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About Us

Grinnall Specialist Cars is a centre for innovation and radical sports car and motorcycle trike design, and home of the Scorpion-III, a BMW motorcycle powered 3-wheeler cycle car, and Scorpion-IV, a 4-wheeled big brother to the III powered by a turbo-charged Audi motor. Grinnall also specialise in making three wheeled motorcycle trikes currently based on the Triumph and BMW motorcycles. Please go to grinnall cars for further information on the Scorpion-III & Scorpion-IV.

Brief History

For three decades, Mark Grinnall has headed a team of talented designers, engineers and craftsmen who have dedicated themselves to providing top quality performance on wheels.

The company’s reputation was first made by its extensively reworked and refined conversions of the Triumph TR7 and TR8. By the early 90’s some 350 Grinnall TR8s had been constructed. In 2006 The Triumph Register acknowledged the Grinnall TR8 as a marque in its own right, and has compiled extensive history files on the vehicles.

New concept needed

In 1991, in search of a radical but affordable high performance concept, Mark Grinnall turned towards his passion for motorcycling, and his hand to an innovative three-wheeler, which unlike any of its illustrious ancestors would be high-tech, mid-engined and rear wheel driven. This was to be the first in a family of unique, niche-market sporting vehicles. The Scorpion-III made its debut in 1992 when it was featured in CAR magazine, an article written by a young Colin Goodwin. Interest in the S-III exploded in the mid 90’s, with the breathtaking featherweight being featured in dozens of magazines worldwide.

The S-III is still in production over 20 years after its launch. This is testimony of the design quality and pleasing aesthetic. Using an online Yahoo social forum a global network of owners share their interest in the cars and experiences, with organised events and tours in the UK, Europe and the US. Trouble shooting discussions develop and an archive of history has been compiled to assist owners with cars some of which are over 20 years old. Full factory back-up guarantees all parts and service are available for machines new and old.

The latest S-III model features the state-of-the-art BMW 1300cc 4-cylinder motor from the K1300S motorbike. With 185bhp, wider track, billet uprights, stiffened rear suspension and many other new features, this machine is lots of fun and very rapid. With 460bhp per tonne this little cycle car is guaranteed to upset Ferrari drivers, and can still return over 50 miles per gallon.

The next stage in the company history was to create a four wheeled version of the S-III. Development of the Scorpion IV began in June 1998. Research had confirmed the plan was the right one. At motor shows and demonstration days up and down the country at BMW Motorrad dealers – and via our website – a significant number of prospective customers, and some Scorpion III owners too, had been asking us to produce a four-wheeler. They wanted a little more interior room, and even more performance, mainly for the growing track day market. Since that time, several more vehicles destined for this niche have appeared – and some have disappeared. Possibly one of the most successful arrivals is Simon Saunders’ skeletal Ariel Atom.

Scorpion-III designer Steve Harper (SHADO) was again commissioned to style the S-IV to the same ‘form follows function’ design brief, and maintain a clear family relationship between the two.

Findings from the research and development of the highly-acclaimed Scorpion-III went into the building of the new Scorpion-IV chassis; a space-frame structure which is remarkably rigid, yet respectably light. The front suspension is a development of that which works so well on the Scorpion-III: Unequal length double wishbones in oval tubing with inboard coil springs over custom made gas dampers, with adjustable camber and castor. At the rear, long, super-stiff longitudinal links give superb handling and camber control without compromising the vehicle’s distinctive styling.

Exhaustive trials of possible power-trains included Rover K-series, Honda VTEC and Fiat 20v turbo – all fine products. Eventually however, we decided to use the incredible Audi/VW 20v turbo unit, which makes 225bhp in standard form and up to 500bhp after the tuning wizards have done their stuff. The slick Getrag 6-speed gearbox compliments this superb motor perfectly.

In 1999 work began on the first of our motorcycle derived moto-trikes – with a single front wheel. For us the obvious starting point for a great trike was the BMW R1200C – a machine that had the twin advantages of BMW’s tele-lever front suspension and shaft drive. Launched in 2000, this has been a constant seller for us.

To the Grinnall Trike collection was added the BMW R1200CL, the Montauk, the sportier R1150R, and on 2005 the Triumph Rocket 3 based trike – the R3T. This has been a wonderfully successful machine, and makes probably the best moto-trike on the planet. Continuing with Triumph a new moto-trike will soon be launched based on the fabulous Triumph Thunderbird 1600 and 1700. This new machine will herald the beginning of belt/chain driven trikes appearing in the future Grinnall range.


Opening Spring 2015 – New facility for sales and manufacturing

In 2013 we purchased a 2 acre former agricultural site on the outskirts of Stourport-on-Severn, Worcestershire (post code DY13 0TF). We would like to express our gratitude to WFDC planning department and committee members for granting planning permission for a new factory and retail showroom facility. Phase One has now commenced, and will open in Springh 2015.

The new site will allow the expansion of our moto-trike range, and finally enable full production of the Scorpion-IV. Re-organisation and production conformity will also allow us to comply with EU regulations and thus EU Certification of Conformity (COC), opening up huge sales potential within the EU. Neither production of the S-IV nor COC for the 3-wheeled vehicles was possible from the old site.

In 2015 we will be recruiting new staff in the assembly shop and sales. Interested motorbike engineers with an eye for detail and build quality are invited to register their interest via email with full CV.

Research And Development

R & D Partners

Recognising that we are a minnow in automotive production terms and that we cannot be expert in every field, we have worked (and will continue to work) in partnership with some of the best engineering and test facilities in the UK and Europe in order to optimise our innovative designs.

We are currently working with Steve Everitt, concept designer and builder of the Venom GT supercar as well as dozens of other notable automotive projects. Steve is currently involved in several developments for Grinnall which will be rolled out over the next few years.

New Products

They say in the automotive industry if you are not innovating you are going backwards. We are constantly developing and improving the entire Grinnall range. All the company’s original designs are highly evolved, but we listen to our customers and constantly strive to improve what we do.

Triumph Thunderbird Trike 1600cc and 1700cc

The Triumph Thunderbird is a recent 2-cylinder, belt driven 1600 or 1700cc motorcycle. Departure from the normal shaft drive has enabled us to develop a new and unique belt/chain drive system that increases the wheelbase and overall length to the same dimensions as the R3T. It shares the same fully independent rear suspension as our other trikes and has a unique optional mechanical reverse. A new set of billet yokes provides revised steering geometry to guarantee easy steering.

New styling, quite different to the R3T although designed by R3T stylist Steve Everitt, retains the original Thunderbird slash cut exhaust system with twin pipes exiting at low level. Retaining the original exhaust will ensure the machine will comply with the US CARB emissions for California and the E.U.

Enclosed in the body-work is a very large waterproof luggage compartment with a high level opening hatch/boot lid for easy access.

All mechanical development is completed and the chassis jigs are made. We are currently taking mounds off the clay buck. The finished machine will be available in March 2015. More updates on the development will appear here.


As ever, customer feedback is an important part of the development of all our vehicles and we welcome any constructive comments or suggestions that you have. Please email us with your ideas.


Grinnall Cars are keen to meet like-minded, enthusiastic people with relevant experience who would like to join the company. If you are someone who has a keen eye for detail, takes pride in their work, and needs a challenge in life, then please apply by emailing your CV to mark@grinnallcars.com

Current Vacancies

We are always on the lookout for keen potential employees for our Assembly Department. The work involves assembling new vehicles as well as picking kits, stock checking, servicing and repairs.

In 2015 following the move into new premises, we will be recruiting staff in assembly and sales. Interested motorbike engineers with an eye for detail and build quality are invited to register their interest via email with full CV. For more information please email your enquiry mark@grinnallcars.com

We may also have other opportunities coming up in welding, laminating and painting, so if you would like to join the Grinnall team please contact us.

In 2015 we will be recruiting new staff in the assembly shop and sales.

Visiting Us

Post Code (old premises up till March 2015) DY12 2YJ

Post Code (after April 2015 DY13 0TF)

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