Why the Hillman Imp became the first English rear-engined car
06/30/2012
When the Rootes Group presented the Hillman Imp in May 1963, the world was amazed. Not only had the developers designed a neat little car, the engine was in an unusual place for a British car, especially as the Mini had just demonstrated four years earlier that a modern car had the engine (and drive) at the front. In fact, the Imp was the first British mass-produced rear-engined car.
But the Rootes Group engineers had good reasons for choosing the rear engine, as P. G. Ware, chief technician of the Rootes Group and director of Humber Ltd. explained. The rear engine had a number of advantages, he wrote in his "Engineering Appraisal" in 1963:
- Almost ideal weight distribution, which was not dependent on the vehicle's state of charge
- Good traction even on slippery or sloping roads, good uphill capability because the drive is ideally loaded
- Better distribution of braking force to the front and rear wheels and more even tire wear than a front-wheel drive vehicle
- Better aerodynamics thanks to sleeker lines and the absence of a radiator element at the front, proven by the Imp's low fuel consumption
- Improved maneuverability, light and precise steering due to the elimination of weight on the front wheels
- No unpleasant influences on the steering wheel when accelerating
- Less noise for the passengers sitting in the front, i.e. the seats that are most frequently occupied
- Large distance between fuel tank (front) and exhaust (rear) and therefore less risk of fire
What P. G. Ware did not mention was that the decision to house the engine and drive in one place was made early on because they did not want to allow a gimbal tunnel and the associated space restrictions. This criterion was of course also fulfilled by the Mini, against which Rootes positioned the Hillman Imp.
Well, as we know today, the front engine with front-wheel drive prevailed despite the aforementioned advantages of the Imp configuration and not the rear engine, even though Porsche and Smart are still loyal to it today.
If you would like to find out more about the technical background of the Hillman Imp through the eyes of the Rootes engineers, you can find the five-page "Engineering Appraisal" of the Imp in the Zwischengas archive.
And of course there is a detailed article about the Hillman Imp.
