Trike suspension Motorcycle based trike

Arguable, there are three basic suspension systems, which can be used on a motorcycle-based trike. Live axle. De-dion axle and Independent.

In this article, we will examine the pros and cons of each system in an attempt to determine which is the most suitable in the construction of a motorcycle based trike using conventional motorcycle telescopic fork steering.

We are deliberately omitting the commonest home build set up which is best described as, "rigid" or, "hard tail" as this does not represent a suspension configuration and is also technically not sanctioned by the construction and use regulations for a vehicle with more than two wheels.

We will begin with the configuration most common with professional motorcycle trike builders:

Independent suspension

This set up is to be found on most four wheeled vehicle having sporting aspirations and has the huge advantage of being able to deflect minor bumps and road imperfections without disturbing the camber castor angle of the deflecting wheel or the plane of the vehicle. This configuration is by far the optimum set up for use in a four-wheeled vehicle and probably explains its attraction to the trike scene.

Its main disadvantage when applied to a three-wheeled vehicle is inability to control body roll. With only three wheels, when one independent rear wheel is deflected, the vehicle leans in that direction causing the entire vehicle to roll the opposite way during cornering, requiring heavy anti roll bars or very stiff springing to address the problem. Axles donors are plentiful, Sierra and BMW being the commonest.

De-Dion axle

Possibly the ideal axle set up for a three-wheeled motorcycle.

This configuration has the advantage of no camber displacement on rebound, reducing the undesirable roll effect of the independent suspension set up without the use of heavy anti roll bars or stiff spring shock combinations. The De-Dion axle shares the benefits of the independent axle by having the differential unit static mounted in the frame while the wheel hubs move up and down using a trailing arm system connected by a rigid beam from hub to hub controlling the body roll.

Main disadvantage of this system is weight and cost, De-Dion axles are rare. Rover P6 axles spring to mind but are few and far between these days, however, it is possible to manufacture a De-Dion style axle from the common independent axle cars, for example: Sierra and BMW.

Live axle

As used in most 70's and 80's rear wheel drive cars, these axles were cheap to manufacture and very plentiful. Not so plentiful these days and scarcer still in final drive ratios suiting motorcycle trikes.

The humble Reliant and Ford Escort/Capri axles are the live axles of choice for most builders as they are available in high final drive ratios, suiting the majority of motorbikes.

Disadvantages of the live axle are constantly varying camber castor angle during pre-load and rebound affecting the plane of the vehicle leading to a shaking at the headstock. This is hugely offset however by the stability of the vehicle during cornering making high cornering speeds a real possibility whilst not compromising weight or ride comfort Designed sensibly, as in the popular Rhino trike range, a live axle set up can be the optimum arrangement for a motorcycle trike. Very important with a live axle trike is choice of front tyre and tyre pressure with a flat section wide front tyre running relatively low tyre pressure being the optimum choice.

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About the Author:
Nick Boyland is an engineer working in the manufacture of motorcycle-based trikes. Having twice worked as an engineering expert for TV's "Scrapheap Challenge" (Junkyard wars) Nick has written many articles and reviews on the subject of Motorcycle trike design http://www.rhino-trikes.co.uk
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