top of page

The Series IV – A Seven for the Seventies

By John Watson


Traditionally Lotus Components, the race car manufacturing arm of the Group Lotus, had made the Seven to help pay the overheads. Making and selling race cars meant inconsistent cash flow as the seasonal market for competition cars meant quiet periods. Compared with the Series Two model, the Series Three had not been a money earner for the manufacturer, in fact it is said that Components had lost over £100 on each one sold. Despite this, the model had still effectively contributed to the overheads.

Mike Warner, the new Chief Executive of Lotus Components Ltd., had been persuaded to rejoin the group after a short period ‘doing his own thing’. With Mike came the cast aluminium wheels which Lotus dubbed ‘Brand Lotus’. Mike’s task was to reduce the losses that were being made. At the time the other models being produced by the company included the Type 59 Formula 3 and Type 61 Formula Ford Cars.


So again the Seven was under threat; either production ceased or a version that was cheaper to produce and more marketable was designed. At an early stage it was decided that the key to success was going to be cost and volume. The main area where money could be saved was the aluminium clad tubular chassis being made by Arch Motors. The Elan chassis made of folded mild steel sheet cost half the money of the mild steel tubular item made for the Series Three Seven.

The Very different Series IV chassis


In the event it was decided to design an entirely new car. Warner saw that, as far as marketing was concerned, there were two main areas where inroads could be made. At home the Seven was to be conceived as Lotuses entry-level car. By making it more civilised and slightly more roomy, the MG Midget, Austin Healey Sprite, Triumph Spitfire market could be targeted and the young well-healed drivers of the day could achieve their desire to drive something different on a daily basis. In addition the old Series Three Seven had been barred in many foreign countries as it did not meet with their standards. By tackling these problems at design stage, a much larger market place was available to the new Seven.


Warner and his design team consisting of Alan Barrett, Dave Baldwin and Peter Lucas had a model made to ¼ scale which was the subject of a meeting with Colin Chapman. The design was approved in March 1969 and the team were given the go ahead to produce a full-size prototype. As cost was the uppermost consideration, there was never a question that the new body would be made of glassfibre rather than aluminium.

Factory Photo


The new body design consisted of two self-coloured glassfibre mouldings bonded together to form the outer skin and cockpit and scuttle including the rear wings. This unit was then bolted to the chassis via bobbins moulded into the glassfibre. A front hinged bonnet and a pair of re-styled clamshell front wings completed the bodywork. A Weathershield designed hood with sliding perspex side windows, albeit still hinged from the windscreen pillars a-la previous models, afforded much better weather protection.

Peter Lucas’ chassis design consisted of a simple spaceframe with two steel panels spot-welded to the engine bay and cockpit sides and a folded pressed steel cross-member over the centre of the car. To stiffen up the chassis, the glassfibre body also served to add to it’s torsional rigidity.


The new car’s all-Ford running gear remained mostly unchanged from that of the previous Series Three model. Ford’s 1300cc and 1600cc Kent ‘crossflow’ engines giving 76 and 84bhp respectively and the Lotus 1558cc twin-cam unit in Special Equipment 115bhp and Holbay tuned 125bhp forms. 4-speed gearbox from Ford’s 2000E and rear axle from the Escort Mexico completed the drive train.


Whilst using the stronger axle from the Ford Escort had reduced the problems associated with the Series Two’s Standard Companion item, there was still a problem. To overcome the notorious location problems of the previous A-frame arrangement, Peter Lucas used a pair of Watts linkages and a triangulated arm on the offside to deal with lateral location.

The front suspension now had proper double wishbones on each side. Previously the Series One, Two and Three models had top wishbones which utilised the anti-roll bar as the front leg. The new parts were similar to those on the Europa model being made from folded sheet rather than the tubular mild steel used before. Coilspring/damper units were fitted to all corners of the car as before.


The symmetrical dashboard was an integral part of the glassfibre body having three sunken panels, two being for instruments depending on whether the car was left hand or right hand drive. For the first time more comfortable contoured seats were fitted and even a hardtop was included as a factory optional extra!

Series IV Factory Announcement


Even by the design stage, Alan Barrett had never driven a Seven before, so he borrowed a metallic blue Series Three to go home in for the week-end. After the journey he never wanted to drive it again, he hated it that much, but by the time he had driven it back to the factory he was beginning to enjoy the experience. Obviously, he thought, it was an acquired taste! While designing the new car, Peter Lucas and Alan drove the old Series Three Seven as much as they could in order to understand the concept, it’s problems and how to improve them. To develop the chassis a test rig was made consisting of a chassis, running gear, windscreen, roll hoop and seatbelts to hold the occupants in. This was driven on the Hethel test track for as much as 200 miles a day. Whilst this was happening the body design was being finalised. Alan says that the team were left to get on with the design on their own and without interference from within Lotus or their dealer, Caterham Car Sales.


The prototype was produced in just seven months and the new car was launched a short time later in March 1970. With an excellent reception from the motoring press and effective marketing, production soon climbed to 15 cars per week. In order to be able to cope with Warner’s projected target of 2000 units a year, chassis production was given to two contractors; Arch Motors and Griston Engineering. Despite increasing the number of specialist main dealers from one to five (Caterham Cars Sales in Surrey, Harrop Motor Company in Cheshire, W. B. Sports Cars in Bristol, Sprinzels in London for personal export and Lotus Components at the factory near Norwich.) Warner’s sales figures were infact never to be achieved. However a £150 profit was maintained from of each car sold.

Price List from later brochure


However the small profit made on each Series IV was not enough to help the ailing ‘Lotus Racing’ (formally Lotus Components) arm of the Lotus Group. Competition, both in terms of purchase cost and track competitiveness, from builders such as Lola, Merlin, etc. meant that the market was very different to that a few years earlier. With heavy stock levels of unsold customer racing cars including some 54 three-year old Formula Fords, it was decided to cease building race cars for sale and wind-up the company. So after nearly 12 years, it was decided to move the Seven Series IV production to the Lotus Cars factory where the Elans were being built.


For some time Colin Chapman had believed that the future of Lotus as a manufacturer of road cars was to be found in the Ferrari/Porsche ‘supercar’ territory where profits were much higher. The Seven as a ‘kitcar’ did not fit into this new ‘supercar’ range and in factory built form, with purchase tax paid, it would be too expensive to be successfully marketed even as an ‘entry-level’ model. The decision for Lotus to stop production of the Seven was made as early as July 1971, but there was still enough stock of chassis frames for the model to be made until October 1972. In the event Lotus sold the Series IV Seven, for over three years, until well into 1973 by which time over 650 cars had been made.

Sources and further reading:

Lotus Seven by Jeremy Coulter (1986/1995)

Lotus Seven Preparation/Restoration/Maintenance by Tony Weale (1991)


bottom of page