Sunny SF-RB4850 Recumbent Bike | Easy on the Joints

Cycle into fitness with the Sunny SF-RB4850 Programmable Recumbent Bike by Sunny Health & Fitness. This recumbent bike supports riders up to 300 lbs in maximum user weight. Keep your workouts versatile in either a reclined or upright position with the multiple handrails. Take advantage of the step-through design to mount and dismount the cardio machine easily.

Sit comfortably on the full recumbent bike seat, equipped with breathable mesh back support. Use the easy-to-use seat adjustment lever to modify your distance from the pedals (leg inseam 30 inches to 40 inches). Grab the seat-level pulse grips to check your heart rate while exercising.

The Sunny SF-RB4850 recumbent bike has 16 levels of automatic magnetic tension, controlled through the console. Enjoy a smooth and quiet exercise experience, powered by a virtually maintenance-free belt-drive mechanism. Perform 13-inch strides that are easy on the joints when you rotate the 6.6-pound flywheel while providing you with a cardiovascular workout.

The SF-RB4850 features a color fitness console that tracks your time, speed, rotation per minute, distance, calories burned, pulse, and wattage. Take advantage of 12 preset workouts made for various fitness levels, built-in BMI calculator software, and additional target heart rate and wattage programs.

Learn more in my complete review below

Sunny SF-RB4850 Recumbent Bike
Sunny SF-RB4850 Recumbent Bike

Product: Sunny SF-RB4850 Recumbent Bike

Price: For a great deal on this bike, merely go here on Amazon

Warranty: Frame 3 years / Parts 180 days

My rating: 8.5/10

Amazon Affiliate Disclosure: I may earn commissions on purchases made through links in this post.

Details 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

SF-RB4850 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.

Sunny SF-RB4850 Recumbent Bike

All the steel parts in its construction come coated with a corrosion-resistant paint finish; the color used is black, this being the only color available for this model. Durable ABS covers also protect several frame parts (the seat base, for example).

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 advisable to leave at least two feet of clearance all around it.

The fully assembled bike is relatively 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 support integrates a lifting handle. Therefore, once constructed, only one person can quickly relocate it.

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


The Sunny SF-RB4850 comes 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).

Therefore, 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.

Sunny SF-RB4850 Recumbent Bike

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

The backrest features a heavy-duty ABS frame with a mesh structure for superior breathability and flexibility. It is approximately 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.

SF-RB4850 Handlebars

The bike comes 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 come 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 SF-RB4850 has 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 comes 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.

Sunny SF-RB4850 Recumbent Bike
Sunny SF-RB4850 Recumbent Bike

The bike offers 16 resistance levels. The 1-3 difficulty levels deliver a light resistance 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 time.

The internal flywheel weighs 6.6 lbs (3 kg). It’s not an extremely heavy flywheel so that this Sunny exercise bike is 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 comes 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 a durable ABS material. They integrate self-leveling elements and adjustable straps, so you can correctly secure your feet on them during pedaling. This can be a plus for users with specific disabilities.

SF-RB4850 Console

The Sunny SF-RB4850 recumbent bike comes with an LCD that divides into several sub-sections 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 relatively significant 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, 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.

Sunny SF-RB4850 Recumbent Bike

Workout programs

The console does not have Bluetooth or online connectivity but does 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 goals for 55%, 65%, 75%, and 85%.

Finally, P21-P24 are user-based programs. Differently put, up to four users can create their 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. This function will provide you with 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.

Sunny SF-RB4850 Recumbent Bike
Sunny SF-RB4850 Recumbent Bike

The HRC sticker is on the top section of the console. It shows the heart rate zones that you should aim for depending on your age, to benefit from a better aerobic output, fat burn, etc.

SF-RB4850 Assembly and Maintenance

The base frame of the bike comes 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 comes included with the bike.

Once 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 time). All you have to do is keep the unit clean and periodically check for loose parts.


  • Sturdy, steel frame – 300 lbs capacity;
  • Transport wheels on the front base;
  • Lifting handle on the rear plate;
  • Adjustable stabilizers on the backplate;
  • 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;

    Sunny SF-RB4850 Recumbent Bike
  • 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 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;
  • Reasonably easy to assemble;
  • Little maintenance required.


  • No online connectivity;
  • No USB charging port.

Sunny SF-RB4850 Recumbent Bike Summary

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.

I hope you found this article helpful and informative. If you have anything that you’d like to share or any opinions about my website, please do speak up. I look forward to your comments, questions, and the sharing of ideas.

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