Sunny Health & Fitness SF-B1877 Indoor Cycling Bike

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Sunny SF-B1877

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L: 48.8"
265 lbs29 lbsManual

The Sunny SF-B1877 is one of the indoor cycling bikes released by Sunny Health & Fitness in 2020. In terms of features, it is similar to the Sunny SF-B1879, but the design of its frame is a bit different, while its maximum user weight limit is slightly lower. It also lacks the dumbbell holder.

Key Features and Specifications

  • Assembled dimensions: 48.8L x 20.1W x 48H inches (124L x 51W x 122H cm)
  • Assembled weight: 83.7 lbs (38 kg)
  • Flywheel weight: 29 lbs (13 kg)
  • Weight capacity: 265 lbs (120 kg)
  • Seat: 4-way adjustable
  • Drive: Belt
  • Resistance: Manual magnetic
  • Performance monitor: Time, distance, total distance, speed, RPM, calories, pulse, scan
  • Extras: Device holder, bottle holder
  • Warranty: Frame 3 years / Parts 180 days

Frame construction

The Sunny Health & Fitness SF-B1877 indoor cycle features a steel frame combining rectangular and oval tubes in its construction. The frame has a triangular design for improved sturdiness but as opposed to the Sunny SF-B1879 model, its base longitudinal bar and the main tube of the frame are slightly curved. All the steel tubes in the bike’s construction are coated with a corrosion-resistant paint finish. The colors used are gray for most of the frame and black for the posts of the seat and handlebars. The flywheel is chrome-plated.

Of course, the bike also integrates several thermoplastic parts in its construction. For example, the brake cover and the drivetrain cover are made of durable plastic material. The side panels of the flywheel are also plastic-made.

The fully assembled bike is a bit larger than the average spin bike made for home use. With all the parts assembled, it is approx. 48.8″ (124 cm) long, and 20.1″ (51 cm) wide. However, it is recommended to leave at least two feet of clearance all around the bike for safe usage and ease of access.

The bike is not extremely heavy but does weigh approx. 83.7 lbs (38 kg). Therefore, it is recommended to be transported by two persons. But nonetheless, once it is assembled, it can easily be moved by only one person. Its front base stabilizer features a set of transport wheels. Also, both base stabilizers of the bike feature adjustable levelers.

One last aspect to mention here regards the bike’s step-up bar. Not all spin bikes have this element, so it’s a plus. It 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.

Seat and handlebars

The Sunny SF-B1877 indoor cycling trainer includes a pretty standard saddle. Its top is constructed on a hard plastic (probably nylon) shell, with a top layer made of high-density foam material. It lacks the central cropping that more expensive bike seats have, but does have a bit of contouring for breathability. It has a standard collar-type attachment system, though, so not only that you can easily remove it, replacement models compatible with the bike should be available in any bike shop.

The seat offers four-way adjustability (up, down, front, back). Its upright post offers an adjustment span of approx. 9″ (22.8 cm), for users with an inseam between 27.5″ and 36.5″ (70 – 93 cm). The horizontal slider adds approx. 5″ (12.7 cm) of front to back adjustment. Therefore, the bike should accommodate users up to 6’5″ (196 cm) with no problem. It’s also rated for a maximum weight capacity of 265 lbs (120 kg).

The bike is equipped with a multi-grip handlebar. It allows a climbing grip, a parallel grip, a standard grip, and a close grip. It also has a long loop bar in the middle offering the possibility to adopt an aero grip. Its side grips integrate metallic pulse sensors and the included fitness monitor has a pulse reading function.

The bike’s handlebar lacks the horizontal slider feature, so it’s adjustable only up-down. Its post offers several inches of adjustment. The whole handlebar assembly is covered by a layer of high-density foam material for an improved and comfortable grip. Also, the top plastic cover of the handlebar can serve as a phone holder or tablet holder.

Drive and resistance

The Sunny Health & Fitness SF-B1877 indoor cycle is equipped with a fairly heavy flywheel. It weighs 29 lbs (13 kg) and has a perimeter-weighted structure. The perimeter-weighted design is meant to provide extra inertia which leads to a consistent pedaling momentum, great for spinning workouts.

The flywheel is also bi-directional. In other words, the bike offers the possibility to pedal in reverse. However, just as for any other spin bike, coasting is not possible. When pedaling in reverse, you will get the same resistance as when pedaling forward.

The bike uses a belt for its transmission. The belt drivetrain comes with several advantages. First of all, it generates less vibration than a chain so the bike delivers a very smooth and quiet pedaling motion. And second of all, it does not require lubrication.

Since it’s a bike made for spinning workouts, the Sunny SF-B1877 is equipped with a heavy-duty, 3-piece crankset. It features long arms and a fairly narrow (177.8 mm) Q-Factor. This narrow spacing between the pedals reduces the lateral stress on the knees and ankles during pedaling leading to a more comfortable pedaling motion.

The included pedals are made of aluminum alloy with rubber inserts on the edges for an improved grip. They 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. They also have standard 9/16 threads, so you can find compatible pedals in any bike shop if you will ever want to replace them.

The Sunny Health & Fitness SF-B1877 indoor cycling bike is equipped with a manual magnetic resistance system. This being said, the bike cannot adjust the resistance automatically. Also, you don’t need a power adapter or an external power source for it.

The resistance system consists of a magnetic brake attached to the main tube of the bike’s frame above the flywheel. The magnetic brake is connected to the tension knob on top of the bike’s frame. Therefore, when you turn the knob, you adjust the distance between the brake pad and the flywheel which increased or decreases the pedaling difficulty.

The bike’s brake is stepless; there are no pre-determined tension levels on the resistance adjustment knob. But as a general idea, on the lowest difficulty setting, the bike provides a pedaling resistance similar to riding a bike on a straight road, while on the highest difficulty it simulates a steep climb.

Fitness monitor

The Sunny SF-B1877 exercise bike comes with a basic fitness monitor. It features an LCD display that tracks time, distance, total distance, speed, RPM, calories, and pulse. Speed and distance are shown in MPH and miles; you cannot set them to metric units. 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 unit’s display does not have LED backlight.

The bike’s fitness monitor has only one button (MODE). You can press it repeatedly to select the desired workout metric, or you can select the Scan Mode which rotates all the metrics showing each one for approx. 6 seconds. The button also covers the monitor’s reset function. You can press and hold it for a few seconds to clear all the values on it to zero. It does not have pre-set programs and you cannot set workout targets for distance, time, or calories.

The monitor unit is battery-powered. It requires two AAA batteries which are included. It starts up when you press the button or when it detects flywheel movement. It also has a sleep mode which automatically initiates after approx. 4 minutes of inactivity on the bike.

Assembly and Maintenance

Most of the bike comes pre-assembled. You only have to attach the two base stabilizers, the seat post, the seat, the handlebar post, the handlebar, the device holder, the fitness monitor, and the pedals. This shouldn’t take more than 20-30 minutes. The task is fairly simple and the manual provides clear step-by-step assembly instructions. Also, all the necessary tools for the assembly are included.

For maintenance, you only have to keep the bike clean, wipe any sweat that may fall on the frame with a piece of cloth at the end of the workout, and periodically inspect the bike to make sure that all the parts are still functioning properly. Since the brake is magnetic, there’s virtually no wear and tear for the brake pad, so you don’t have to worry about its replacement. Also, the drivetrain uses a belt, not a chain, so it does not require periodic lubrication.

The Pros

  • Heavy-duty steel frame – 265 lbs weight capacity;
  • Aesthetic design;
  • Adjustable stabilizers on both bases;
  • Transport wheels on the front base;
  • 4-way adjustable seat;
  • 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;
  • Easy to assemble;
  • Little maintenance required.

The Cons

  • The fitness monitor does not have LED backlight;
  • The pulse and calories readings aren’t super accurate.


The Sunny Health & Fitness SF-B1877 is an indoor cycling bike designed to support any type of spin workout. It features a heavy-duty frame, a 29-lb flywheel, and a magnetic resistance system. It also includes a fitness monitor that tracks time, distance, total distance, speed, RPM, pulse, and calories burned. It’s a pretty solid bike, great for users of all levels, for high-intensity cardio workouts, muscle toning, interval training, stamina development, and weight loss. It’s also considerably more affordable than a commercial-grade bike, offering excellent value for the price.

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