In this comprehensive Sunny SF-B1709 vs Keiser M3i comparison I put them up against each other in detail to show how they really do stack up against one another.
They have a similar look with the rear flywheel (out of the sweat
zone) and a number of the features appear alike too but their a differences.
One of the most obvious is the price difference with their being a wide margin between the two bikes.
They both do look good – I like the wheel at the back and they both have features that add to the overall indoor cycling and spinning experience.
Before getting into the detailed comparison here is a quick review of each exercise bike:
Keiser M3i Indoor Cycle
This bike is used in gyms across the country. It is a premium commercial bike with a price to match but it seems to live up to the expectations for the most part.
It is also used by many in the home.
It has a light flywheel at the back of the bike but provides a smooth and consistent pedaling motion due to how the belt drive is set up.
It has magnetic resistance that provides a wide range from easy to hard controlled by a lever by the handlebars.
The level of resistance you are at is displayed on the console at the front of the bike along with power and cadence and more.
This bike is rated highly by most customers having one of the best overall ratings of any indoor cycle.
Sunny Health & Fitness SF-B1709 Magnetic Rear Belt Drive Indoor Cycling Bike
The Sunny SF-B1709 (for short) is a more affordably priced bike but has more than most bikes in Sunny Health & Fitness range of exercise bike. It does come with more benefits.
You have the “light” flywheel at the rear of the bike, the belt drive, magnetic resistance, 4 way adjustable seat and handlebars, and a basic console.
It won’t interact with Apps but you can follow along to App workouts or online videos, although it doesn’t have a tablet holder, so you may need to watch through your TV or by a mount separately.
It provides a smooth pedaling motion for a natural low impact indoor cycling workout.
Most customers overall are positive about this indoor cycling bike.
How They Match Up To One Another
There is a table below that has the Keiser M3i vs Sunny SF-B1709 match up line by line, with the specifications.
Before that here is a comparison of the exercise bike’s features with explanations of the differences.
Both use magnetic resistance to increase and decrease the intensity needed to turn pedals over using a lever rather than a tension knob. You move it up and down to increase/decrease the level of resistance. They are in slightly different location with the Keiser M3i having it by the bottom of the handlebars and the Sunny SF-B1709 lower down the handlebar support. The M3i positioning is closer to hand.
As mentioned below with the console the M3i has 24 levels/settings and this can be seen on the console.
The Sunny SF-B1709 has 13 settings and you have to determine the level you are at by the feel of how hard it is to pedal or by counting clicks or from the position of the lever. It is similar to many other indoor cycling bikes and is something most people get used to.
Personally, I like the M3i with the display of level but it isn’t too much of a hardship to use an indoor bike without this.
The other difference in the working of the resistance is that the SF-B1709 clicks through to set levels giving you distinct settings where as the M3i is on a continuous and incremental process which is like most other indoor cycles – you can set resistance to setting you want rather than a distinct setting.
It moves through the levels on a smooth basis without clicking into place like you have with the SF-B1709.
People using the SF-B1709 do find the transition between the levels to be smooth and easy to manage. I assume it helps to control resistance but this is different to most indoor cycling bikes and is more like an upright bike type of resistance adjustment.
This is an area where there are a good number of differences. The Sunny SF-B1709 has a basic console that includes the measure of cadence which can help in following along to classes. It also measures calories, speed, time, distance, cadence and pulse rate. The pulse is measured when you grip the hand sensors on the handlebars only.
The Keiser M3i is the winner here. It provides you with power, resistance level as well as cadence, distance, calories and pulse. The screen is well designed and is backlit to help with seeing it when the light isn’t the best.
To measure your pulse you need to wear a heart rate strap that does need to be bought separately, sometimes it is available as part of a bundle.
I prefer a strap myself – I’m not a fan of the hand pulse sensors even though they are included with the bike. I find if I want to monitor my heart rate I want it constant not just when I’m gripping the appropriate place on the handlebars and the strap is usually more reliable too.
And there is Bluetooth too …
Bluetooth and Apps
The Keiser M3i does have both bluetooth and its’ own App as well as some compatibility with third party Apps. It allows you to upload your data to display on your phone ot tablet as you workout or for recording progress over time.
There is additional compatibility with convertor (needed to be bought separately) to the Peloton Digital App and you can see your cadence, but you won’t feature on the leader board.
You have to buy the convertor separately and with you can also connect to connect to the Zwift App.
The SF-B1709 has no connectivity. You can use it with Apps workout classes as you would with a video you just don’t get your stats to show on the App. Nor can you upload workout data to fitness apps automatically. To have some compatibility with Apps you can add cadence sensors like the Wahoo with works with Peloton amongst others, you can also add heart rate with a compatible strap and speed (although a little more involved).
Seat and Handlebars Adjustment
Both bikes have 4 way adjustment on handlebars and seat- up/down and front back to get the most effective and comfortable fit.
The Keiser M3i has a quicker set up with the adjustment handles rather than knobs and you can tighten the up/down adjustments where you want them.
The Sunny SF-B1709 vertical adjustments have pre-set holes where you insert the holding pin restricting in a small way where you can set the height of the handlebars and seat.
For most the difference in time to adjust won’t impact much on getting
started with your workout or class.
The height range of the bikes has the Keiser with a wider range from 4ft 10 ins to 7 ft 0 ins and the Sunny being most suited for those between 5 ft 0ins and 6 ft 3ins based on customer experience.
The Sunny has a wider seat at 8 ins by 10.5 ins by 2 ins and some may find it more comfortable than the narrower Keiser seat. But this is down to personal preference.
Some will find the seat of each bike not to their liking. This seems to be a general rule for all indoor cycle seats. Comfort on the sit bones is very much a personal thing. I’ve yet to come across one that everyone likes.
Fortunately, if you can’t tolerate the seat from perseverance or
padded bike shorts or gel seat cover, you can change out the seat for an alternative one. Both indoor bikes’ seats can be replaced by other bike seats as they have standard fittings.
One of the most striking similarities is the flywheel at the back of the bike out of the way of sweat.
Also, both exercise bikes have a light flywheel compared to most other indoor cycling bikes.
The Sunny SF-B1709 has a slightly lighter one at 7.36 lbs vs Keiser M3i flywheel weighing in at 8 lbs.
Despite the light weight flywheel of both bikes when compared against the common use of heavy flywheels (around 40 lbs) both bikes provide a smooth and constant pedaling motion.
This is due to the design of the drive resulting in the flywheel turning faster to give the inertia to help keep the pedals turning through the entire pedal cycle at all levels of resistance helping to stop an up/down motion that adds more impact to the cycling.
Both have a fixed gear set up. You aren’t able to coast or freewheel.
When the flywheel is turning so are the pedals. To stop you can use
the resistance lever to use as a brake or gently push back on the pedals.
Water Bottle Holder Positioning
This may not be one of the biggest concerns as they both have a place to keep water close at hand for when you need a drink.
The Keiser M3i sits at the bottom of the frame where you need to bend down to reach it – it just rests there rather than having to be inserted into a holder. You may find you drop sweat on it too.
The other concern is that depending on how you get on the bike you may kick it or catch your foot, if you step through the bike to get on and off.
With the Sunny SF-B1709 the holder is at the front between the handlebars – you need to place the bottle into the holder. You don’t need to bend down for it. It is easy to take the bottle out and put it back in.
However, I think overall I prefer the bottle holder on the Keiser but that is really down to personal preference but either will get the job done.
The Keiser M3i has a position on the handlebars that you can place your tablet or Ipad to have the workout classes and data close at hand or for entertainment. The Sunny SF-B1709 doesn’t have this option, however, there are tablet mounts that can be bought separately.
There are only a few inches difference and probably only make a difference when storing or when buying an exercise mat to protect floor and bike rather than when using the bike.
The wider bike is the Keiser at 26 inches and Sunny at 23.6 inches.
The SF-B1709 is the longer bike at 53.2 inches with the M3i measuring 49 inches.
Both bikes are lighter than many other indoor cycling bikes but I don’t think you would call them light.
They both have small transport wheels at the front of the bike to make it easier to move it around. You tip the indoor cycling bikes forward on to the transport wheel to take the weight of the bike and leave you to navigate them to where you want it to go.
The M3i weight is 85 lbs and the Sunny SF-B1709 is a little heavier at 89.3 lbs.
Both bikes require some assembly with the Sunny SF-B1709 being the simpler of the two. It also comes with all the tools needed to complete the job.
For the Keiser M3i the tools need to be bought separately with a torque wrench recommended which is something many people won’t have in their toolbox. You can buy a tool set separately (direct from Keiser) and sometimes this set can be included in bundle deals that have been run from time to time.
Both can be put together at home and most find that both don’t involve anything too difficult but the Sunny bike assembly is the easier. The flywheel is attached but with the Keiser it has to be installed by the customer.
Both bikes come with dual pedals where there are toe cages on one side and SPD clips on the other.
There have been some concerns over the quality of the pedals with the
Sunny SF-B1709 expressed by a handful of customers. However, most appear happy that the pedals meet their requirements but the pedals aren’t top of the line and you may want to swap them out as you become more experienced.
That is something that can be done with both of these indoor bikes – you can change the pedals with other ones that have a 9/16 thread.
Both frames are solid with very little to no wobbling giving a stable base for your workout in and out of the saddle. The Keiser M3i has an aluminum frame and the SF-B1709 a steel frame. SF-B1709 is coated to helps prevent rust to the steel frame.
There can be a big difference in price between the bikes with the Keiser M3i being a commercial quality bike designed to take the wear and tear of use by many users day in day out.
When buying the Keiser for home use some customers look to buy refurbished bikes used in a gym setting and can get a good bike at a much reduced price. It is important to study the market to help you get the second hand bike at the right price. They do look used but they can perform very well and for a good period of time too.
The Sunny SF-B1709 is rated for home use. It won’t stand up to being used in a commercial setting but should be fine in a home setting.
The Sunny SF-B1709 also doesn’t have the same level of console functionality or magnetic resistance and can’t connect to any Apps.
Here is the side by side list for a full comparison of the two exercise bikes:
|Feature||Keiser M3i||Sunny SF-B1709|
|Flywheel Weight||8 lbs||7.36 llb|
|Pedals||Dual Toe cages/SPD||Dual Toe cages/SPD|
|Bike Weight||92 lbs||89.3 lbs|
|Max User Weight||300 lbs||300 lbs|
|Min User Height||4 ft 10 ins||5 ft 0 Ins|
|Max User Height||7 ft 0 ins||6ft 3 ins|
|Dimensions||Height 45 ins|
Width 26 ins
Length 49 ins
|Height: 54.3 ins
Width: 23.6 ins
Length: 53.2 ins
|Q Factor||197 mm||XXXX mm|
|Accessories with Bike||Water Bottle Holder|
|Water Bottle Holder|
|Accessories buy separately||Exercise Mat|
Convertor (to work with Zwfit etc)
|Assembly Required||Yes -Some|
(Tools not provided)
|Yes - Some
Which One to Get?
The Keiser M3i is a very good indoor cycling bike and one of the best available for home use. It’s not perfect (I’d like to see more console functionality come as standard). You get a bike that is reliable and durable that gives a very good natural indoor cycling experience at any level of experience and intensity.
The quality and longevity are supported that it is seen as good buy second hand even when it has been used at a gym – albeit that it may have been refurbished. They are sought after items.
The biggest concern is the price. If it is within your price range you are unlikely to be disappointed with the bike’s quality and performance.
If you don’t want to spend in that range then the Sunny SF-B1709 Magnetic Rear Belt Drive Indoor Cycling Bike can be a good choice to get most of the same cardio benefits at a more affordable price.
It would be great to know your thoughts on these indoor cycles and which one you think is right for you. Or if you have decided on one or the other – which one did you opt for? Is there something I missed?