Scorpion III

Sting your senses!

The Basics

The concept

Inspired by the original Morgan 3-wheeler, the Grinnall Scorpion-III looks forward rather than backwards. Featuring ultra-high performance motorcycle power from BMW Motorrad combined with a lightweight space frame chassis and sophisticated suspension clothed in a composite body, the S-III owes far more to today's race car technology than it does to its illustrious ancestor.




In 1992 automotive stylist Steve Harper (SHADO) was commissioned to pen an exciting new design adopting the 'form follows function' philosophy. Designed in-house, the space frame chassis and race-bred suspension have been continuously refined to guarantee the highest safety and performance standards consistent with the lowest possible weight.


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Drive Train and Chassis

The S-III was conceived and developed to use drive trains from BMW's range of 4-cylinder motorbikes. The latest – the K40 – produces an eye-watering 185bhp from just 1300cc. The vehicle weighs only 390Kgs (862lbs) which translates to over 460bhp/tonne. The earlier motors can still be fitted which produce between 100bhp to 135bhp.

Grinnall Cars are BMW 'partners' with an Original Equipment Manufacturer supply status. This special arrangement enables us to buy engines and parts directly from BMW.




Six speed transmission and wet multi-plate clutch are standard features, along with shaft drive. Early 1100 and 1200cc drive trains use a car type single plate dry clutch, and reverse is an option. Later motors are dry-sumped – which guarantees complete lubrication, improved cooling and no oil surge while cornering.




The Scorpion-III uses the standard BMW rear swinging arm suspension system. The current K40 version features ‘rising rate’ suspension which gives an ultra-smooth ride with spring and damper rates that rise on demand. Learn about rising rate.


Front suspension is by double wishbones with in-board gas dampers and anti-roll bar, featuring in-house designed CNC machined billet alloy uprights. This combination provides maximum feel, straight line stability and precise handling.


The Scorpion-III is fitted with a light alloy adjustable steering rack, and an in-house designed, adjustable, needle roller bearing steering column, thus ensuring the steering is light and precise with plenty of driver feedback.


Billet 2-pot calipers and large vented front discs ensure the brakes never fade, even on the most enthusiastic track days. Rear braking is standard BMW with adjustable front-rear pressure bias.


The K40 has digital engine management and CANBUS technology featuring momentary switching directional indicators, digital dashboard and proximity sensing ignition switching. However, this system needs to be complete when removed from the donor bike in order to operate. To make life easier, especially for the export markets, Grinnall have developed a stand alone engine management system that dispenses with the complex CANBUS system. Our plug-and-play system is simple to fit and it’s no longer necessary to hook up with the BMW computer system for engine installation. Both systems are keyless, and guarantee amazingly smooth torque, fantastic full power performance, and frugal fuel consumption. A Momo Racing detachable steering wheel is an added anti theft device.