rear wheel tracking and alignment and 'hey presto' you have 'hands-off' straight-line steering and predictable handling - I like it!
I have developed and used such a system on my car for many years after studying the suspension designs of most modern rear wheel drive vehicles and I can fine-tune it to suit individual tastes by small adjustments to the basic settings.
A similar system based on my design was illustrated on page 16 of the August (2002) Stag magazine and was displayed at the SOC National Weekend.
I hope the foregoing helps clarify matters and look forward to seeing responses especially from any other experienced engineers.
I have also developed a simple add-on anti-roll bar system to further enhance the above improvements and reduce the bouncy nodding dog and diagonal pitching traits of this type of suspension.
Gordon J. Timms
Warwickshire Area Co-ordinator - Stag Owners Club