WA Branch Technical Meeting - 9 June 2025 A ‘Cold Case’ Analysis – Morris Marina Front Suspension Failure

Source: Dr Steve Algie – S H Algie & Associates Pty Ltd

Dr Steve Algie described the retrospective failure analysis he had conducted into the root cause of a near-fatal car crash in which he had been involved.

The single-vehicle rollover occurred in 1981 in the UK, while Steve was driving a rented Morris Marina. The analysis was made possible by his chance rediscovery of a roll of unprinted black and white film, with clear photographs of damaged components from the wrecked car.

Steve was hospitalised with a concussion and has no memory of the event, other than that the steering had suddenly failed. However, his wife had recorded in her diary that while travelling on the A19 at 70 mph (110 km/h), the car suddenly veered right, then left, spun 180 degrees to the right, struck the median strip, rolled 360 degrees, and landed upright on the opposite carriageway. It was sheer luck that no other vehicles were involved in the crash, as the consequences could have been fatal for multiple parties.

The root cause of the crash was never determined at the time, but more than four decades later, prompted by the availability of the photographs, Steve reopened the "cold case." He applied a range of mechanical and materials engineering principles to reconstruct the likely sequence of mechanical failures that led to the crash.

The photographs showed that the front lower suspension arm had fractured through tie rod mounting hole. This was the first point of failure, and physical modelling with plasticine showed how the subsequent complex deformations of the front suspension components observable in the photographs had occurred in sequence during of the various phases of the rollover. This sequence was confirmed by estimates of yield, work hardening and ultimate strength properties of the materials likely to have been used in the components.

Central to the analysis was the Morris Marina’s front suspension design, which used torsion bars and elastomeric bearings based the 1948 Morris Minor. The vehicle’s lower front suspension arms are a critical component but were apparently minimally designed for the relatively low stresses to which they subject in normal circumstances. However, as the photographs clearly show, this was the point of initial failure and a weak point in the design

The analysis considered how fatigue failure could have originated at the hole for the tie rod pin. By considering materials properties and road forces, Steve demonstrated that stresses from pothole impacts, or heavy braking could lead to crack propagation by low-cycle fatigue, making the front arm vulnerable to failure under ordinary steering forces. This created a "hairtrigger" situation, as the suspension would have continued to function apparently normally until the moment of final fracture, with no external warning to the driver of impending catastrophic steering failure.

Information now accessible online confirms that tie rod issues are a known weak point in the Morris Marina, though at the time not widely acknowledged as a serious failure risk.

Reflecting on the context of the early 1980s, Dr Algie noted that failure analysis was not routinely conducted for consumer vehicle accidents at the time, and the UK regulations around vehicle design and safety were far more relaxed than today’s standards. Even seat belts in the back were not mandatory in new cars until 1987.

The Morris Marina had a reputation for poor structural integrity, and its design reflected cost-cutting measures and outdated engineering decisions. Indeed, the Morris Marina now makes regular appearances in online lists and videos of ‘the worst cars ever produced’!

In summary, in terms of Failure Mode, Effects and Criticality Analysis, the failure mode of the front suspension arm was not just theoretically possible, but demonstrably real and potentially catastrophic. Exacerbating the situation, hidden and progressive crack propagation would not necessarily have been revealed in regular servicing. Thus, the design would surely not be acceptable today due to its susceptibility to a single point of failure, lack of redundancy, and undetectability of impending failure under standard maintenance practices.