When you're thinking about investing in new motorcycle, it's easy to think the engine is the most important consideration. The engine makes the bike fast and fun, but a ride without suspension is a pretty unpleasant experience. Suspension affects how the bike looks, rides, and feels, so it's hard to overstate how important it is to the riding experience.
The quality of a bike's suspension dictates how it will perform on the road. Because a motorcycle only has two points of contact with the ground (as opposed to the four that a car has) suspension is doubly important. In the back, suspension helps to ensure that the rear tire is always on the ground so that it can have traction for acceleration and braking. In front, the same is true, but it affects steering instead of acceleration.
The best suspension systems can be adjusted to the rider's needs. Motorcycle suspensions are always under tension, and the amount of tension is known as the "preload." Suspension that's too loose can reduce traction, but suspension that's too tight isn't very comfortable to ride. Finding this balance is heavily dependent on the rider's size and weight because heavier riders will need tighter suspension. A person may also change the suspension tension based on the type of riding they enjoy. A sport bike meant for track riding or taking tight corners in cities might benefit from a stiffer suspension, while a touring bike made for taking long trips might want a little more give to make long trips more comfortable.
Parts of Suspension
The most common type of front suspension for motorcycles is the telescopic fork design, which is generally comprised of two main parts: springs, and dampers. The springs offer the actual support of the bike, and are always under tension. The dampers essentially dampen the spring function to reduce the amount of bounce in the springs. Dampers are filled with oil that must pass through an orifice. Without the dampers, the bike would continue to bounce up and down after hitting a bump. There will also often be bumpers so that if the rider bottoms out the suspension, there will be some cushion. One somewhat common other design for suspension is the inverted fork design, which function in essentially the same way, but the forks are upside down so that the dampers are on the bottom. It's said that this can improve handling.
For rear suspension, most motorcycles use shock absorbers like you might find in a car. Whereas the forks in front feature springs that are inside the forks, the rear suspension uses a coil-over spring design in which the spring is outside the shock. These shocks may be adjusted for preload, and sometimes feature an external reservoir for oil.
Suspension on a Harley-Davidson®
Finding the right suspension and getting it dialed in to your personal specifications may take some time, but Harley-Davidson® is always at work to develop new systems that work for more riders. Harley-Davidson® also offers upgraded suspension systems for their bikes to bring the handling and comfort to the next level. This can only be fully experienced in person on a bike that's been adjusted to your needs.