ASUNA 4100 Indoor Cycling Bike

ASUNA 4100 Exercise Bike

ASUNA 4100 Indoor Cycling Bike Review

This mid-range exercise bike from Sunny Health Products manages to pack in a number of high-end features for an affordable price.   The ASUNA 4100 also looks and feels great, with a welcome splash of vibrant color on the flywheel and bike frame!

Commercial-grade build and quality, combined with a heavy duty flywheel, the ASUNA 4100 bike is an ideal product for those looking for something that will last years.

Cycling is a perfect, safe, low-impact option for exercise.  Not only does cycling help you to build up the strength in your legs, but it works the heart and lungs providing cardiovascular benefits.    The ASUNA 4100 bike can be used to do a variety of cycling workouts, but it is probably best used for spinning or interval type training.

Our full ASUNA 4100 Bike review

The ASUNA 4100 was released for sale in 2016.  SUNNY Health and and Fitness are one of the fastest growing companies in the fitness sector and have developed an excellent reputation for creating ‘gym quality’ exercise equipment which is also suitable for home use.
The 4100 bike is part of the ASUNA range developed by SUNNY.  The ASUNA range consists of high quality exercise products similar in build and structure to those you would find in a commercial gym.

The ASUNA 4100 bike is the TOP-SELLER in this range, providing a quality product at a reasonable cost.  Other bikes in this range include the ASUNA 5150 Magnetic Bike  and the ASUNA 5100 Magnetic Bike .  These bikes have slightly higher specifications than the ASUNA 4100, and are therefore also slightly more expensive to purchase.

This review will focus on the features of the ASUNA 4100 Bike including:

  • Heavy duty steel frame and great build quality and sturdiness
  • 40 lb chrome flywheel
  • Chain drive mechanism for smooth/quiet workouts
  • Fully adjustable seat and handlebars
  • Maximum user weight of 285 lbs
  • Build in transportation wheels
  • ‘Micro’ adjustable resistance system

Click here to see latest price on Amazon >>>

Frame and Build

ASUNA 4100 Exercise Bike

The frame is made from heavy duty steel, built to withstand years of cycling!   The bike is therefore heavy and sturdy.  This is a major benefit as it means the bike should not move or slip during a workout.   It comes with handy transportation wheels that should enable the bike to be moved freely.  Some users have reported that these small transportation wheels can occasionally get ‘stuck’ on thick carpets.

This frame accommodates most cyclists and a range of heights and builds.  The ASUNA 5150 bike is of higher specification than this model and provides the most generous allowances for taller/shorter individuals and accommodating heavier users.

This ASUNA 4100 has a user capacity of up to 285 lbs.

The lowest seat setting is 29″ (saddle to pedal) and the highest seat setting is 37″ (saddle to pedal).  This means the bike is probably comfortable for those between 5’2″ and 6’3″


ASUNA 4100 Exercise BikeThis ASUNA 4100 exercise bike comes with a 40lb chrome flywheel.   This is a heavy duty flywheel that will stand the test of time.   The heavier the flywheel, the smoother the ride and 40lbs is one of the heavier flywheels available.   Sunny Health and Fitness have also made the flywheel a funky vibrant color (which is a welcome change from the boring greys and blacks of most exercise bikes)! 

Cycling on the ASUNA 4100 bike should replicate the feeling of cycling outdoors.   With no clunking or jerking, the flywheel and chain drive mechanism are designed to facilitate  a smooth and natural ride.

Resistance can be altered by turning the knob handily located below the handlebars.   Resistance can be micro-adjusted in this way.  The ASUNA 4100 is therefore suitable for all exercisers as the workout can be as easy or as hard as you prefer.  Common to most spin bikes, there is no marker on the knob so it can be difficult to replicate exactly the same resistance with each workout.  We would recommend using a heart rate/calorie burn monitor if you would like to have a ‘measure’ of how hard your exercise sessions are.

The resistance mechanism uses a small felt pad against the flywheel to increase or decrease drag.   This felt pad is fairly sturdy, but will probably need to be replaced as some point (can be ordered direct from the supplier).


ASUNA 4100 exercise bike

The pedals provided with the ASUNA 4100 are reversible.   If wearing cleats is your preference, there are SPC clips on one side of the pedal.  If however, you prefer to wear regular trainers, an adjustable foot cage is supplied on the other side of the pedal.   These options both reduce the risk of slippage when cycling and help improve power output.



The ASUNA 4100 Exercise Bike comes with a fully adjustable seat which can be adjusted up and down but also forward and aft.  This allows most users to experience the most comfortable seating position throughout their workout.
The seat is slightly padded but several users have complained that is feels rock hard.  This can be easily overcome by covering the seat with a gel cover, such as this one from Schwinn:

The handlebars are padded and slip free allowing users grip comfortably in a variety of positions.   The handlebars are also adjustable up/down and forward/backwards so you can create the optimal placement based on individual preference and body measurements.  

There is also a conveniently placed water bottle holder located on the frame.


ASUNA 5150 Magnetic Bike
The ASUNA 4100 Exercise Bike comes pre-assembled with a shipping weight of 121 lbs. 

The main body of the bike (e.g. the frame, flywheel, resistance mechanism and belt) comes already assembled for your convenience.  All you need to do is attached the stabilizers, seat, pedals, handlebars and the water bottle holder.  Tools are also provided.  Assembling the bike should take around 15 – 30 minutes with minimal inconvenience.

The ASUNA 4100 Exercise Bike has convenient transportation wheels attached to the bike so it can simply be tilted and rolled into a suitable location.


What do others say about this bike?

“Extremely well build and easy enough for even me to assemble, but it is heavy”

“I like the built in transportation wheels, which allow you to move the heavy bike around easily. Roll it in front of your TV and then roll it back when you’re done with it”

“The nice thing about it also is that it’s not HUGE like some equipment. It is actually rather small, but very well constructed”

“The 40 pound flywheel provides a smooth and consistent resistance that is easily adjusted on the go with just the turn of a knob”


Sunny Health and Fitness provided a 90 day manufacturer’s warranty on this bike.

Do you need to know anything else? Here are the bike’s specifications:

  • Fully adjustable seat – Up,Down, Fore, Aft
  • Lowest seat setting: 29.5″ (Seat to Pedal)
  • Highest seat setting: 36″ (Seat to Pedal)
  • Fully adjustable Handlebar – Up,Down,Fore,Aft
  • Combination pedals – SPD clip and cage
  • Felt Brake Pad Tension – micro adjustable
  • Chain drive transmission
  • 40 Lbs chromed flywheel
  • Heavy duty steel frame structure
  • Assemble Dimensions: 41.3″ x 25.5″ x 51.2″
  • Maximum user weight: 285 Lbs

Alternatives to the Asuna 4100 Bike:

The ASUNA 5100 Magnetic Bike and the ASUNA 5150 Magnetic Bike are new on the market for 2017.

Both have slightly higher specifications that the ASUNA 4100.  The ASUNA 5150 is a ‘top-of-the-range’ bike with considerable adjustablity and caters for cyclists of all shapes and sizes.  Both these bikes use magnetic resistance technology (instead of the felt brake pad tension).   Magnetic resistance is believed to be a smoother and more reliable option.

Here are some other alternatives:

Product nameRating Price
ASUNA 4100 Commercial Indoor Cycling Bike, Gray ASUNA 4100 Commercial Indoor Cycling Bike, Gray
ASUNA 5100 Magnetic Belt Drive Commercial Indoor Cycling Bike Silver ASUNA 5100 Indoor Cycling Bike
ASUNA 5150 Magnetic Turbo Commercial Indoor Cycling Bike ASUNA 5150 Magnetic Turbo Commercial Indoor Cycling Bike
BodyCraft SPX Club Indoor Cycling Bike BodyCraft SPX Club Indoor Cycling Bike
Diamondback Fitness 510Ic Adjustable Indoor Cycle with Electronic Display and Quiet Magnetic Flywheel Diamondback Fitness 510Ic Indoor Cycle


Review Summary of the ASUNA 4100 Magnetic Bike

ASUNA 5150 Magnetic Bike

The ASUNA 4100 Exercise Bike is a mid-range bike, that has a solid build that one might expect from a more expensive bike.   It comes at an affordable price, yet has the look and feel of a gym-quality exercise product.

Click here to see latest price on Amazon >>>


Due to the shipping weight of the bike (around 121lbs), this bike could be be difficult to move into upper floors and apartments.   Convenient transportation wheels are provided however, so once it has been assembled, moving the bike from one place to another shouldn’t be a problem.

There is no in-built console with this ASUNA bike 4100.  Many users like to monitor their efforts when using an exercise bike – such as time, distance and calories burned.    We would recommend the purchase of an activity monitor such as a Fitbit that will monitor individual activity levels throughout the day including energy expended when exercising:

Some users have reported that the handlebar position is no the most comfortable, but this is down to individual preference.

In summary, the ASUNA 4100 Bike is ideal for new or regular exercisers looking for a solid product, with which they can do a basic but effective workout.  It comes at an affordable price tag and users should be able to get a number of years use out of this product.

ASUNA 4100 Commercial Indoor Cycling Bike, Gray Review Summary:

  • The 40 lbs. chrome flywheel delivers. stability and riding momentum
  • Fully adjustable seat and handlebar for maximum comfort
  • Micro tension knob system allows for various resistance levels
  • Chain drive mechanism for smooth and quiet workouts
  • Heavy duty steel frame with built in transportation wheels for easy portability; 285 lbs. user weight capacity

ASUNA 4100 Exercise Bike