By Robbie Ferri, Cyclist, Personal Trainer, and Group Exercise Instructor.
If you have been looking into Spinning Bikes or Exercise Bikes, you would have come across the name Sunny. They make incredible bikes, and the Sunny SF 1851 Synergy Pro is an excellent example of this. The SF B1851 Synergy Pro is one of their most popular models, but is it worth it? In this article, we will put it up against the other popular indoor cycle from Sunny (SF B1805) and one of the most popular indoor cycles, in general, the Schwinn IC4.
Quick Comparison Table
Bike | Sunny SF B1851 | Schwinn IC4 | Sunny SF B1805 |
---|---|---|---|
Resistance System | Magnetic | Magnetic | Magnetic |
Flywheel | 40lbs | 40lbs | 44lbs |
Drive | Belt | Belt | Belt |
Warranty | Frame: 10 years & Mechanical Parts : 180 days | Frame: 10 years & Mechanical Parts : 3 years | Frame: 10 years & Mechanical Parts : 180 days |
Weight Capacity | 300lbs | 330lbs | 300lbs |
Size | 42”x10” | 49”x22” | 42”x10” |
Detailed Review
Includes a 40lb inertia-ready flywheel belt drive mechanism to provide a smooth & quiet ride. Its magnetic resistance provides quick, easy, & reliable resistance changes.
- Use SAVE10 coupon code on Sunny Official Site for 10% OFF!
- Free Cadence Sensor to Sync with the SunnyFit App! Applied to your Cart!
Specifications
- 40 lb flywheel
- 300 lb weight capacity
- Magnetic tension system
- Adjustable inseam: Min 29 in / Max 39.5 in
- Caged/SPD compatible pedals
- Warranty: 3 year structural frame 180 days other parts and components
- Product dimensions: 49L x 22W x 46.5H
The Sunny SF B1851 Synergy Pro is a beautiful

The layback seat design looks excellent, and it has a classy look to it with oversized tubing. It’s a sturdy and robust
Flywheel and Drive Chain
It’s a belt drive system, and this has enormous advantages compared to other systems on the market. Using a belt gives you a better connection to the
The flywheel is a perfect weight and sits at 40lbs. The flywheel is the big wheel at the front that you must drive around. Having a heavy flywheel makes the
It has a magnetic resistance system which is very impressive. Magnetic resistance systems are what they call frictionless. A Frictionless system doesn’t require a brake pad like many spin bikes do. This will use magnetic force to create resistance on the flywheel. To increase the resistance, all you have to do is turn the dial in front of you while on the
It is a fantastic system and again removes the need for maintenance. The
Accessories
The Sunny SF B1851 Synergy Pro is full of great accessories, and I feel they have done well here to add to the user experience. The



Alongside this great monitor, you also have a heart rate monitor on the handlebars. Where you see the silver metal pads on the bar, hold this, and it will give you a heart rate reading. This is great to see how hard you are working or to ensure you are not working with too much intensity on those longer sessions.
The next is the pedals. Instead of running ordinary toe clips, the Sunny SF 1851 Synergy Pro has toe clips on one side and SPD clip ins. These are the pedals where you can clip in and use special spinning shoes. Having these pedals will save you money and time when upgrading your footwear on the



You also have a bottle cage on the fork, which I thought was a lovely touch as it keeps your drink out the way, but easy to get to while riding. On the other side of the fork, you also have a holder for dumbbells. The handlebars have a mount in the center. This is a device monitor, so you can use a tablet and spin to an application or even watch a film if you can keep up the pace till the end.
Adjustability
The

Assembly and Set up
It’s not a challenging
The Sunny SF B1851 Synergy Pro vs. The Sunny SF B1805 Indoor bike
Priced usually under $600, this model offers users an experience often reserved for higher-priced options. This quiet belt-driven model includes a heavier front flywheel weighing in at 44 pounds.
A great
They are both great bikes, but the B1851 does come out on top, in my opinion.
The Sunny SF B1851 vs. The Schwinn IC4
Comes equipped with Bluetooth connectivity, allowing you to link to several apps such as Peloton® and Zwift®. The Schwinn really does offer excellent quality at a very affordable price.
Let’s come away from Sunny bikes, and let’s compare the B1851 to another branded
The Schwinn IC4 is an excellent bike and looks great too. Many people commonly use the Schwinn IC4 as an alternative to a Peloton because of its connectivity via Bluetooth. Although it looks great, the Sunny B1851, in my opinion, looks a bit more solid and has a more attractive exterior to it. Internally, as with the other bikes, they are very similar because they are both magnetic and belt drive.
The monitor on the Sunny does give similar data fields to the Schwinn, but the Sunny has an inbuilt Heart Rate monitor. Unfortunately, with the Schwinn, this is separate and has to be worn. The Schwinn monitor does supply Bluetooth connections and also a power function. The power function is only an estimate, but it can still measure your progress. Overall the Schwinn has a better monitor.
I feel the Sunny has a better look to it and is a solid, simple
Alternatives to the Sunny SF B1851 Synergy Pro
Sunny Evolution Pro 2
The 40 lb flywheel provides momentum while you ride on this low impact cycling machine. The smooth and silent belt-drive mechanism guarantees your cycle exercise will be quiet, particularly in shared spaces.
The Sunny Evolution Pro 2 is an excellent
Sunny SF B1879 Synergy
This belt-driven bike includes a 30-pound flywheel and performance monitor. It offers pulse-sensing handlebars.
- Use SAVE10 coupon code on Sunny Official Site for 10% OFF!
- Free Cadence Sensor to Sync with the SunnyFit App! Applied to your Cart!
If your budget doesn’t quite stretch to the Sunny SF B1851, then this is the
Sunny SF B1877
In addition to the quiet ride, this model includes a battery-operated performance monitor that displays cadence, speed, distance, calories, time, and heart rate.
Another great alternative to the B1851 is the Sunny SF B1877. It has a lesser monitor and the same technology as the Sunny SF B1851 and is well worth looking into.
How does the Sunny SF 1851 review by others?
The Sunny SF 1851 Synergy Pro gets excellent reviews online. We get some people who don’t take to it too well, but most people love it. One common issue is that if you are below 5ft 3”, you might find it harder to get the proper position, besides that, glowing reviews.
Warranty
Sunny doesn’t offer an excellent return policy. They offer 180 days on parts and labor and 3 years on the frame. This is ok, but the normal on other spinning bikes is about a year. The Schwinn has a better warranty, and I hope Sunny will change this in the future.
Conclusion

Includes a 40lb inertia-ready flywheel belt drive mechanism to provide a smooth & quiet ride. Its magnetic resistance provides quick, easy, & reliable resistance changes.
- Use SAVE10 coupon code on Sunny Official Site for 10% OFF!
- Free Cadence Sensor to Sync with the SunnyFit App! Applied to your Cart!
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