The transformation from Austin to Rover Metro/100 was an engineering triumph. As well as the new K-Series engine, it received a thorough suspension upgrade.
This was a remarkable change – a few very clever and considered updates turned the car into a dynamic class-leader… Here’s the original press release and some background.
I didn’t do the Rover Metro (R6) press kit, but here it is as we released it in May 1990. I think there was a deliberate policy from Rover of not going into huge detail on the suspension changes, because that might have highlighted the compromises forced upon the original Austin Metro (LC8) by using carryover Mini (ADO15) front suspension bits.
I suspect that any cost-saving achieved by doing that was seriously negated by the need for an expensive H-I split dual line brakes with four-pot front calipers…
The design of the chassis systems on the new Metro is fundamentally similar to the existing models. However, significant changes have taken place in the Hydragas suspension system, and the new front suspension design features anti-dive geometry.
The braking system and steering have also seen many detailed design changes to improve efficiency and overall ‘feel’ in line with the suspension change. ‘Torque Axis’ engine mounts are a major feature change allied to the new front end structure and K Series installation.
Origins of the Hydragas System
Hydragas is an interconnected suspension system designed by Dr Alex Moulton. The challenge in the 1960s was to create a ‘big car ride’ whilst maintaining the legendary handling of the then recently introduced Mini. The international rally winning Mini Coopers were fitted with ‘Hydrolastic’, the first of the interconnected suspension systems.
Ongoing development through the 1100, 1800 and later Minis resulted in the birth of Hydragas.
The current concept takes Metro a stage further with front to rear interconnection through plastic pipes with a water-based fluid hermetically sealed in diaphragm displacers – one at each wheel. The displacement of the fluid provides the damping and the sealed nitrogen, the springing.
Hydragas has been proven over many years on millions of cars and is an extremely efficient and compact system. Lack of intrusion into boot and under-bonnet space is a major plus for Metro. Changes to Hydragas for the new Metro Hydragas uses hydraulic displacers at each wheel. In the new Metro application these units have been interconnected front to rear.
The interconnection gives a controlled ‘bogie action to the suspension which reacts to and absorbs road irregularities much more in the manner of a large car than the previous Metro. The flatter ride platform is in marked contrast to the existing car and handling also benefits – particularly in respect of wheel control on high speed bumpy cornering. Interconnection is by plastic pipes mounted under the floor.
A sports suspension version is fitted to the GTi 16v Metro (top). Sharper response is provided by front and rear anti-roll bars and additional external shock absorbers at the front.
Other features of all new Metros include
- Anti-dive, anti-lift wishbone geometry at the front.
- Optimised camber control in roll for good bump steer characteristics.
- Front and rear subframes with rubber mountings for good road noise isolation.
The new Metro uses a rack and pinion steering system across the model range.
Ratios have been carefully chosen to reflect Metro’s small car market positioning giving the best compromise between steering effort and sensitivity to steering inputs. With its high percentage of female buyers, the small car sector places particular importance on steering effort for in-town manoeuvring and parking.
All models except GTa and GTi have 3.7 turns lock to lock with a revised ‘quicker’ ratio of 3.3 on the sporting GTa and GTi.
Turning circles are 9.87m (32.4 ft) on all models except GTa and GTi which have a turning circle of 10.71m (35.1 ft).
As a fundamental part of the changes to Metro’s driving position, the steering column angle has been lowered.
Engineering design changes have resulted in a totally new column incorporating collapse and energy absorption sections for added safety.
The new Metro incorporates the Rover Safety Steering Wheel concept first used on the new Rover 200 Series.
A joint development between Rover, the Transport and Road Research Laboratory (TRRL) and Sheller Clifford – Rover’s steering wheel supplier – this safety wheel has a layer of energy absorbing foam within the centre boss which reduces the acceleration level of a driver’s head under impact conditions. The securing nut, holding wheel to column, is located deep into the wheel boss behind the foam padding.
This design dramatically reduces the severity of facial injuries caused by contact with the wheel in an accident.
The steering column cowl and bracketry have been carefully designed to eliminate rattles and improve the NVH performance of those steering components mounted inside the vehicle.
The existing Metro brake system has received much acclaim for its good pedal feel, stopping power and optimised servo action.
The new Metro carries forward the same basic layout with an evolution into a larger diameter solid front disc and single piston caliper. This state-of-the-art system is easier and more cost effective to maintain.
The brake pipe layout is simplified by the use of a diagonal split for secondary braking rather than the H-I split used on the existing Metro.
New Pedal Positions
The major revisions to the Metro driving position are carried through to the foot pedal layout. All three pedals are moved further outboard, thereby reducing the offset caused by the intrusion of the existing front wheelarch.
The clutch pedal ratio has been modified along with the throttle pedal to suit the characteristics of the new K-Series engine.
- I was there : Austin Maestro launch advert, January 1983 - 3 March 2023
- The cars : Rover Metro/100 suspension details - 4 September 2022
- I was there : Selling the Rover SD1’s rear suspension - 29 August 2022