Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike Review

The Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike comes with a lot to like about it.

The dual pedals, the monitor, media device holder and dumbbell holder being good extras in addition to the belt drive, magnetic resistance and 40 lbs flywheel.

It looks fine if a little plain with the standard indoor bike look, the silver coloring and without the red flywheel to add contrast.

But it is more than looks that are important with an exercise bike for home cardio workouts.

It is about it being able to provide a reliable platform to get those fitness benefits.

First up is to check out how well it can stand up to the intensity of the indoor cycling and spinning type workouts.

In a hurry? >>>


It has a heavy duty steel frame and stabilizer bars to provide a good platform for all users up to 300 lbs weight. It should hold steady without any rocking movement at any level of intensity in and out of the steady and when transitioning between.

At the ends of the stabilizer bars are levelers to help balance up the bike if the floor is not completely level to prevent any rocking.

The bike should be stable on all floor types including carpet except for the plush types where it may not settle properly.

You may want a mat to protect the floor from scratching or dents and sweat that may drop when you are working out hard..

The reviews that have been published on Sunny’s site indicate that customers believe the bike is solid and that it is durable with them expecting to get a lot of use from the bike.

It appears there may have been an issue with the pedals or wheel bearing that Sunny have worked with customers to sort. It would seem from reviews that it may have been fixed.

The bike warranty is okay with 3 years for the frame and 180 days on parts and components. This normally doesn’t include labor to add a replacement part with the customer expected to do that. If there is a problem then Sunny seem to work to sort the issue. But, usually there won’t be an issue to sort based on the performance of other bikes in Sunny’s range.


The seat can be moved up/down and backwards/forwards this allows you to get the best positioning of the legs in relation to the pedals and in relation to handlebars. The bike fits with an inseam between 29 ins and 39.5 ins (measured from top of inner thigh and bottom of the foot). Customers between 5ft and 6 ft 2 ins have used the bike successfully.

The handlebars don’t have as much adjustment with them only being able to be moved up and down. This means you can get the height you want but may find that even with the seat adjustment they aren’t just in the right position but most will find the fit adequate.

The distance between the seat and handlebars can be adjusted between 15.5 ins and 19.5 ins to help accommodate your upper body.

The adjustments are made by loosening the adjustment knobs, pulling them and then sliding the handlebars or seat to the position you want re-inserting the pop-pin in the closest pre-set hole and tightening in place. You shouldn’t have any slipping when being used..

Making these adjustments is straightforward and quick – not as quick as those with the handle adjustments and you won’t get the exact point you want due to the pre-set holes. But these aren’t enough to slow you down too much or getting a good fit.

If you are likely to be sharing the bike with others the adjustment won’t really get in the way of a good workout. There are makings on the posts to help to put back to your setting if moved and you can use a permanent marker on the post as a guide.

Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike Resistance

The bike’s magnetic resistance is controlled by a tension knob at the front of the frame. You turn it right (clockwise) to increase the resistance and left to decrease it.

The magnets are in a block above the flywheel. The magnets move closer to the wheel to increase the tension on the wheel and away to decrease.

They don’t touch the wheel. Due to this there is no wear and tear making it low maintenance and quiet as there is no rubbing noise.

The change in the resistance is incremental and you can set it to the level you want and change as required. There is no markings or measurement of resistance levels to help you to set it at the level you want or to return to a previous setting.

To get to the level you want you need to do this by feel and estimate. One way to get started is to count how many turns it takes to get from the easiest setting to hardest and using that as a rule of thumb to let you know when you are at a percentage of hardness.

Also, you can find the setting that feels like you are pedaling on a flat road as a starting point.

If you are new to indoor cycling it only takes a short period of time to work it out and then you should be set. Still it would be good to have it shown like it does with the Schwinn IC4 but you have to pay extra for that bike (and if you want to use with the Peloton Digital App the levels don’t match up but can be converted with a little give and take).

The upper resistance level for most people should be hard enough to get a tough workout but those who are hardened cyclists or indoor cyclists may want to look for something tougher as you can get with friction pad resistance.

Drive Type

The bike comes with a belt drive.

Unlike a chain drive you don’t need to be tightening or lubricating in a similar way to using a road bike. You also miss the clinking and the slight variation as the chain turns over the sprockets. It does miss out on some of the road bike feel.

Instead it’s very quiet, smooth and low maintenance. A belt drive will eventually stretch after a number of years. Changing it will need normally need specialist tools.

The drive is enclosed which protects it from damage and dust. Also, it protects small fingers, legs and pets from being hurt.

Along with the 40 lbs flywheel it helps to provide a smooth and consistent feel to your exercise even with the resistance up high in or out of the saddle (seat). You shouldn’t experience variation as the flywheel pulls the pedals through to prevent an up/down motion to the pedaling which can add some impact to pedaling.

It has a fixed gear. This means when the flywheel is turning so are the pedals. You can’t freewheel or coast with pedals continually turning until you bring them to a stop by slowing down with your feet on the pedals or by pushing down hard on the tension knob to use it as a brake on the flywheel. It is important to bring the pedals to a stop before you try to get off otherwise you may get a painful whack by the pedals and might injure yourself.


The bike comes with dual pedals with toe cages on one side and SPD fittings on the other. This allows the bike to be used with athletic shoes or specialist cycling shoes without changing the pedals allowing for different requirements and experience.

The toe cages come with adjustable straps to allow it to fit a range of feet sizes and to tighten them up to get a good secure fit to prevent your feet from slipping or moving as you pedal.

When getting started you can just use tennis shoes and get a good workout. Later on you can get SPD shoes if you want to get a better connection and a more effective indoor cycling workout.

This dual nature allows people with SPD shoes and those without to share the bike easily.


Seat You may find the seat too hard for your sit bones especially if you haven’t been on a bike or indoor cycle for a long period of time.

The seat is shaped to help prevent numbness with the groove down the center and some may find it is comfortable enough but as with all bike seats this definitely won’t be for everyone.

You can try standing on the pedals every 10 minutes to give some relief while you try to get used to the seat. You can also try padded bike shorts and/or a gel seat cover. The bike seat size is 7 ins by 10.5 ins and 1.5 ins.

If that doesn’t work you can swap out the seat for another more comfortable bike seat.

Handlebars The handlebars are covered for a good comfortable grip and prevent slipping when hands are sweaty. They are shaped to give a good variety of positions. The inner handlebar is used for the tablet but the outer are curved to provide an alternative and for the aero as well as having “horns” to grip when up out of the saddle.

Noise This is a quiet bike that can be used at anytime of the day and night and not disturb others. Some people have used it in the same room as others including children are sleeping without disturbing but may still wake up a light sleeping spouse.

In a separate room they shouldn’t hear you at all depending how deep you are breathing.

If you want to watch TV you don’t have to turn it up high to hear it.

It can be used in an apartment even an upstairs one – there is none of the pounding you have with a treadmill. Although you may want to put on an exercise mat to stop any vibration from being transmitted through the ceiling.

Dirt The bike won’t add too much to your cleaning chores. It is important to wipe it down with a damp cloth regularly to keep it looking and working at its’ best. The biggest cleaning concern is likely to be sweat which is corrosive and the main reason for the wipe
down. You may also want an exercise mat to protect your floor.


You can’t fold the bike up when you’ve finished for storing out the way.

It needs an area of 49 ins by 22 ins when not being used – it has a good finish so won’t look bad in your home. It can be stored alongside a wall or under the stairs but is probably too big for a closet.

It comes with 2 small transport wheels at the front of the bike to help you when you want to move the bike around. It is too heavy to carry for most, it weighs 111.3 lbs.

You tip the bike on to the wheels which is easy to do as much of the weight is at the front with the flywheel. You can then move the bike to where you want to go. Going round corners and avoiding furniture does take a little care but you don’t have to worry about the weight too much.

The wheels work best on hard surfaces. If you have thick carpet you may find the wheels stick and you have to drag it rather than wheel. Also, on wood floors you may just want to check that the wheels don’t leave scratches.


The Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike comes mostly assembled with the frame, cranks, drive and flywheel put together.

This leaves the customer to add the pedals, stabilizer bars, support posts, seat, handlebars, dumbbell holder, water bottle holder and console to the bike.

It has a shipping weight of 125.9 lbs. Moving it from outside to where you want to complete the assembly can be one of the biggest challenges.

It is recommended that two people work together to assemble the bike. Thist is important in particular when adding the stabilizer bars to hold it steady. It is possible for one person to do this but they need to be careful handling the weight.

The instructions and tools are included with the bike. Sunny like to start the instructions with a diagram and list of all parts but that level of detail is not required for completing the bike.

Care is needed when adding the pedals to make sure the pedals are attached to the correct size as the left pedal has a reverse thread (as is normal for bikes) and needs to be screwed in reverse (lefty-tighty/counter clockwise) otherwise the thread may be stripped and cause issue with pedals loosening as you workout.

Most people can complete the job in less than an hour and it is easier than most IKEA furniture is to assemble.

Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike Console

I know there are people out there who don’t care to see their numbers as they workout. I’m not one of those and find them motivational and a help to keep me on track.

The screen and numbers displayed are a reasonable size to see while you exercise. The console can track speed, cadence, distance, calories, time and pulse when sensors are gripped.

The default setting is miles but this can be changed to kilometers if you prefer.

The screen is split into 4 sections:

At the top of the display is usrf for race and targets functionality with illuminated bars for target and arrows.
For cadence it has a range between 15 – 120. The pre-set value is 60. Or you can set for race mode where it can be set for time and distance where it is set in 10 minutes or 4 miles

The next section down is where you can monitor speed or cadence, below that is distance or calories and below that is time and pulse.

The functions are:

Speed is measure from 0 to 99.9 mph or kph. You can also see average and max speed when stopped
Cadence is RPM measure up to 999 (that is good going (to say the least) if you get anywhere near the top measure) and you can also see average and max when stopped
Distance – up to 999.9 miles or km. You can set a target distance rather than just have it accumulate
Calories accumulate up to 9999 or you can set a target
Time up to 99:59 or you can set a target time
Pulse your current heart rate

There are 3 buttons below the screen for changing the mode, setting and re-setting.

It doesn’t come with Bluetooth to work with or upload to an App. If you want to record workouts for tracking purposes you need to do this manually.

The monitor requires 2 AAA batteries (included with the bike) and are placed in the back of it which is easy to do.

It doesn’t monitor your resistance levels.

You can track you pulse to monitor how hard you are working by grabbing both sensors in the handlebars.

These can help you keep a check from time to time but you are unlikely to be using them constantly as you likely want to change your hand positions as you move through your workout.

If you are wanting to use the bike with Peloton the cadence measure is useful to help you to follow the instructions. You’ll need to estimate your resistance level. It may be a little tricky if you are using heart rate zone classes as you need to grip the pulse sensors and you may want to do this using a heart rate strap and App.


The weight and dimensions of the bike are

Height 46.5 ins
Width 22 ins
Length 49 ins

Flywheel Weight 40 lbs
Max User Weight 300 lbs
Bike Weight 111.3 lbs


There are 3 additional accessories that this bike come with as standard:

Water bottle holder This is on the right hand fork at the top of the flywheel. You do need to stretch a little for bottle when you want to take on refreshment. It won’t fit an oversized bottle and you may find if it is too long you hit it with your knee.

Dumbbells Holder These are in a handy position at the front of the bike on the left hand fork. They can handle up to 10 lbs dumbbells. Being at the front puts them easy reach for when you want to add some upper body and core exercise to your workout. You do need to bend down a little to reach them but is easier than trying to reach them from behind or from the floor. You should also not bang your knee on the handlebars when out of the saddle.

Media Device Holder This sits between the handlebars ahead of the console. If you are following along to workout classes it puts it close to your workout data on your console – you can keep a check on both easily, or watch TV or movies.

You lay your tablet or phone on the holder, so there is no restriction on depth. The bike doesn’t move around so your device should be safe and not be falling on the floor.


  • Can be adjusted to fit people with an inseam between 29 ins and 39.5 ins
  • Includes dumbbell holders up to 10 lbs each
  • Easy to assemble
  • Adjustable to fit range of body types and heights
  • Includes console
  • Transport wheels
  • Magnetic resistance
  • Belt drive
  • Low maintenance
  • Very quiet bike
  • Dual pedals
  • Seat and pedals can be swapped out


  • Doesn’t come with Bluetooth
  • Handlebars only 2 way adjustable
  • Need to track workout numbers manually
  • Uses hand pulse sensors to track heart rate
  • No guard for magnetic resistance and flywheel

Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike Consumer Ratings

Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike ReviewOn Sunny’s site the reviews are very favourable but there is little feedback on other sites currently.

They like that it is quiet and has a solid build with no wobbling. The ride feel is smooth too. Some weren’t a fan of the seat and one person out of 54 had a trouble with their pedal clicking (although this may have been more common when first released).

Sunny bikes on a whole are well regarded by customers for their ability to provide a good platform for workouts and to be long lasting.

The feedback on Sunny’s own site appears to support the expectation that this is another good bike.


This is a mid range priced bike and it is less than a 1/3rd of the price of the Peloton. However, it doesn’t come with all the extras like dumbbells and resistance levels measured.

It includes dual pedals, a monitor, tablet holder and dumbbell holders in the price along with the magnetic resistance and belt drive.

When I checked the price at Amazon it included free delivery on eligible order although there were issues with availability.

Check availablity and current price
Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike

Review Summary

The bike comes with some good extras as well as a heavy duty frame, 40 lbs flywheel, magnetic resistance and belt drive for a quiet and solid basis for low impact cardio workouts.

This makes it ideal for beginners and those more experienced. The dual pedals also help here too with the choice of footwear and you can change to spinning shoes when or if you want..

The addition of the dumbbell holder makes it much easier to exercise the upper body too especailly when following a workout class that includes this.

Including a console gives you the measurements you may want for your workouts and following along to classes without having to add sensors or computers afterwards.

It doesn’t have Bluetooth so it isn’t compatible with Apps for recording but you can follow along to fitness Apps (Peloton Digital) you just won’t see your measures.

It provides a good basis for the benefits from indoor cycling workouts with some nice enhancements too.

3 comments for “Sunny Health & Fitness SF-B1851 Synergy Pro Magnetic Indoor Cycling Bike Review

  1. December 10, 2020 at 3:33 pm

    What is the q-factor? The distance between pedals? Narrow? wide ?

    • Paul
      December 10, 2020 at 6:26 pm

      Sorry, I don’t know the measurement. I’ve asked Sunny to let me know.

      • Paul
        December 16, 2020 at 4:34 pm

        Sunny have replied and stated it is 200 mm (7.87 inches) – it is on the wide side which can add stress to the joints but this can depend on hip width etc.

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