Sunny Health & Fitness Synergy SF-B1879 Indoor Cycle

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Sunny SF-B1879

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L: 49"
275 lbs30 lbsManual

The Sunny Synergy SF-B1879 is one of the indoor cycling bikes with magnetic resistance released by Sunny Health & Fitness in 2020. Although it’s a trainer made for home use, it has a pretty solid construction and comes with a small performance monitor. In terms of features, it can be compared with the Efitment IC038 but has a slightly slimmer seat and its flywheel is a bit heavier.

Key Features and Specifications

  • Assembled dimensions: 49L x 22W x 50.5H inches (124L x 56W x 128H cm)
  • Assembled weight: 88.2 lbs (40 kg)
  • Flywheel weight: 30 lbs (13.6 kg)
  • Weight capacity: 275 lbs (125 kg)
  • Seat: 4-way adjustable
  • Drive: Belt
  • Resistance: Manual magnetic
  • Performance monitor: Time, distance, total distance, speed, RPM, calories, pulse, scan
  • Extras: Bottle holder, device holder, dumbbells holder
  • Warranty: Frame 3 years / Parts 180 days

Frame construction

The Sunny Health & Fitness Synergy SF-B1879 indoor cycling bike features a heavy-duty triangular frame made of steel tubing. It combines oval and rectangular bars in its construction for improved aesthetics. Their joints are precision-welded and the seat bar goes all the way to the median base bar, being welded to it for improved overall sturdiness. The only major non-metallic part in the bike’s construction is the drivetrain guard which is made of durable thermoplastic material.

The bike’s frame also integrates a step-up bar. This is the small horizontal tube that connects the seat tube with the main oblique tube. This can help a shorter user with mounting and dismounting but can also serve as a support point for stretching or various spin workouts that require you to repeatedly mount and dismount. Not all spin bikes have this feature, so it is a plus.

The bike is a few inches larger than other models, but just as most other spin bikes, it doesn’t take too much space. It is approx. 49″ (124 cm) long, and 22″ (56 cm) wide, while its highest point is at approx. 50.5″ (128 cm) above floor level when the handlebar is fully extended. It is recommended, though, to allow at least two feet of clearance all around it for ease of access.

The fully assembled bike is fairly heavy. Its net weight is approx. 88.2 lbs (40 kg). This being said, the packaged unit should be carried by two people. However, once the bike is assembled, it can easily be moved by only one person as its front base bar has a set of small wheels. Also, it’s important to mention that both base stabilizers have adjustable levelers.

All the steel tubes in the bike’s frame construction are coated with a corrosion-resistant paint finish. The main color used is gray, the only exceptions are the seat and handlebar posts which are black, while the flywheel is chrome-plated.

Seat and handlebars

The Sunny Health & Fitness SF-B1879 indoor cycle includes a high-comfort saddle. It is a bit wider than the average spin seat and integrates a layer of foam cushioning. It also has a long median groove for extra breathability.

It’s important to mention that the saddle has a standard, collar-type attachment system. This means you can slightly tilt it forward or backward. It also means that it can easily be replaced, if necessary, and compatible replacements for it should be available in most bike shops.

The bike’s seat is four-way adjustable (front, back, up, down). It features two large knobs, easy to grip and turn. Its upright post has several adjustment positions and offers an adjustment span of approx. 10″ (25.4 cm), for an inseam between 27″ (68.5 cm) and 37.5″ (95.2 cm). The bike’s horizontal slider also offers 4.5″ (11.4 cm) of front to back adjustment. Therefore, the bike should be able to accommodate users between 5’0″ and 6’5″ (153 – 196 cm) with no problem, allowing a complete range of motion. It is also rated for a maximum user weight limit of 275 lbs (125 kg) which evidently applies to the seat too.

The Sunny Synergy SF-B1879 exercise bike features a multi-grip handlebar. It offers the possibility to adopt a standard grip, a racing grip, a climbing grip, and an aero grip. Unlike the seat, it is only two-way adjustable. It does not have a horizontal slider.

The bike’s handlebar is covered by a layer of high-density foam material to provide a comfortable and secure grip. Its side grips integrate metallic pulse sensors and the included performance monitor has a pulse tracking function. The base section of the aero bar features a small ABS cover which can serve as a phone or tablet holder.

Resistance and drive

The Sunny Health & Fitness Synergy SF-B1879 indoor cycling trainer is equipped with a manual magnetic resistance system similar to the HMC Athlete 5006. It consists of a magnetic brake attached to the tension knob on top of the main tube of the frame. As you turn the knob clockwise, the magnetic brake moves closer to the flywheel which increases the magnetic drag and the overall pedaling difficulty. The knob can also be pressed down to stop the flywheel from spinning.

Since the bike’s braking system is manual, the bike does not require an adapter or an external power source. But on the other hand, it does not adjust the resistance automatically. Also, the included performance monitor does not have pre-set programs.

Although the bike has a magnetic brake, it does not have pre-determined steps or levels. You simply tighten it until you get the desired pedaling difficulty. The main advantage of a magnetic brake is that the brake pad does not touch the flywheel and the pedaling motion is very smooth and quiet.

The bike is equipped with a heavy-duty 3-piece crankset similar to a mountain bike crankset. It features solid steel crank arms and metallic pedals. Therefore, it can support the whole weight of the user as long as they don’t exceed the specified 275 lbs (125 kg) weight limit.

The pedals do not have SPD elements for spin shoes, but they do have adjustable toe cages in case you want to secure your feet on them. Their threads are 9/16″, though. So, replacements for them are widely available.

This Sunny Health & Fitness indoor cycling bike is equipped with a 30-lbs (13.6 kg) chrome-plated flywheel featuring ABS side covers. It is perimeter-weighted for improved inertia. It also allows pedaling in reverse, but due to the simple drivetrain construction, you cannot coast on the bike. When pedaling in reverse, you will get the same pedaling resistance as when pedaling forward.

The bike is equipped with a belt drive system. It uses a heavy-duty poly-v rubber belt. This type of drive system comes with a few advantages. For example, as opposed to a chain drive, you don’t have to lubricate it. Also, it contributes to the overall quietness and smoothness of the ride.

Performance monitor

The Sunny SF-B1879 indoor cycle includes a basic performance monitor. It features an LCD display (without LED backlight) that tracks time, distance, total distance, speed, RPM, calories, and pulse. Speed and distance are shown in MPH and miles; there is no option for setting them to km/h and kilometers. Also, for the pulse reading function, you will have to hold on to the sensors integrated into the handlebars; the monitor unit is not telemetric, so it cannot track your pulse from an HR chest strap.

The performance monitor unit is easy to use. It has only one button (MODE). You can press it repeatedly to select the workout metric that you want to view, or you can select the Scan Mode which rotates all the metrics. As we’ve mentioned above, the unit does not have pre-set workout programs, nor it has goal settings. The Mode button also has a reset function. You can press and hold it for a few seconds to clear all the values to zero.

The monitor unit requires two AAA batteries as its power source. It starts up when you begin to pedal and also automatically turns off after four minutes of inactivity on the bike.

Assembly and Maintenance

The bike’s body comes pre-assembled, with the flywheel, drivetrain, brake, and crankset already attached. You only need to add the two base stabilizers, the seat post, the saddle, the handlebar post, the handlebar, the pedals, and the performance monitor. This shouldn’t take more than 30 minutes. All the necessary tools for the task are included and the manual provides clear assembly instructions.

Since it’s a belt-drive bike, its transmission does not require any lubrication. Therefore, all you have to do for maintenance is periodically check for loose bolts and parts. Also, since the bike uses a magnetic brake, you don’t have to worry about its wear and tear, or about replacing the brake pad.

The Pros

  • Heavy-duty steel frame – 275 lbs weight capacity;
  • Aesthetic design;
  • Adjustable stabilizers on both bases;
  • Transport wheels included;
  • 4-way adjustable seat;
  • Cushioned saddle with a median groove for breathability;
  • Multi-grip handlebar with pulse sensors;
  • Smooth and silent belt drive;
  • Perimeter-weighted flywheel for enhanced inertia;
  • Magnetic resistance, with zero friction;
  • Performance monitor included – it can track time, distance, total distance, speed, RPM, pulse, and calories burned;
  • Bottle holder included;
  • Device holder included;
  • Dumbbell holder included;
  • Easy to assemble;
  • Little maintenance required.

The Cons

  • No backlight on the performance monitor display;
  • The pulse and calories readings aren’t super accurate.


The Sunny Health & Fitness Synergy SF-B1879 is an indoor cycling bike made for home use. It is equipped with a manual magnetic resistance system, a 4-way adjustable seat, a 30-lb perimeter-weighted flywheel, and a performance monitor that tracks all the important workout metrics. It also has a pretty sturdy construction with a weight capacity of 275 lbs. It’s a great stationary bike for high-intensity spin workouts, muscle toning, stamina and strength development, interval training, and weight loss.

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