A lady exercises with the Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike

Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike Review

The Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike and the Synergy SF-B1879 version looks pretty much the same but they aren’t technically.

The former has upgraded features that include support for higher user weight capacity, possesses a mid-range console, dual-sided pedals, and more.  

The differences between these two models are put in better perspective in the comparison table below.  

Click right here to have a peek at the Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike on Amazon.  

Table of Comparison

Synergy Pro SF-B1851Synergy SF-B1879
MAX. USER WEIGHT CAPACITY300 lbs./136 kg275 lbs./125 kg
FLYWHEEL40 lbs./18 kg30 lbs./14 kg
PEDALSDual-sided (clip-in & toe cages)Toe cages

The Frame and Construction 

Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike

The Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike is mostly made of solid steel that is coated with anti-corrosion paint (seat/handlebar posts are chrome-plated), with exception of the drive train that is made of ABS.  

Hence, it is durable and sturdy enough to last longer and support a maximum user weight capacity of 300 lbs./136 kg.  

The bike’s adjustable steel base and its assembled weight of 111.3 lbs./50.4 kg ensure and guarantee stable workout performance.

There are transport wheels at the front base for an easy relocation process. 

The overall assembled dimensions are 49’’ long by 22’’ wide by 46.5’’ high. Consequently, the bike requires a workout area with perimeters of 4’1’’ length by 1’9’’ width, plus additional extra clearance of 2’ around it for safety and conduciveness.  

The Seat of the Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike 

This bike has the same type of seat as the one on the SF-B1879. It is comfortable than the average indoor spin bike saddle.  

It is cushioned with layers of foam and graced with a groove in the middle to dispel the heat and maximize comfort during a prolonged workout.  

The dimensions are 10.5’’ long by 7’’ wide by 1.5’’ thick.  

That said, a gel seat cover can be used to further improve its comfort level. Due to its standard connection mechanism with a collar, it is entirely possible to replace it with another saddle of your choice.  

The seat is vertically (up/down) and horizontally (fore/aft) adjustable. This enables you to position the seat for a perfect fit, and it is suitable for users whose inseams are between 29’’-39.5’’.  

The Handlebar 

The multi-grip ergonomic handlebar is 2-way adjustable (vertically only). It supports the seat’s adjustability so that users can find a seamless workout position.  

It is well coated with soft rubber foam material for comfortable and secure grips that prevent blisters and slippage.  

Due to its multiple hand grips, one can exercise in a variety of riding positions.  

Lastly, there are HR sensors on the handlebar that read and transmit the heart rate data to the monitor when grasped during a workout.  

The Pedals 

The pedal of the  Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike

The Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike has dual-sided pedals. This means, one side of each pedal is toe caged, while the flip side is SPD.

Therefore, you should be able to use either a pair of standard gym shoes or special spin shoes. 

The solid crank-arms and the crankset the pedals are attached to hold up during a stand-up pedaling.  

The Drive  

This indoor spin bike has a belt drive system that comprises a heavy-duty anti-stretch belt, a pulley, crank-arms, a crankset, and a 40 lbs./18 kg high inertia perimeter weighted flywheel.  

Its operation is smooth and quiet, hence, it is preferred by most spin bike enthusiasts over a chain drive system.  

You can exercise with undivided attention to achieve your fitness goals without being bothered that someone might be disturbed by your activity. You may also decide to watch a TV show/movie or listen to music while working out without noise interference from the bike.  

There is no obligation to pre/post-lubricate or adjust any part. In other words, the drive system is also maintenance-free.  

Since it is not possible to coast as one could on a road bicycle, you must apply the emergency brake for safety reasons by pushing the tension knob down whenever you wish to quickly exit the bike.   

That said, the fixed drive makes it possible for users to pedal in reverse.

The Resistance 

The Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike is equipped with a manual magnetic resistance system. This is a popular type of resistance system that doesn’t alter the smoothness and quietness of the bike’s operation.  

It works in sync with the heavy flywheel making the bike’s operation smoother, solid, and quieter.  

The resistance levels are unlimited, and not predefined. So, you will have to turn the tension knob clockwise or counterclockwise to increase or decrease the workout challenge to your desired level.  

Since the resistance is generated when the magnetic brake pad emits magnetic fields on the top surface of the flywheel without actual contact, no part wears out, and consequently, no part needs to be replaced in the long run.  

The Console 

The console of the  Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike

This model has a mid-range console that features an LCD monitor that displays multiple workout data simultaneously.  

The digital computer tracks workout stats such as Time, Distance, RPM (Cadence), Speed, Calories Burned, and Heart Rate. But the heart rate data can only be displayed when the handles with the HR sensors are grasped during a workout.  

The data are displayed with good readability but could diminish when viewed in a poorly-lit room because the monitor is not backlit.  

There is a Race Mode feature that allows you to set the Time and Distance you wish to target, and you can also set up goals for Time, Distance, and Calories Burned.  

Interestingly, unlike some display computers, this one offers the opportunity to set Distance, and Speed measurement units in either miles or km and mph or km/h, respectively. 

There are 3 easy-to-use navigation buttons that include Mode, Set, and Reset.

The Mode button is used to select the function displayed or during setting mode; the Reset button is used to reset function value, while the Set button is used to set up the target Value of Target, Distance, Calories, and Time.  

Finally, the monitor is powered by 2 AAA batteries (included).  


The Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike features a tablet holder, a water bottle holder, and dumbbell holders that can hold up to 20 lbs./9 kg each.  

The dumbbells are not included. You will have to purchase them separately if you wish to use them.  


The Synergy Pro SF-B1851 is not a large machine, therefore, it won’t overwhelm your space. Its length and width measurements are 49’’ and 22’’, respectively. What this means is that a storage area with perimeters of 4’1’’ length by 1’9’’ width should be accommodative.  

Due to the front-mounted transport wheels, relocating or moving the bike around the apartment won’t be a problem regardless of its weight.  

Pros/Features Overview 

  • It is constructed with an anti-corrosive steel frame, and ABS made drive train cover 
  • Users up to 300 lbs./136 kg can utilize it 
  • The base framework features adjustable levelers for stability on a surface that is not even
  • The pedals are dual-sided, they support standard gym shoes and clip-in shoes 
  • The cushioned 4-way adjustable seat provides decent comfort 
  • Users with inseams (inner thigh to ankle length) of 29’’-39.5’’ can be accommodated  
  • The multi-grip handlebar is ergonomically designed and cushioned for comfortable and secure grips 
  • The drive is bi-directional; you can pedal in reverse 
  • The integrated heavy flywheel maintains stable and vibration-free motion 
  • Due to the magnetic resistance system and the belt drive, the bike’s operation is smooth and quiet 
  • Goal settings for Time, Distance, and Calories 
  • The multiple digital monitor tracks workout progress by displaying stats such as Time, Distance, Speed, Cadence (RPM), and Heart Rate 
  • Race Mode setting; 
  • EKG contact grips; 
  • Transport wheels included for easy relocation 
  • Water bottle holder included for hydration 
  • Tablet holder included for entertainment purposes 
  • Easy assembly 
  • Low maintenance requirement 


  • The monitor is not backlit 
  • The console is not telemetric 
  • The resistance levels are not predefined 
  • No online app connectivity 



  • 3 Years for the Frame 
  • 180 Days for Parts and Components 

Product Dimensions and Specifications 

  • Length: 49’’ 
  • Width: 22’’ 
  • Height: 46.5’’ 
  • Shipping dimensions: 41.5’’ L x 10’’ W x 34.6’’ H 
  • Net weight: 111.3 lbs./50.4 kg 
  • Gross weight: 125.9 lbs./57 kg 
  • Maximum user weight capacity: 300 kg/136 kg 
  • Supported inseams: 29’’-39.5’’ 
  • Frame: Steel 
  • Seat: 4-way adjustable 
  • Handlebar: 2-way adjustable 
  • Pedals: Dual-sided 
  • Drive: Belt 
  • Resistance: Manual magnetic, infinite adjustable levels 
  • Flywheel: 40 lbs./18 kg 
  • Console/monitor: Mid-range LCD  
  • Heart rate monitoring: Contact grips 
  • Dumbbell holders included 
  • Water bottle holder included 
  • Tablet holder included 


The shipping of this bike is free by Amazon, and it’s delivered in a couple of days.  

It arrives in a single box that weighs 125.9 lbs./57 kg, with dimensions of 41.5’’ long by 10’’ wide by 34.6’’ high.  


The Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike is mostly preassembled; only a few parts are needed to be attached upon arrival.

An average skilled person can successfully assemble the bike in less than an hour.


As aforementioned, no serious maintenance is needed, other than making sure that the bike is kept clean at all times. Inspect it before use to ensure that the parts are not compromised.  

It is ideal to store it in a cool, dry, and dust-free area.  


The Sunny Health & Fitness SF-B1851 Synergy Pro Indoor Cycling Bike has some compelling useful features that could directly or indirectly help you to transit to better physical well-being.  

It supports a maximum user weight capacity of 300 lbs./136.  

The mid-range console features an LCD monitor that tracks multiple workout data simultaneously, and it offers the opportunity to set the measurement units of Speed, and Distance in either mph or km/h, and miles or km, respectively.  

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