What Exactly is a Flywheel?

May 01, 2019

What Exactly is a Flywheel?

The most prominent feature on most indoor spin bikes is bar far the flywheel, that big round disc that spins around underneath the bike at the back or the front, and which is connected to the pedals by way of a belt or chain drive. But what exactly does the flywheel do, and why is it so important?

When Johnny Goldberg (Johnny G) invented the concept of the flywheel back in the mid-1980’s, his goal was specifically to simulate a real world outdoor cycling experience. When you begin pedaling on any outdoor bike, you need to push hard to get it going. Your bodyweight is providing the resistance you push against, while at the same time, it gives the bike its momentum, moving the bike forward even when you stop pedaling.  This is the experience that a heavy flywheel creates for the rider on an indoor cycle. The heavier the flywheel is, the harder it is to get turning and once you have it turning the longer it will take to slow down because of the momentum that has built up, even after you’ve stop applying force to the pedals, simulating the act of coasting on the road and not have the wheels come to a quick stop. 

As a result, the weight of the flywheel is largely what determines the fluidity and comfort of indoor cycling experience. A heavier flywheel stores more energy which then smooths out the cycling experience for a consistent cadence (the speed at which your legs spin as they pedal) while also smoothing out any defects caused by the friction on the resistance pads not grabbing the wheel evenly due to poor adjustment or wear.

On the other hand, a light flywheel requires constantly adjusting your pedaling speed. For more casual cyclists, a lighter flywheel may be preferable, but for more intensive cycling, since there is no weight to keep the pedals turning, the pedaling becomes more of an up and down motion which can put pressure on your joints and make you more susceptible to injury. Flywheels range in weight from around 30 pounds to 50 pounds depending on the manufacturer’s specification, however the weight that the flywheel begins to be heavy enough that the cycling motion starts to become more fluid and natural is around 30 lbs. Keep I mind also that a heavier flywheel means the overall weight of the stationary bike is naturally heavier, which means it’s less the portable, while the price tag is usually higher as well.

Ultimately, the flywheel weight that is best for you will depend on your overall fitness goals.


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