Sunny SF-RB4850 Recumbent Bike | Micro-Adjustability & Comfort

Cycle into fitness with the Sunny SF-RB4850 Recumbent Bike by Sunny Health & Fitness. This recumbent bike supports riders up to a maximum user weight of  300 lbs (136 kg). Keep your workouts versatile in either a reclined or upright position with multiple handrails. Take advantage of the step-through design to quickly mount and dismount the cardio machine.

Sit comfortably on the fully recumbent bike seat 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, quiet exercise experience powered by a virtually maintenance-free belt-drive mechanism. Perform 13-inch strides while rotating the 6.6-pound flywheel. That’s easy on the joints while providing you with a cardiovascular workout.

The SF-RB4850 features a color fitness monitor that tracks your time, speed, rotation per minute (RPM), distance, calories burned, pulse, and wattage. In addition, 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 to Sunny Health &

Warranty: Frame 3 years / Parts 180 days

My rating: is 9/10

Affiliate Disclosure: As a Sunny Health & Fitness Affiliate Program participant, I earn commissions on purchases made through links in this post. Full disclosure

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
  • Fitness Monitor: 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, black. In addition, durable ABS covers 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. Therefore, leaving at least two feet of clearance all around it is advisable.

The fully assembled bike is relatively heavy. It weighs approx. 87 lbs (~40 kg). So, two people should carry and build the bike. In addition, 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. In addition, there is also one extra stabilizer in the middle of the median base bar, while the front 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 seat’s position without getting up. In addition, a lever on its right side allows you to unlock it and re-lock it in the desired position.

Sunny SF-RB4850 Recumbent Bike

The seat is for superior comfort. Its base pad integrates approximately 2.5″ (6 cm) foam cushioning, and 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, 18″ (46 cm) wide, and slightly arched for extra comfort. Unfortunately, the backrest does not have a reclining system. Therefore, it cannot adjust 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, and under the fitness monitor. The seat handlebars come equipped with metallic pulse sensors, and the monitor has a pulse reading function and various HRC programs. However, the front handlebars have a simple design; they do not integrate any sensors.

Both handlebars feature rubberized grips for extra comfort. Unfortunately, none of them are adjustable.

Drive and resistance

The Sunny SF-RB4850 has an automatic magnetic resistance system. Thus, the bike can adjust the pedal resistance automatically. Unfortunately, it also requires an external power source, and a power adapter comes with the cycle.

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

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.

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

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

SF-RB4850 Fitness monitor

The Sunny SF-RB4850 recumbent bike has a fitness monitor that divides into several sub-sections to show all the workout metrics, so you won’t have to use a Scan Mode to rotate them. In addition, the LCD also has an LED backlight and relatively significant digits for improved readability.

The fitness monitor 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, you must hold the sensors integrated into the seat handlebars to benefit from a pulse reading or any HR workout programs.

Workout programs

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

Unfortunately, the fitness monitor does not have Bluetooth or online connectivity but does have 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. In addition, it also allows selecting 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 monitor will auto-adjust the resistance to keep you within that target. The Body Fat program calculates your body mass index (BMI) based on age, weight, height, and gender input. It will also generate a custom program according to your BMI.

The fitness monitor 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 reuse it whenever they want.

In addition, the monitor also has a pulse Recovery function, which allows you to determine your fitness level based on your pulse recovery at the end of your workout. This function will provide 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 has a small shelf that can hold your tablet or smartphone. Unfortunately, the fitness monitor does not have a USB port for charging your device, nor does its sound system.

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

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

SF-RB4850 Assembly and Maintenance

The bike’s base frame 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 fitness monitor, and the pedals.

Therefore, it may take more than an hour of your time, 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 with the bike.

Once assembled, you don’t have to worry too much about maintenance. The internal parts don’t require lubrication (or at least they shouldn’t for a very long time). So 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 the 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 fitness monitor with an LCD that can track time, distance, speed, RPM, Watts, calories, and pulse;
  • 24 workout programs;
  • Recovery function;
  • Tablet holder included;
  • The bottle holder included;
  • HRC sticker on the console;
  • Reasonably easy to assemble;
  • Little maintenance is required.


  • The fitness monitor does not have online connectivity;
  • The fitness monitor does not have a USB charging port.

Sunny SF-RB4850 Recumbent Bike Summary

The Sunny Health & Fitness SF-RB4850 is a mid-range recumbent bike for home use. It features a durable frame, an automatic magnetic resistance system with 16 levels, and 24 workout programs on the fitness monitor. It also offers excellent micro-adjustability and comfort.

Moreover, 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 motorized resistance.

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

Please remember that you should consult your physician to determine if you have any medical or physical conditions that could risk your health and safety or prevent you from using the equipment properly. In addition, your physician’s advice is essential if you are taking medication that affects your heart rate, blood pressure, or cholesterol level.

10 thoughts on “Sunny SF-RB4850 Recumbent Bike | Micro-Adjustability & Comfort”

  1. For one thing, I love the structure of this Sunny SF-RB4850 Recumbent Bike. It feels perfect, and I can always resonate better with it and how it works.  The comfort that comes with making use of this tool can help achieve balance during a workout and also ensure that we make the very best use of it. Good one here

  2. Hello there, thanks a lot for sharing this wonderful piece of information here with us. I must say I really did enjoy going through your review. I have used several recumbent bikes before, and they are really great for work out; this one looks pretty comfortable to use. I will share this with my gym instructor; maybe he could get one, thanks.

  3. Why do the columns of rectangular boxes, flash during the workout, proceeding from left to right, across all ten columns?
    Can each user come back and continue his workout?

    • Hello John, thanks for your inquiry. The columns of flashing lights are showing the resistance level of the program and the time remaining. The higher the column gets, the stronger the resistance. When the flashing lights get all the way to the right side of the console and stop flashing, the program is over. The programs usually last for 30 minutes. Your next question and I am not 100% positive about. I don’t believe the console has a pause function, so you would have to start over when it shuts off. I hope this helps explain your questions. However, if you require more help, use this link to Sunny Health and Fitness. Fill out the form with the required information and give the model number and serial. They will get back to you ASAP.

  4. I need a home bike, and this one is an excellent choice! I love the design with its front wheels. As I am tiny, I need one that is easy to move around my house! Also, I get a lot of features for a very affordable price, and it seems like a quality bike as well. Thank you for this review; it helps a lot to make a decision. The plus is that it doesn’t have a lot of « cons.» That’s nice!!

    • Hi there, thanks for stopping by. Would you please let me know if I can assist in any way? I’d be happy to help.

      Kind regards, Robert

  5. Hi, and thanks for sharing this. We have been looking for exercise equipment, and a recumbent bike has several attractions. Firstly our basement space has quite a low ceiling. One problem with other exercise equipment is that I can easily end up ducking to avoid banging my head on beams in the ceiling. This makes a recumbent bike or rowing machine a logical choice. However, I’ve learned to avoid rowing since I have a bad back and can easily injure myself in that area. The last experience I had with recumbent bike exercise machines was the physiotherapy course I took after knee replacement surgery. The recumbent bike was always where I finished the sessions and gave me the right workout for cardio without risking pulling a muscle or getting sore in my lower back which is the problem I have in the regular upright cycling position. Thanks again; understanding the features and pros and cons is exactly the sort of analysis I need to do. Best regards, Andy 

    • Hi Andy, thanks for stopping by and sharing with us. Would you please let me know if I can ever be of assistance? I’d be happy to give you some more suggestions to consider.

      Kind regards, Robert

  6. The Sunny SF-RB4850 Recumbent Bike sounds like a bike that would be good for me. I have to keep an eye on my heart rate as I exercise. I have an unusually high heart rate. Having the LCD dashboard is a feature that would be helpful when working out so I could measure what is right and what is wrong with my workouts.

    I like that you can adjust for longer legs, which makes it more convenient for those of us who are tall. I like all of the features of this bike and will be looking at it for a solid physical exercise machine purchase and investment. We all need to invest in our health.


    • Hi Jerry, thanks for stopping by. Would you please let me know if I can ever assist you with any exercise equipment? I’m glad to be of help.

      Kind regards, Robert


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