The most important factor when buying spin bikes is the resistance and it’s really important to pick the right one so you don’t end up with too much maintenance and headaches. Unlike spin bike seats that can be replaces, resistance is a permanent mechanical part of the bike.
Resistance is the opposing force against the efforts you put on the bike. Basically, resistance is what makes the ride easy, moderate, and difficult. Easy to mimic flat street rides, moderate to mimic steep roads, and difficult to mim uphill rides.
Spin bike resistance plays an important role while cycling inside for exercise and entertainment purposes and if it’s not quiet or calibrated correctly, can ruin your cycling experience. Here are the three types of indoor cycling bike resistance systems:
Electronically adjustable magnetic resistance (the best)
Manually adjustable magnetic resistance (the second best)
Manually adjustable friction resistance (Inferior of all the three and to be avoided)
Electronic Magnetic Resistance Spin Bikes

The most comprehensive working mechanism Among the three type of resistance is involved in electronic magnetic resistance. Instead of using a knob to adjust ride intensity, this type of resistance uses buttons on the bike’s screen or handlebars. They are more convenient to use because you don’t have to let go off the handlebars to change resistance. You can change gears with the push of the button on the right and left handlebars and focus on the ride.
Another great thing about electronic magnetic resistance is that they are often built with smart technology that can automatically change intensity based on the programs that you are using to ride. For example, if you are on Zwift and going uphill, this type of resistance has the ability to automatically change resistance mimic uphill riding.
Just like manually adjustable magnetic, electronic magnetic smart spin bikes are very quiet and require little to no maintenance because there is no friction involved. There are a couple of magnets that come close to steel flywheel to add resistance and go far from the steel flywheel to reduce intensity. The only downside to electro magnetic resistance is that it requires to be plugged into wall socket to work. They don’t work on batteries and they are often not self-powered.
Manuel Magnetic Resistance Spin Bikes

As you can see from the name, magnets are involved in this type of resistance as well, except you need to change the resistance manually by turning a knob instead of pushing a button. This is the most common type of resistance used on spin bikes since 2020. Let’s talk about a traditional indoor cycling bike that has a flywheel on the front like the Stages SC3 or in the rear like Keiser M3i. Steel is the metal used to make a flywheel due to its brilliant magnetic conductance ability. Resistance is produced by the magnets placed on the top or on either side of the flywheel.
By manually tightening the resistance knob clockwise, you increase the intensity of the bike and the more tighten the knob, the hard it gets to pedal. Basically when you tighten the knob clockwise, the magnets get closer to the steel flywheel and they create a magnetic field. The magnets don’t touch the flywheel even at maximum resistance, they stay about 10mm far from the steel flywheel. Therefore, there is no touch, friction, noise, or part damages.
Have you ever heard in a physics lecture room that opposite poles attract each other? Every magnet has two bars; one is the south pole, and the other is the north pole, and these opposite poles attract each other when placed closer. In your standard indoor cycling bike, the flywheel works as a conductor between two magnets with opposite poles and generates plenty of opposing force to halt the spinning motion of the wheel. The only downside to this resistance type is that it doesn’t change automatically to mimic uphill and downhill when you are using indoor cycling applications such as Zwift or Peloton.
Manual Friction Resistance Spin Bikes

As the name suggests, this type of resistance includes friction which ultimately means there will be xtra noise and extra maintenance. In this type of resistance, opposition force is applied with the help of felt pads made or wool or cotton to increase or decrease the ride intensity.
These spin bikes either have cotton/wool pads on the upper side of the wheel or these pads on both sides of the flywheel similar to your old road bike brakes. When you add resistance by turning the knob clockwise, these pads touch and compress against the flywheel to increase resistance. The friction resistance phenomenon is common in most road bikes (for braking) and for old indoor bikes (for adding resistance/gear).
To be completely honest, I hate friction resistance system and I think you should try to avoid it at all costs because they are not as smooth as magnetic resistance spin bikes and they wear out after a while. Not to mention they start making annoying noise after a while especially if humidity or sweat reach them. The only good thing that I can think about friction resistance is the unlimited resistance that it offers. You have 100% control over the resistance intensity while in magnetic resistance, you get a preset minimum and maximum resistance.
What is the difference between magnetic and friction spin bikes?

To produce resistance, friction resistance pads come in direct contact with the bike’s flywheel which creates extra noise and cause the pads to wear out. With magnetic resistance it is the opposite, the magnets don’t touch the bike’s flywheel therefore, there is no noise and no worn out parts. It is impossible to detect even a little sound in magnetic resistance. Cotton and wool pads used in friction resistance system wear out after some time, so new pads are required from time to time to maintain the resistance level.
Magnetic spin bikes are more Costly or friction bikes?

To buy, magnetic spin bikes are a little more expensive but to maintain, friction spin bikes are more expensive. It’s because magnetic resistance indoor bikes doesn’t require maintenance or brake pads every year while friction resistance indoor bikes need new brake pads every couple of years. So, indoor bikes with friction resistance are less costly at first but gets more expensive down the road compared to magnetic bikes. Indoor bikes with magnetic resistance are strongly recommended. Friction resistance lags behind magnetic resistance because it needs regular maintenance. Worn-out-brake pads should be replaced after some time. On the contrary, a magnetic resistance bike is silent, easy to use even for beginners and requires less maintenance than other indoor bikes.
Magnetic or Friction Resistance is Better for Spin Bike?

With no doubt, magnetic resistance is the best choice for spin bikes. Friction resistance spin bikes come with annoying noise, additional maintenance, and more cost down the road to change the brake pads. As for manual-magnetic and electro-magnetic, they both are tough contenders to attain the first spot, and each one has its advantages and disadvantages. It is hard to differentiate between the rate of resistance produced by the magnetic systems.
Is spin bike resistance really important for indoor cycling?

Yes, very important. Spin bike resistance affect with noise, smoothness of the ride, and maintenance. I highly recommend magnetic resistance spin bikes as they are low-maintenance, make less noise, and are the smoothest of all. Having a thorough knowledge of different resistance types will come in handy.
How does magnetic resistance work on indoor cycling bikes?

When magnets get closer to provide resistance, the flywheel slows down and pedalling becomes harder. On the contrary, when magnets move away from the flywheel, it becomes easier to pedal indoor bike. Generally speaking, the closer the magnets to spin bike’s flywheel, the more resistance you would feel and the further the magnets, the harder it gets.
Conclusion
When looking for an indoor bike, having a detailed and accurate spin bike buying guide as a reference is a great start. As mentioned in my buying guide article, considering spin bike resistance should be priority, but often it is hard to decide the best. And that is precisely why I created this article. The selection of an exercise bike with suitable resistance depends on your needs. If you want smart automatic resistance change, choose an exercise bike that has electronic resistance. But if you want something that doesn’t require wall-socket plugin and you don’t care about automatic resistance change, then buy a manually adjustable magnetic resistance spin bike. If you want 100% control over the intensity of your spin bike’s resistance and you don’t care about extra noise and maintenance, then consider a spin bike with friction resistance. After making the final decision about which spin bike fits you bet, also remember that you are going to need proper indoor cycling clothing for a comfortable ride.