Sportstech SX400 Review: A 22kg Flywheel Spin Bike With App Control

The Sportstech SX400 is a mid-priced indoor cycling bike from the German brand Sportstech, aimed at home riders who want a heavy, stable, quiet spin bike without paying premium smart-bike money. Its headline features are a chunky 22kg flywheel for a road-like pedal feel, a quiet belt drive, arm supports, and app connectivity through the Sportstech and Kinomap platforms. The honest verdict is that the SX400 is a well-built, capable manual spin bike that punches above the budget class, provided you understand that you adjust the resistance yourself rather than having an app do it for you.

What you are paying for over a cheap indoor bike is the ride quality and the build. The weighty flywheel and belt drive combine to give a smooth, momentum-rich stroke that feels closer to riding outdoors, and the wide adjustability means a range of body sizes can get a proper fit. It is not a fully connected smart bike, but as a solid platform for structured indoor cycling at home it is a sensible mid-market choice.

Who it is for

The SX400 suits home riders who want a proper spin bike for regular, structured cardio and are happy to control the resistance manually while an app handles the workout and tracking. Indoor cycling is a genuinely effective way to improve your fitness and health: a study of an indoor cycling programme found improvements in cardiometabolic markers, including a rise in protective HDL cholesterol and a drop in inflammatory markers (indoor cycling and cardiometabolic factors). If you want fully automatic, app-controlled resistance and a big built-in screen, a connected smart exercise bike is a better fit. If you only want occasional light cardio, a cheaper spin bike will do the job.

Build and ride feel

This is where the SX400 justifies its price over budget bikes. The frame is heavy and planted, so it stays stable when you push hard or climb out of the saddle, and the 22kg flywheel is the star of the show. That extra mass carries momentum through each pedal stroke, smoothing out the dead spots and giving the ride a satisfying, road-like weight rather than the light, spinny feel of cheaper machines. The belt drive keeps it all quiet, which matters in a home where you might ride early or late.

Fit is well handled. The seat adjusts up, down, forward and back, and the handlebars adjust too, so riders of different heights can dial in a comfortable, efficient position. The pedals typically take both a cage for trainers and an SPD clip for cycling shoes, which is a nice touch for anyone who rides outdoors as well. As with all friction-based spin bikes, the resistance pad needs occasional adjustment and eventual replacement over the years, which is normal upkeep rather than a fault.

App, workouts and console

The SX400's connectivity is a real plus at this price. Pairing it with the Sportstech app or Kinomap unlocks video routes that respond to your effort, structured workouts and multiplayer rides, which does a lot to keep indoor sessions interesting. The important thing to understand is the type of connectivity: the app tracks your ride and guides the session, but you change the resistance yourself using the bike's dial. It is app-connected, not app-controlled. For many riders that is perfectly fine, and it keeps the price well below a true smart bike, but it is the key distinction to grasp before buying.

The built-in console is deliberately basic, covering the core numbers while leaving the richer experience to your own device on the tablet holder. That is a sensible way to keep costs down and avoid paying for a fixed screen that ages quickly, though buyers wanting a large integrated display should look elsewhere.

Performance and value

In use, the SX400 delivers exactly what a good manual spin bike should: a smooth, heavy, quiet ride you can push as hard as you like. The stepless friction resistance goes from an easy spin to a genuinely tough grind, so it covers everything from steady endurance rides to hard intervals and standing climbs. It is stable and reassuring under load, which is where cheaper bikes often fall down.

On value, it sits in a sensible spot. It costs more than entry-level indoor bikes, but the flywheel weight, build quality, adjustability and app support explain the difference, and it undercuts fully connected smart bikes by a wide margin. If you want a dependable, road-feeling spin bike for regular home training and do not need automatic resistance, it is easy to recommend. To see how it compares with the wider market, read our best spin bike UK guide, and if you are still deciding between machines, our look at whether exercise bikes are good for cardio is a useful companion.