Magnum SD/XL Overview
Comfort & Lumbar Support
One of the secrets of the Magnum’s superior ride is the seat. While it may not look fancy, one ride is all you need to experience GreenSpeed comfort. Firstly, the seat was designed by a chiropractor, so that it has both proper lumbar and shoulder support. Then the seat mesh is laced to the frame by shock cord, so not only does the seat conform to your back, it also provides “virtual suspension” to insulate you from road shock. People are like car engines in that they are only about 33% efficient, thus if you are putting out about 100 watts in power, your body is radiating 200 watts of heat which has to be dissipated. Thus, the seat is made of an open mesh outdoor furniture material, to provide ventilation and cooling to the back.
To further enhance the ride, the Magnum uses the 2 inch wide Schwalbe Big Apple balloon tires. These tyres are designed to be run at any pressure from 35 to 70 psi on an ordinary bike. However, as the wheel loading is much less on GreenSpeed trikes, due to the even weight distribution, these tyres may be safely run as low as 20 psi, to give soft ride without much increase in rolling resistance. And while most aluminium bikes have a harsh ride, the Magnum prototypes were made in Cro Mo steel, and then every frame tube was translated by engineers to give the same stiffness in aluminium. Thus the 7005 aluminium Magnum frame has exactly the same ride stiffness the original Cro Mo prototype, one of which was tested in the Himalayas. Then the wider seat of the XL further enhances the comfort brought about by the careful design of the seat, tires, and frame.