The Nautilus U614 (pictured left) and the Nautilus U616 (shown below to the right) are moderately priced upright exercise bikes made by respected fitness industry giant, Nautilus.
Both come with a wide variety of workouts programs, multiple resistance levels, and a range of valuable features and accessories.
Utilizing eddy current resistance, the bikes are equipped with high-speed, high-inertia perimeter weighted flywheels that deliver very smooth and almost silent rides.
Both have an easy-to-read dual-track LCD monitor for viewing workout stats.
With either model, you will be able to export your data to NautilusConnect, the Nautilus Trainer app, or MyFitnessPal.
Handy accessories include Acoustic Chambered Speakers, an MP3 port, and a charging USB port.
Both models come with a heart rate monitor, a 3-speed fan, a conveniently located water bottle holder, and a media shelf you can use to hold an electronic device or book.
This Nautilus U614 and Nautilus U616 comparison review looks at the specs of both models, their features, similarities, and differences.
Table of Contents
Nautilus U614 & Nautilus U616 Specs
Dimensions – Both bikes measure 41 1/2″ x 23″ x 12 3/4″
Weight – They weigh 73 lbs
User weight capacity – The user weight limit for both models is 300 pounds
Nautilus U614 & Nautilus U616 Key Features Compared
In this section of our Nautilus U614 and Nautilus U616 comparison, we will look at their features and variations. 
The Nautilus U616 Upright Bike is Nautilus’ top-of-the-line upright exercise bike.
It is more expensive than the Nautilus U614, and it comes with some additional features. The most important of these to some will be its more comprehensive range of programs and resistance levels.
How do the Programs Compare?
The U614 has 22 workout programs. These include 1 Quickstart, 9 Profile, and 2 User Profiles.
There are also 8 Heart Rate Controlled programs (4 Beginner and 4 Advanced), and 2 Fitness Tests (1 Beginner and 1 Advanced).
The U616 has 29 workout programs. These include 1 Quickstart, 12 Profile, and 4 User Profiles.
There are also 9 Heart Rate Controlled programs (4 Beginner and 5 Advanced), 2 Fitness Tests (1 Beginner and 1 Advanced) and 1 Recovery Test.
How do the Resistance Levels Compare?
The U616 has 25 levels, while the U614 has 20. Both have 1 Quickstart Resistance Program and 10 Quick Keys for instant selection.
The 10 levels you can access by pressing one button on the U616 are levels 1, 3, 5, 7, 9, 12, 15, 18, 21, and 25.
The 10 levels accessible this way on the U614 are levels 1, 3, 5, 7, 9, 12, 14, 16, 18, and 20.
Transitioning between the levels is smooth, and the difference between each is relatively subtle.
The lowest levels offer relatively easy workouts, while the higher levels are challenging, particularly on the U616.
If you are new to exercise or very out-of-shape, start with level 1, which provides virtually no 
resistance and progress to the higher level as you become fitter.
When using one a pre-set workout programs the resistance level automatically changes to keep you in that range. To override this, press the button showing the level you want to implement.
25 levels of resistance, and even 20, is more than most exercise bikes come with and beyond adequate for most people.
If you are already quite fit or plan on taking your workouts to the next level, the Nautilus U616 will be the better option. Its top levels of resistance will challenge all but the fittest athlete. ]
How do the Seats & Pedals Compare?
The seat of the Nautilus U616 is larger than the seat of the Nautilus U614 Upright Bike.
The seats of both models can be raised or lowered to suit the height of the user. The seat of the U616 also adjusts fore and aft.
Seat adjustments are quick and easy to implement. A seat post system allows the seat on both models to be exchanged for another seat if desired.
The Nautilus U616 has larger pedals than the Nautilus U614.
Are there any Other Differences?
Both bikes have a dual display monitor, but only the U616’s is backlit. 
The U616 is Bluetooth enabled, while the U614 is not.
Both models have contact heart rate monitoring. The U616 is also telemetry enabled to accommodate a heart-rate chest strap.
What is the Assembly Time?
Assembly time for these bikes is approximately 60 to 90 minutes.
While not hard to do, a second person will make the job easier. The tools you need will be in the box.
Are there any Negatives?
Nautilus U614 Negatives:
The seat of the Nautilus U614 Upright Exercise Bike doesn’t adjust horizontally. While more comfortable than the seat of many exercise bikes, some purchasers have said it’s uncomfortable.
Comfort perception typically varies between individuals, so not exclusively to this model. Placing a towel on the seat or buying a gel seat cover will help to remedy this.
The bike will need to be plugged into an electrical outlet to utilize the program and resistance level functions.
Not having a backlight, the monitor can be difficult to read in dim lighting.
Nautilus U616 Negatives:
Not everyone will find the seat of the Nautilus U616 Upright Exercise Bike comfortable.
This is a common problem with exercise bikes, especially when using them for extended workouts. Placing a folded towel over the seat or buying a suitable bicycle seat cover will largely fix the issue.
To use the bike, you will have to plug it in. The power cord is on the short side, so you might need to use an extension cord or place it close to an electrical outlet.
Which Model Should You Choose?
The Nautilus U614 and the Nautilus U616 are great exercise bikes, and you won’t go wrong with either. 
Both bikes are excellent value for money. The model you choose to buy will largely depend on how fit you are to start and how far you want to grow your fitness.
If you are a new or intermediate exerciser who wants to improve their fitness to a certain degree, then maintain it, the Nautilus U 614 will be perfect.
If you’re looking for a greater challenge, with its additional resistance levels and workouts programs, the U616 will probably be more appealing.
Able to store the details of four people, the U 616 will suit you the best if the bike will be used by more than two people in your household.
The U 614 would be great for two people who want to share the bike and store their stats.
As well as being height adjustable, the seat of the Nautilus U 616 is also fore and aft adjustable. This makes for a truly customizable fit.
To read more upright bike reviews, click this link.
