Adding mass above the axles on a motorcycle along the pole of the cg of the roll axis is only felt as tippier when the bike is on the stand or when yanking it backwards out of a parking space. Once you are up and rolling at speed, any added mass that is right behind the rider and laying along the area of the passenger seat is not felt in the roll movements of the bike because it is actually moving less than if it were lower. As the bike leans the wheels away to self correct in cross winds for example. I have come to determine that the it is best to have the roll cg much higher, and focused along the pole, than the center of pressure when viewed from the side in order to get the best side wind performance. You will notice that modern race bikes have evolved to move the rider and mechanicals slightly higher while the bodywork at the bottom of the bike almost scrapes the ground when fully compressed to keep the side CoP low. Raising the mass higher on a race bike is also done to allow less required lean angle for any given cornering force. The tires stay more upright.
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My CBR250R rides through highway winds just as well with 60 pounds of gear on my rack.
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The real culprit to avoid is letting the weight get to far to the rear of the bike where it begins to unweight the front tire and also causes the yaw movements of the tail to become high polar and wag.
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Notice how much effort was put into making the bodywork almost drag the ground and how high the seat is on this brand new Moto3 bike.
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