Brake-Based Systems This is the most primitive mode of resistance available in the market, as it uses the same technology used in conventional bikes to stop or slow down. In the same way, it utilizes a controlled braking system to increase or decrease the resistance.
There are several kinds of braking systems made specifically for this purpose, such as the hydraulic disk brake, the drum brake, the coaster brake, and so on. These braking systems apply friction to the wheel of the exercise bike to create resistance.
It is the most inexpensive bike on the market, but it cannot contend with the latest bikes as it uses obsolete technology.

Direct Contact Resistance The direct contact mechanism used to be the most popular choice for fitness fanatics. The level of resistance offered by it is truly unmatchable. It is based on the principle of friction and uses a brake pad to apply direct contact on the flywheel of the bike in varying quantities to get the desired intensity of resistance. The brake pads allow you to customize the resistance generated by the bike.
These bikes are preferred because they are capable of producing high levels of resistance, guaranteed to challenge even the most skilled riders. Moreover, they are highly affordable and even offer various levels of difficulties, from beginner to advanced, making them extremely adaptable.
However, there is a reason this bike used to be the best in the market. The reason is that it is the definition of high-maintenance. The friction of the brake pad on the flywheel causes mechanical wear and tear over prolonged usage. If you buy this bike, you will have to incur additional costs on top of the initial investment to fix the repeated damage. On top of all that, these bikes are extremely noisy and will disturb everyone around you.

Magnetic Resistance Magnetic resistance exercise bikes dominate the modern marketplace. They provide a solution to all the predicaments linked to the direct contact resistance bikes. These bikes create a powerful resistance with the help of the flywheel and two strong magnets.
The magnets are positioned on either side of the flywheel but are never allowed to make contact with it. As one rides the bike, the rotation of the flywheel disrupts the magnetic field. This attraction creates resistance which makes it more difficult to peddle. When a more elevated level of resistance is needed, a knob is turned to bring the magnets closer to the flywheel and vice versa.
These noiseless bikes are remarkably advantageous to own, as they require no maintenance. Since the magnets do not come in direct contact with the flywheel, there is no mechanical wear and tear which would require regular replacement. Moreover, it empowers the rider to customize the workout by allowing them to precisely adjust the level of resistance. This feature is absent in all other forms of resistance. And most importantly, these bikes replicate the unbeatable resistance offered by direct-contact bikes minus the imperfections. However, magnetic bikes are quite expensive and may not fall within everybody’s budget.

Fan /Air Based Resistance This genre of exercise bikes features a fan in place of the usual flywheel. The mechanism behind this style of resistance is pretty simple. When you increase your rate of peddling, the fan has to churn out a greater quantity of air which results in heightened resistance. But when you decrease your rate of peddling, the fan has to go through lesser volumes of air, which directly results in reduced resistance. This system of resistance is unique and offers many perks which the other three kinds don’t. Firstly, cool breeze from the fan makes its way towards you during your strenuous workout, cooling you down, almost instantly. Secondly, it requires very little to no maintenance. This is because it is composed of minimal moving parts. Thirdly, it is comparatively less noisy and accommodates smooth functioning, which allows you to workout with ease. The only major disadvantage is the cost involved in the investment as it requires an expert in the field to set it up due to its specialized nature. Another notable drawback is that since the only way to increase the resistance is by speeding up, some users might find it less beneficial due to its lack of customizable capacity.