Understanding the Physics Behind Steering Your Trike
Simply put, the center of mass is the point at which the weight of an object, in this case our trike, is equally distributed in all directions. This point is variable. Even when we are stationary, the center of mass depends not only on the trike’s weight distribution as it was designed, but also by where we sit, if we have a corider, what’s in our saddlebags and trunks, and if we are pulling a trailer, etc.
Surrounding the center of mass on our trikes is what is referred to as the triangle of stability. This is the light green area illustrated in diagrams A, B and C. It extends from the center of the contact patch(es) of the front tire(s), to the contact patch(es) of the rear tire(s). These are the points “where the rubber meets the road.”
Unlike our two-wheel brethren who counter steer and lean as they enter a turn or curve, we enter them by pushing and pulling on our handlebars which leaves us relatively flat to the road surface. Doing so results in centrifugal force pushing everything – us, our co-rider and the weight of the trike toward the outside. (See Diagram B on next page.) The more acute the curve or turn, and/ or the greater our speed, the more the centrifugal force and resulting weight shift will occur. Too much weight shift toward the outside of the trike can cause the inside wheel to lose traction – or worse, a crash.
Enter the triangle of stability.
So, how can we exercise control over this weight shift? By moving our weight (See Diagram C), we shift some of the center of mass back toward the center of the triangle of stability. For riders, this can mean shifting our butt toward the inside of the turn (known as counter-weighting) and to the rear. The amount of movement needed will vary according to what is required to counteract the outward force being exerted by the curve or turn. In most instances, I prefer to just lean my body, from the hips up, while tilting my head enough to keep my eyes level with the horizon. For the co-rider – put your hands on your thighs (or hand grips if you have them) and push against the backrest. All of these actions help change the center of mass in our favor (and are ones that you will become more familiar with at our Practice Field Days).
Is there a difference if our trike has two wheels in front and one in the rear? Essentially no. The center of mass may be slightly more forward on a trike with two wheels in the front, but you still counteract the centrifugal force in the way described in the previous paragraph. (Note: The instructions in the Can-Am Spyder Owners Manual recommend leaning slightly forward rather than leaning backward.)
A final note – and it’s an important one – the better you correctly judge your entry speed for curves and turns, the fewer centrifugal forces will be working against you and your trike, and there will be less need for you to compensate by counter-weighting. This is a learned skill for all of us – so practice, practice, practice. (This is not-too-subtle hint for you to attend Parking Lot Practices in your area. They are a great opportunity to learn and relearn our perishable skills!
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