Sunny Health & Fitness SF-RB4850 Recumbent Bike

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Sunny SF-RB4850

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300 lbsEddy
16 levels
Belt24 programs,

The Sunny SF-RB4850 is one of the recumbent bikes released by Sunny Health & Fitness in the second part of 2019. It’s a mid-range exercise bike featuring an automatic resistance system and a console with multiple workout programs. In terms of features, it can be compared with Circuit Fitness AMZ-587R; however, it offers several extra programs and lacks the USB port.

Key Features and Specifications

  • Assembled dimensions: 59L x 26W x 47.5H inches (150L x 66W x 121H cm)
  • Assembled weight: 87 lbs (39.4 kg)
  • Supported weight: 300 lbs (136 kg)
  • Drive: Belt
  • Resistance: Eddy current, 16 levels
  • Console: 24 programs
  • Extras: Tablet holder, bottle holder
  • Warranty: Frame 3 years / Parts 180 days

Frame construction

The Sunny Health & Fitness SF-RB4850 features a heavy-duty steel frame, combining rectangular, triangular, and cylindrical bars in its construction for improved sturdiness and aesthetics. All the steel parts in its construction are coated with a corrosion-resistant paint finish; the color used is black, this being the only color available for this model. Several frame parts (the seat base, for example) are also protected by durable ABS covers.

The bike is not extremely large, compared to other fitness machines. However, it still is 59″ (150 cm) long, and 26″ (66 cm) wide. Plus, it is recommended to leave at least two feet of clearance all around it.

The fully assembled bike is fairly heavy. It weighs approx. 87 lbs (~40 kg). So, it should be carried and assembled by two persons. Its front base does have transport wheels, though, and the rear base integrates a lifting handle. Therefore, once the bike is assembled, it can be easily relocated by only one person.

The rear base of the bike is equipped with two adjustable stabilizers. There is also one extra stabilizer at the middle of the median base bar, while the front base bar rests on two, non-adjustable rubber pads.

Seat and handlebars

The Sunny SF-RB4850 is equipped with an adjustable seat. The seat is attached to a rail system that allows you to move it closer or farther from the pedals. The rail offers an adjustment span of approx. 10″ (25.4 cm), for an inseam length between 30″ and 40″ (76 – 101 cm). This being said, the bike can accommodate users between 5’2″ and 6’5″ (157 – 196 cm) with no problem, allowing a complete leg extension and a correct range of motion.

The seat adjustment system is lever-based, which is quite a plus because you can adjust the position of the seat without having to get up. There is a lever on its right side which allows you to unlock it and re-lock it in the desired position.

It’s important to mention here that the backrest does not have a reclining system. It cannot be adjusted independently from the seat.

The seat is designed for superior comfort. Its base pad integrates approx. 2.5″ (6 cm) of foam cushioning. Its top combines vinyl and synthetic mesh material. It is also contoured for extra breathability.

The backrest features a heavy-duty ABS frame with a mesh structure for superior breathability and flexibility. It is approx. 20″ (50 cm) long, and 18″ (46 cm) wide, and slightly arched for extra comfort. It’s important to mention here that the backrest does not have a reclining system. It cannot be adjusted independently from the seat.

The bike is equipped with two sets of handlebars, one attaches to the seat assembly, the other to the front mast of the bike, under the console. The seat handlebars are equipped with metallic pulse sensors and the console has a pulse reading function and various HRC programs. The front handlebars have a simple design; they do not integrate any sensors.

Both handlebars feature rubberized grips for extra comfort. None of them are adjustable.

Drive and resistance

The Sunny Health & Fitness SF-RB4850 is equipped with an automatic magnetic resistance system. This means the bike can adjust the pedal resistance automatically. It also means that it requires an external power source. A power adapter is included with the bike.

The bike’s resistance system consists of an internal magnetic brake and a servo motor connected to the console. As you adjust the resistance from the console, or if the selected workout program adjusts the resistance automatically, the motor changes the position of the magnetic brake, increasing or decreasing the magnets’ pull.

The bike offers 16 resistance levels. The 1-3 difficulty levels deliver a light resistance, being recommended for exercising heart and lung function. Conversely, the top 15-16 levels allow you to achieve a higher calorie burn and an increased cardiovascular rate in a shorter period of time.

The internal flywheel weighs 6.6 lbs (3 kg). It’s not an extremely heavy flywheel, so this Sunny exercise bike can be used for recovery training. Most of its weight is placed in its perimeter, though. Thus, it provides a bit of extra momentum.

Many other exercise bikes with a magnetic resistance system feature a belt transmission, and the Sunny SF-RB4850 makes no exception. It is equipped with a durable poly-v belt. This type of drive system doesn’t require any lubrication. It also generates less vibration than a chain drive.

The bike’s crankset features heavy-duty steel arms. The pedals are made of durable ABS material. They integrate self-leveling elements and adjustable straps, so you can perfectly secure your feet on them during pedaling. This can be a plus for users with certain disabilities.


The Sunny Health & Fitness SF-RB4850 recumbent bike comes with the same console as the Sunny SF-E3912 elliptical trainer. This console features an LCD display divided into several sub-sections in order to show all the workout metrics at once, so you won’t have to use a Scan Mode to rotate them. The display also has LED backlight and fairly large digits, for improved readability.

The console display tracks all the important workout metrics, including time, RPM, speed, distance, total distance, calories, watts, and pulse. It is not telemetric, though. In other words, it does not have a built-in HR receiver, so it cannot communicate with any wireless HR chest strap. Therefore, in order to benefit from a pulse reading or use any of the HR workout programs, you have to use the sensors integrated into the seat handlebars.

The console does not have Bluetooth or online connectivity, but does offers 24 workout programs to keep you motivated. The P1 program is manual; it allows you to pedal and adjust the resistance freely throughout your workout. It also offers the possibility to select goals for time, distance, and calories.

The P2-P13 programs are preset. Their segment layout targets different types of workouts. Some are interval workouts, others are focused on weight loss, while others have a hill or peak layout.

The P14 program is for watt control while P15 is a Body Fat program. For P14 you can select a watt value and the console will auto-adjust the resistance to keep you within that target. The Body Fat program calculates your body mass index (BMI) based on your age, weight, height, and gender input. It will also generate a custom program according to your BMI.

The console also has five heart rate programs (P16-P20). The P16 program allows you to select a custom heart rate target, while the P17-P20 programs have preset targets for 55%, 65%, 75%, and 85%.

Finally, P21-P24 are user-based programs. Differently put, up to four users can create their own custom program, save it, and re-use it every time they want.

The unit also has a pulse Recovery function. This gives you the possibility to determine your fitness level based on your pulse recovery at the end of your workout. If this function is initiated, the console will give you a fitness rating between F1 (excellent) and F6 (poor).

Two other notable console features are the tablet holder and the HRC sticker. The tablet holder consists of a small shelf that can hold your tablet or smartphone. The console does not have a USB port for charging your device, nor it has a sound system. The HRC sticker is placed on the top section of the console. It shows the heart rate zones that you should aim for depending on your age, in order to benefit from a better aerobic output, fat burn, etc.

Assembly and Maintenance

The base frame of the bike come in one piece, with all the drive and resistance parts pre-assembled. However, the rest of the parts do require user assembly. You will have to attach the base bars, the seat, the console mast, the front handlebars, the console, and the pedals. This may take more than an hour, but the process is far from being complicated. Plus, the manual provides excellent, step-by-step assembly instructions and a set of tools for the task is included.

Once the bike is fully assembled, you don’t have to worry too much about maintenance. The internal parts don’t require any lubrication (or at least they shouldn’t for a very long period of time). All you have to do is keep the unit clean and periodically check for loose parts.

The Pros

  • Sturdy, steel frame – 300 lbs capacity;
  • Transport wheels on the front base;
  • Lifting handle on the rear base;
  • Adjustable stabilizers on the rear base;
  • Step-through frame design for easy access to the seat;
  • Seat handlebars with pulse sensors;
  • Cushioned and contoured seat;
  • Flexible mesh backrest for extra breathability;
  • Lever-based rail adjustment system for the seat;
  • Weighted pedals with adjustable straps;
  • Eddy current resistance system;
  • 16 resistance levels available;
  • Mid-range console with an LCD display which can track time, distance, speed, RPM, Watts, calories, and pulse;
  • 24 workout programs;
  • Recovery function;
  • Tablet holder included;
  • Bottle holder included;
  • HRC sticker on the console;
  • Fairly easy to assemble;
  • Little maintenance required.

The Cons

  • No online connectivity;
  • No USB charging port.


The Sunny Health & Fitness SF-RB4850 is a mid-range recumbent bike made for home use. It features a durable frame, an automatic magnetic resistance system with 16 levels, and 24 workout programs on the console. It also offers excellent micro-adjustability and comfort. It’s a great exercise bike for light to medium-intensity cardio workouts, muscle toning, and weight loss. It’s also one of the most affordable recumbent bikes with automatic resistance.

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1 thought on “Sunny Health & Fitness SF-RB4850 Recumbent Bike”

  1. Christian parcell

    Well I just received the bike and I put it together it seems very sturdy and I can pedal but I cannot figure out where you would plug the monitor in there are two holes in the back one for heart rate and one for something else but the pug that I have does not fit in those holes I’m not sure if that’s where it goes or not looking to find out how to turn it on

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