Rockrider E-ST 900 Review: Affordable Mid-drive eMTB from Decathlon


Easy E-Biking - Decathlon Rockrider E ST900 e-bike, helping to make electric biking practical and fun
Photo courtesy of Decathlon

Just after its first electrically-assisted mountain bike, Rockrider e-ST 500, Decathlon is back in the game with its first mid-engine mountain electric bike, Rockrider e-ST 900. It is an exclusive model intended for a cyclist to ride smoothly on mountain treks.

Presentation of Rockrider E-ST 900 mountain electric bike 

Electrically assisted mountain bikes have always been a hot topic because they are becoming more affordable, but still quite expensive. Their prices often exceed the 3000 euros mark. This very thing leaves a sweet spot for the large distributors in the market, including Decathlon. 

However, the French brand, Decathlon has changed the game by introducing its first mid-engine mountain bike, for only around 2000 euros. It has a central motor and gives twice torque as compared to Decathlon’s previous model, Rockrider e-ST 500, which costs around 1300 euros. 

Read also: Front, mid or rear motor, which one to choose? – in this article. And Rockrider E-ST500 V2 Review: a solid starter eMTB – in this article.

The E-ST 900 integrates a powerful 250-Watts Brose motor with an impressive torque deliverance of 90 Nm. Other than that, it is coupled with a 504-watts battery to provide great performance and sufficient autonomy for excursions and steep hills on the mountain treks. 

Moreover, the bike is fitted with 27.5-inch wide tires along with a RockShox Judy suspension fork at the front. Fitted with a Shimano Deore transmission, this bike aims to provide above-average performance, for all the mountain lover bikers out there. 

It has a reasonable and aggressively fair price, given it includes high-quality equipment. Electric mountain bikes of other brands come with an excessively higher price than Decathlon’s e-ST 900, even though they have the same equipment. 

Read also: How much does a mountain e-bike cost? – in this article.

Easy E-Biking - Decathlon Rockrider E ST900 e-bike, helping to make electric biking practical and fun
Photo courtesy of Decathlon

Comfort and ergonomics 

With its wide tires and battery located just beside and over the downtube, it is impossible to hide its electrical character. 

It comes in a sober color made of gray, white, and black. The Brose motor is visible even though it is in the protective case located along the same axis as the battery. 

Decathlon finds pride in integrating high-quality components in its eMTB. However, its frame does not have the desired finishes that every cyclist is likely to want. 

The crankcase, junction rubber, and the seat are made of plastic and barely provide a basic all-in-one deal. In general, dirt from the mountain environment can easily house inside the frame, making maintenance and cleaning more difficult. 

The cyclist won’t be able to skip maintenance and cleaning for a long time. To deep-clean the bike, it will be necessary to dismantle some of its parts.

This is nothing shocking at this level of price range as we did not expect the battery to be fully integrated or the seat to have the finest quality. These not the top choices were precisely the part of the price factor. Other brands’ eMTBs are already 50% or even 100% more expensive. So, we must say this bike overall has a good package in its 2000 euros. 

E ST900 geometry and riding position

Coming to the integration level, Decathlon managed to keep the geometry of the e-bike quite close to the muscular frame. The horizontal tube and the curved shrouds give a little more muscular character to the e-bike. Also, the dimensions of the frame also contribute to its muscular character. 

The bases of the bike are kept short (probably 449 mm), thanks to the motor orientation, which is upwards. However, it limits the wheelbase of the cycle and a bit prevents better handling. The depth of the frame is quite suitable for all sizes (379 mm to 445 mm). 

Easy E-Biking - Decathlon Rockrider E ST900 e-bike, helping to make electric biking practical and fun
Photo courtesy of Decathlon

The riding position of the e-bike is designed for mountain treks. It is also possible to adjust the stem angle to raise handlebars (5 steps of 7.5 mm: from 0 to 30 mm). The five-step system enables the cyclist to adopt a pilot position, which we prefer on the mountain treks. 

Coming to comfort, we appreciate the large 2.8-inch Taipan Koloss 27.5-inch plus tires. They deliver good shock absorption and compensate for rear shock absorption. 

Weight, seat, and suspension 

The bike is rather heavy, around 22.1 kg, and its rigid aluminum frame seemed relevant to us since an eMTB needs a good grip to ensure traction on the mountain treks. It would have been really good if the frame was created using tubeless aluminum, mounted on 36 mm rims. 

The B’Twin Ergofit Evo saddle provides adequate cushioning for a mountain bike since it has a thick foam. However, the manufacturer could have opted for a suspended seat post to provide more comfort. 

Decathlon has put a standard original rod seat, but we would have appreciated a telescopic seat post as it helps if the rider alternates between descents and ascents. 

You can count on RockShox Judy suspension fork at the front wheel side to absorb impacts. With its rebound adjustment, 120 mm travel, and a blocking tee, this entry-level fork is right for non-busy mountain treks. 

On-board computer, lights, and reflectors

Even though e-ST 900 is a mountain electric bike, Decathlon has provided lights, bell, and wheel reflectors to comply with the legislation on bicycle sales. Entry-level plastic pedals are also provided in the whole package. But, due to wear and tear, the rider will soon be changing them. 

Easy E-Biking - Decathlon Rockrider E ST900 e-bike, helping to make electric biking practical and fun
Photo courtesy of Decathlon

Now, coming to the engine control: the e-bike has an all-in-one board computer attached next to the left handlebar. It lights up by pressing and holding the top-most button on the computer. Menu navigation on the computer is rather easy and is done by a small 4-way clickable joystick. 

The home screen displays the instantaneous speed while indicating the selected range (in the form of sticks) and the assistance mode as well. The estimate of the range of kilometers is easy to find as it scrolls on the screen every time you exert power on the pedals. 

Unfortunately, this information cannot be displayed at the same time as the instantaneous speed and the level of assistance.

Also, you got to stay or make your way back to the main menu to see which mode is activated. This design is not practical, to be honest, but it comes with a small bonus: a micro USB socket on the right side to charge your smartphone or link a GPS system. 

Motor and on-the-road performance

The key element of the 250-watts Bosch engine is that its torque deliverance is 90 Nm. As compared to other engines (those that deliver 75 to 80 Nm), it is quite good. 

However, the official website of Brose says (link to the website) that the very same engine delivers 70 Nm at maximum assistance of 320%. This is not an error from the side of the Decathlon as the Brose could have provided a customized version of the engine for the e-bike.

One of the facts about mountain electric bikes is that raw power is not everything. Manufacturers are not bound by engine standards and display the results that best suit them. It is rather impossible to know the intensity of power being delivered to the wheels, based on the technical sheet provided by the manufacturer. 

Despite having 2.8 inches wide tires, with a powered-off engine, the e-bike is rolling on the roads smoothly and without much noise. 

Read also: Do electric bikes make noise? Are e-bikes loud? – in this article.

It does not take long, even for a beginner to turn on electrical assistance. The first level of electric assistance adds 40% of the power. Thus, by activating the first level, it is possible to compensate for the e-bike’s heavy weight.

Read also: How much do e-bikes weigh? – in this article. Or how to select electric assistance levels on an e-bike? – in this article.

Easy E-Biking - Decathlon Rockrider E ST900 e-bike, helping to make electric biking practical and fun
Photo courtesy of Decathlon

Electric assistance modes

The assistance modes are changed simply by pressing the arrow keys on the left of the on-board computer. It would have been good if the arrow keys were flatter and a little wider. Otherwise, it could be necessary to press the arrow keys by the tip of the thumb. It seems like a not very natural operation as compared to just pressing down the buttons. 

The second electric assistance mode, known as the ECO, power levels quickly reaches +80% of electric assistance. Even though it is enough to go up rather steep slops most of the time, it shows its limits as soon as the slopes become steeper. It would then be helpful to switch to mode 3, which is called “Standard”. This mode gives enough power to climb steeper hills at the assistance of more than 160%. 

Read also: Can e-bike help go up steep hills? – in this article.

The Standard mode, at full power, offers the most versatility. All that remains is to juggle the 10 speeds to maintain a good pedaling frequency (cadence). The combination of a 34-tooth mono chainring and a cassette with 10 sprockets (11-42 teeth) is sufficient to ride at a good speed without forcing too much on the climbs. 

Chain, derailer, and breaks

The e-ST 900 model also benefits from a chain guide, from Chain Flow technology to minimize the risk of derailment. 

Despite these safeguards and the use of a reinforced chain, it would make sense to still avoid changing gears too wildly while crushing the pedals, to respect the mechanics.

Read also: How to use gears on an electric bike, mechanic and electric? – in this article.

Easy E-Biking - Decathlon Rockrider E ST900 e-bike, helping to make electric biking practical and fun
Photo courtesy of Decathlon

The Shimano Deore M6000 Shadow + derailleur nevertheless allows rapid gear changes. We appreciate that Decathlon did not make an economical choice in this case. 

Rockrider e-ST 900 is rather intended for rides in the high mountains. This is also why this model has the fourth electric mode, called “Boost”. This mode delivers electric assistance of +320%. 

While climbing mountains, the engine works at full speed, at a torque deliverance of 90 Nm. It is sometimes too much, so, it is better to stay on the back to stick the wheel on the ground and prevent it from slipping. 

Decathlon could have taken the effort to better configure the electric assistance, or could have taken advantage of integrated intelligent assistance modes on motors such as Bosch Performance CX Line engines, for example. 

When braking, you can count on Tektro TKD32 hydraulic disc brakes. With their 180 mm discs at the front and rear and their double piston calipers, they provide enough power to sharp stop the bike on mountain trails. 

Rockrider E-ST 900 autonomy

On all e-bikes, the electrical assistance varies, whether it is an urban city e-bike or a mountain e-bike. To determine how far one can ride on a full charge, the elevation is one of the main factors. However, the condition of the terrain (muddy, dry, etc.), tire pressure, the way of driving, the frequency of pedaling, and the weight of the mountain biker are some major factors to consider as well.

In Standard mode, one could expect to travel around 40-50 km on relatively flat terrain, if using this assistance level most of the time. 

If you travel on hilly trails, including steep climbs and use the Boost mode from time to time, an estimated distance would be around 30 km.

Easy E-Biking - Decathlon Rockrider E ST900 e-bike, helping to make electric biking practical and fun
Photo courtesy of Decathlon

Coming to the battery’s charging time, it takes 3 hours to recharge, which is quite reasonable for a 14 Ah 36 V battery. The charging is done directly via a battery connector. It is accessible even when the battery is integrated on the bike. 

It is nevertheless possible to remove the battery (to charge it separately) with a simple turn of the key by pushing it to the left of the bike.  

To indicate the charging, a charge level indicator with 5 LEDs is present on the top of the battery. Decathlon guarantees its battery for 2 years or 500 charges/discharge cycles. The bike has a Samsung SDI cell battery which, according to Decathlon, must retain around 70% of its capacity at the end of the warranty. 

Rockrider E ST900 datasheet

Material Aluminum 6061
Engine Brose T, 250 watts, 90 Nm
Number of speeds 10
Autonomy announced50 km
Battery weightNC
Drums 504-watts, 36 volts, 14 Ah
Wheels 27.5 inches
Luggage rack/anti-theft kit/tool kitNo/no/no
Bike weight22.1 kgs

Pros of Rockrider E ST900

  • Powerful, responsive mid-drive motor.
  • Comfort and good grip due to 27.5-inch wide tires.
  • Shimano Deore transmission.
  • Frame geometry not much influenced by the electric motor.

Cons of Rockrider E ST900

  • Poor integration of central motor and battery.
  • Control of electrical assistance modes not easy to handle while riding.

Final remarks about Rockrider E ST900

The Rockrider E-ST 900 is a well-balanced electrically-assisted mountain bike that benefits from a good equipment pack. Overall, it would be a good hiking companion. 

Whether you want to take advantage of the e-bike’s motorization to ride further and higher, or simply want to follow a group of more experienced mountain bikers, Decathlon Rockrider E-ST900 is a sane and safe choice. 

Its Brose central motor, in any case, offers enough power and performance to fully enjoy the benefits of electric assistance on mountain treks. Overall, it is a good, well-equipped mountain bike at a reasonable price of 1999 euros.

Here is a quick video, introducing Rockrider E ST900 on various terrains:

Recent Content