The Deal With The Flywheel: Why An Exercise Bike’s Flywheel Weight is Important

row of exercise bike flywheels
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If you’ve ever used or bought an indoor exercise bike, you likely know that the flywheel is one of the most important factors that separates decent, budget exercise bikes from more premium ones.

But what exactly is a flywheel? What role does it play in an exercise bike and should you be bothered about how heavy it is?

In this article, we’ll break down exactly what a flywheel is and why it’s so important when considering an indoor exercise bike.

What is the Flywheel on a Spin Bike?

A flywheel is simply a large disc placed at either the front (below the handles) or at the back (below the seat). It’s connected to the pedals via a belt or chain, and so it spins when you turn the pedals.

While some bikes have a very small flywheel, spin bikes, especially the best models, tend to have a prominent one. This is because the main function of a flywheel is to generate resistance while pedaling so that you can have a more challenging workout and burn more calories in the process. The more resistance you apply to the flywheel (i.e., make it harder for the flywheel to spin), the more effort you have to put into pedaling.

So, you’ll often see the weight being mentioned whenever flywheels are discussed. The heavier the weight, the more resistance it can generate (generally speaking). Besides resistance, the weight of a flywheel also determines how smooth the pedaling action of a bike will be.

When you cycle on an indoor bike, your pedaling action generates momentum in the spin of the flywheel. If your flywheel is heavy, this momentum will feel relatively smooth and unimpeded, and there won’t be any jerking when you increase or decrease your cadence.

Interestingly, some manufacturers have managed to achieve this feat even with lighter flywheels, which have their own advantages and will be discussed later in the article.

Flywheel weights can range from anywhere between 10lbs, all the way up to 50-60lbs for the very best exercise bikes on the market. Premium bikes generally have a flywheel that weighs around 40lbs, while budget bikes hover around the 10-20lbs range.

One thing regarding flywheel weights you should be aware of is something called a ‘perimeter-weighted’ flywheel. This simply means that the weight of a flywheel is concentrated at the peripheries rather than the center.

Some manufacturers will emphasize this aspect of a flywheel’s design while others don’t, which might make it seem like a special feature when in fact the vast majority of flywheels are perimeter-weighted.

The Different Types of Flywheels

We now know that flywheels primarily generate resistance for spin bikes. But how do they do this? There are primarily two types of resistance systems with their own mechanism for this: magnetic resistance systems and tension-based resistance systems.

As the name suggests, magnetic resistance systems utilize magnets placed on either side of the flywheel. Increasing the resistance brings these magnets closer to each other, making their magnetic forces collide with the metallic flywheel, thereby generating resistance.

The alternative, tension-based resistance systems, utilize pads that are in contact with the flywheel to generate resistance. This primarily exploits the friction generated from the obstruction created by the pad for the flywheel.

The problem with tension-based systems is that the pads eventually wear out and need to be replaced. They also make more noise and usually provide a less smooth ride compared to magnetic-based systems.

However, tension-based systems are cheaper. If you’re on a tight budget and are not necessarily intending on using this exercise bike for the long term, investing in a cheap bike with tension-based resistance is a good way to dip your toes into indoor cycling.

Heavy vs Light Flywheels

On the question of whether one should pick a tension-based mechanism or a magnetic one, we recommend going magnetic. They do cost more, but also provide a superior experience and require less maintenance over time.

Things get a bit more complicated when considering a heavy or light flywheel.

Both have their own advantages to take into consideration.

Heavy flywheels have a distinct advantage in that they provide a cycling experience more similar to the one you get while riding an outdoor bike.

Bikes with heavier flywheels take more effort to get started and build momentum, as well as providing higher resistance settings. These resistance factors make riding a bike with a heavy flywheel more reflective of riding outdoors on a road.

While it may take more effort for you to keep up the momentum (which can be avoided by keeping the resistance low), heavier flywheels also make the pedaling feel incredibly smooth.

So, why would anyone want a lighter flywheel?

Practical concerns are one part of the reason. Bikes with heavier flywheels are more expensive. They are also obviously heavier and make it inconvenient to move your bike around.

If you have limited space, you might want to store your bike away when it’s not being used but having a bike with a heavy flywheel will make this more difficult to do.

Moreover, some people may be turned off by the effort required to build momentum with a heavier flywheel. Not everyone wants the outdoor experience at home, and heavy flywheels do require more effort to get going.

With some models, you might not experience any tradeoff in the smoothness of the pedaling motion even if you choose one with a lighter flywheel. Having a heavy flywheel is only one of two ways you can make the pedaling action of a bike smooth, the other is to simply make the flywheel rotate faster with less force.

Manufacturers like Keiser have mastered the art of creating such flywheels, but this type is still overall rare.

What’s the Best Flywheel Weight for My Next Indoor Bike?

Now that we’ve laid out the pros and cons of having either a light or heavy flywheel, it’s easy to make an informed decision about which one is more suitable for you.

If budget is not an issue for you and you want an indoor exercise bike that mimics an outdoor one, a bike with a heavy flywheel is a no-brainer. This is also true if your fitness goal is to lose weight and you want to burn more calories because a bike with a heavy flywheel will provide more of a challenge to you.

On the other hand, if you’re only looking to casually exercise for secondary benefits such as maintaining your heart health and do not need too much of a challenge, a lighter flywheel might make more sense.

This will also save you space because many bikes with light flywheels are foldable and can be stored away when not in use. A bike with a light flywheel will also cost significantly less, meaning you’ll potentially save several hundred dollars.

What’s the Flywheel Weight on a Peloton Bike?

The flywheel weight on a Peloton bike is 38 pounds, which comfortably places it in the category of heavy flywheels. While this isn’t as high as several other premium bikes, it’s more than sufficient for the average user looking to lose weight.

Summing Up Flywheels

If you’ve made it this far, you should know everything you need in order to select an appropriate flywheel for your next indoor bike.

There are primarily two considerations to keep in mind: the type of resistance mechanism your flywheel uses and the weight of your flywheel. Both of these play an important role in how smooth pedaling on the bike feels, as well as how many calories you can burn during your workouts.

While there is a great range of choices in terms of the flywheel dynamics available, generally, if space and money aren’t an issue, purchasing a bike with magnetic resistance and a heavier flywheel is advisable.


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