adidas C-21x Indoor Cycle Review

adidas are one of the most recognised sports brands in the world. This behemoth of a manufacturer is a global sports giant that’s got reach into just about every area of sports, and cardio equipment is no exception. We took a close up look at the adidas C-21x bike to see how the current adidas cardio catalogue compares to what else is out there. Here’s what we found…

Like all exercise bikes these days the C-21x comes flat packed and needs to be put together before you can start. Assembly here is very much what we’ve come to expect from most indoor cycles these days and we managed to complete the build in comfortably less than an hour, so a good start.

Once built, the C-21x looks very sleek but it also looks sturdy and we can confirm this isn’t a trick of the light. This is a very well specced and built indoor bike. There’s a 16 kg / 35 lb rear-drive flywheel that’s been designed to duplicate the feeling of riding an outdoor bike by storing energy and maintaining momentum. This results in an impressively smooth cycling action all the way through the entire cycle, and at any resistance level produces consistent cadence. It feels very good indeed and is a stand-out feature of this bike. Another impressive aspect of the C-21x is the riding position you can get. The race-style saddle adjusts vertically and horizontally, the handlebars adjust vertically too and all of this is done via quick-release adjustment mechanisms that are as easy to use as any we’ve come across. The handlebars are another element of this bike that is designed to help you find the ideal riding position. They’re fully adjustable with armrests and support multiple riding positions which really does help you to get comfortable. Not only do these things mean that it’s easy to get an ergonomically correct riding position regardless of your stature (which is vital on a bike like this) it also means that if you have more than one person in your household regularly using the bike, it’s unlikely that you’ll get frustrated having to change the riding position to suit you every time you want to workout. The mechanisms all feel slick and solid making this task as easy as it can be, reinforcing the impression of a very well designed and built bike.

We’ve seen a lot of different models of this type of bike but unlike a lot of other indoor cycles which either require you to press a button on a computer to scroll through the resistance levels or to turn a knob to manually adjust the resistance, the C-21x has a shifting paddle that is located front and centre that allows you to select any one of the 8 available levels nigh-on instantly. This makes it incredibly easy to jump up or down multiple levels of resistance quickly and is perfect for HIIT training given the ease and speed with which it’s possible to alter the resistance. It’s ultimately a very simple idea and it works beautifully (which, along with the excellent ergonomics, goes to show that adidas has put a good level of thought into this bike) and makes this setup ideally suited to both sprints and long, flat endurance sessions. The ride that the C-21x delivers is genuinely impressive as a result of the high-quality components used in the construction and clear thinking employed in the design here and this makes this indoor cycle suitable for a huge range of riders of all skill levels.

Away from the ergonomic and mechanical functions, the C-21x’s cycle computer delivers live performance metrics including speed, time, distance, calories, pulse and RPM. This model comes supplied with a chest strap so you can monitor your heart rate accurately which is handy given there are 4 workout modes on the computer consisting of 3 manual target modes for time, distance and calories and a target heart rate mode. Using a target heart rate mode on any bike is something that we firmly believe only works properly and safely when using a chest belt and it’s nice to see adidas include one here with the bike. The computer itself is easy to use and can more or less be used without the need to read through a pile of instructions. Simple but effective, which, in a lot of ways, sums up this model. The computer itself is powered by the rider as this is a self-generating bike so as one starts to turn the pedals, the red LED circle on the main body of the bike lights up and the computer stirs to life. The energy generated by the rider charges the console batteries (not included) meaning that it’s not necessary to give any consideration to where a power socket is in the relation to the bike making it much easier to place it in a location that really works. In addition, a tablet/smartphone holder has been integrated into the design of the console so that you can easily mount a smart device and watch video content during your workout.

Other features include a set of leg-levellers so you can get the bike sitting absolutely flat even if the floor’s a bit uneven and a water bottle holder which is something often missed on a bike like this. For peace of mind, the C-21x is covered by a 2-year manufacturer warranty.

Best Price

Currently available for £599.00 from

Review Summary - In Brief

With a 16kg flywheel, a 150kg max user weight,  heavy-duty components, quick adjustment mechanisms and high-quality construction, this is a slick and very well built bike that is quite capable of challenging any rider. The speed and ease with which it's possible to alter the resistance make it ideally suited to HIIT training and other high-intensity workouts while that hefty well-balanced flywheel delivers a high level of performance and road bike simulation that makes endurance sessions feel as comfortable as they're ever likely to get. This bike may not have interactive features, but it does everything you'd want an indoor bike to do and does it really, really well. Easy to recommend

adidas C-21x Specifications

    • 16kg (35lbs) flywheel
    • 8 levels of manual resistance with quick-shift paddle
    • LCD display
    • Feedback: Time, speed, distance, calories, RPM, pulse
    • Programmes: 4 (3 manual target modes (time, distance, calories), target HR mode)
    • Hear rate measurement via Bluetooth Smart wireless receiver (chest strap included)
    • Handlebars: Adjustable multi-position handlebar
    • Seat: Sprint saddle with horizontal and vertical adjustment (seat height: 77cm – 93cm (30″ – 37″))
    • Pedals: Jendel spin pedals with toe cages and adjustable straps
    • Transportation wheels
    • Conveniences: Integrated tablet/smartphone holder, dual water bottle holder, leg levellers, Ultra Series red LED lighting
    • Dimensions in use (L x W x H): 151cm (59”) x 57cm (22”) x 137cm (54”)
    • Max. User Weight: 150kg (331lbs)
    • Product Weight: 56kg (123lbs)
    • Power: Self-powered; console requires 7 AA batteries (not included)
    • Warranty: 2 years

adidas C-21x Indoor Cycle - Console / Display Unit

adidas C-21x Indoor Cycle - User Reviews

The Pros

  • Easy to get a great riding position
  • Fast resistance changes
  • High quality construction
  • Chest belt included

The Cons

  • The racing saddle won't suit everyone, but we're being picky here given the target audience of this bike
adidas C-21x Indoor Cycle Reviewer Ratings


Appearance - 9
Smoothness - 9.5
Comfort - 9
Programmes - 7
Ease Of Use - 10
Warranty - 8.5
Value for Money - 9
Best Price

Currently available for £599.00 from

Also see our Exercise Bike Comparison Table

Whilst every effort is made to give you accurate information we cannot guarantee the technical specification. Models change on a regular basis and may differ slightly from the above review. We recommend you contact the retailer if you have a question regarding technical data. Please read our Legal Disclaimer

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