Rockrider E-ST 900 Electric Mountain Bike Review

Decathlon keeps on adding new electric (mountain) bikes to their collection. The new Rockrider E-ST 900 electric mountain bike is one of these ebikes. The E-ST 900 might be the most impressive ebike in their lineup yet. Not only has it the highest specs, but it also comes at an affordable price that you can expect from Decathlon. If you are looking for an ebike with high-quality components but don’t want to spend the premium of other brands, this is the one for you! In this review, I will tell you all the things to like about this stunning Decathlon E ST-900 electric mountain bike!

Rockrider E-ST 900 review

Electric Motor

Let’s start with the most impressive part of this E-ST 900 ebike: the electric motor. The electric motor used by Decathlon is manufactured by Brose. Brose is a large automotive part manufacturer that also produces top-quality electric motors for ebikes. The Brose electric motors are a textbook example of great German engineering. The motors therefore also compete with the best in class ebike motors from Bosch and Shimano.

Output power

The motor used is the Brose “Drive T” model. It’s a mid-drive motor with an internal belt drive for extra smooth and quiet transmission. The motor has a built-in torque-sensing pedal assist, 70NM of torque, and 250W op power. The actual peak power will be higher in boost mode (300-400W), but the legal listed power is 250W. All these features make this motor truly outstanding, especially when you consider that the bike only costs around 2000 euros (1700 pounds)!

Brose T specification

The torque of 70NM is the most important specification of this motor. The torque of an ebike is the force at which the motor can rotate its axle. High torque is desirable since it will enable you to climb any hill effortlessly. This Brose motor has a torque of 70NM which is truly amazing for a 250W motor. Most ebikes, especially hub motor ebikes, will only produce around 40NM of torque. So 70NM is almost double this!

Torque-sening pedal assist
Brose motor exploded view

The pedal assist is of the torque-sensing kind. This means that the ST-900 ebike will measure the force you exert on the pedals. It will assist you with a certain amount of power dependent on the force you exert on the pedals and dependent on which assist mode you are in. This will result in the most natural-feeling electric assistance, the electric motor will become part of your body. Torque-sensing pedal assist is often found on high-end ebikes, so having it at this price point is amazing as well.


Decathlon also didn’t cut costs on the drivetrain. Decathlon went for a high-quality Shimano Deore M6000 1 x 10 groupset. This includes an M6000 trigger shifter and an excellent Deore Shadow+ rear derailleur.

Having a good drivetrain is especially important for mid-drive ebikes since there will be a lot of added force on it by the electric motor. If you have a weak drivetrain in addition to a powerful mid-drive motor, you can possibly break chains and wear out cassette gears really quickly. Luckily this isn’t the case here because of the excellent Shimano gear.

Decathlon even went the extra mile by installing an excellent KMC E10 turbo chain. This chain is specially designed to handle the high force that electric mid-drive motors can output. This great drivetrain shows that Decathlon really put in the effort to make this E-ST 900 electric mountain bike as reliable as possible, which is great.

Display and range

The E-ST 900 has a small but convenient-to-use display. I like that they didn’t go with a big middle-mounted display with separate buttons. Combining the buttons and display into one unit makes it really sturdy and discrete.

The display shows all the relevant information like: speed, assist level, battery percentage, remaining range, trip distance, and more. With the buttons you can set the bike into 4 different assist levels:

Range and assist levels
Assist levelNamePowerRange (Estimate)
Assist level 0Off+0%
Assist level 1Economy+40%130 kilometers, 80 miles
Assist level 2Economy ++80%105 kilometers, 65 miles
Assist level 3Standard+160%70 kilometers, 45 miles
Assist level 4Boost+320%30 kilometers, 20 miles

These 4 assist levels give you great control over the amount of power you want to use. In the economy mode, you can expect a range of about 130 kilometers (80 miles). In the Boost mode, you can expect a range of about 30 kilometers (20 miles). This range can be considered excellent, especially when you consider that the motor outputs a lot of power in boost mode.


The battery of the E-ST 900 is made out of high-quality Samsung SDI 18650 lithium-ion cells. Having brand-name cells inside an ebike battery is always important for reliability, performance, and safety. Decathlon went with Samsung 18650 cells, which is a great choice.

The battery has a great capacity of 504Wh (36V, 14AH), this is a more than excellent size battery for an ebike at this price point. Some electric mountain bikes have smaller batteries to lower the overall weight. I think Decathlon made an excellent decision not to make this design choice. The advantage of having more range is much more useful for most people. Especially if you consider that most people will not go hardcore mountain biking, but just ride casually. In that case, the big battery will really come in handy.

The battery is also is removable which makes it convenient if you want to charge the battery inside. The charger that is included is a 36V, 4A fast charger. Charging at 4A is about as fast as the theoretical maximum charging rate. So it’s nice that Decathlon included the fastest charger possible. Charging from 0 to 80% will take about 3 hours with this charger.


The frame is made out of strong 6061 hydroformed aluminum tubes. The frame is covered by Decathlon’s lifetime warranty for mountain bike frames. So you probably don’t have to worry about it falling apart. The welds on the frame are neat and the paint quality is nice as well.

The battery is integrated into the frame and can be slid in easily. Once the battery is in, the battery can be locked down. Preventing someone from stealing your battery.

The frame comes in two colors: grey with silver accents and grey width orange accents. I personally really like the look of the grey with silver accents frame. it gives the E-ST 900 a stealth and premium look.


The E-ST 900 has Tektro TKD32 hydraulic brakes installed in combination with 180mm discs. This combination gives the ebike plenty of stopping power. I, however, don’t recommend you to use this ebike for extreme downhill mountain biking. For this purpose, the brakes just aren’t quite sufficient. Therefore I would say the only part of the E-ST 900 that could be improved is the brakes. But for most riders, these brakes will still be absolutely fine.


The E-ST 900 uses a RockShox Judy front fork. This is a hydraulic/pneumatic suspension with 120mm of travel, adjustability, and a lockout feature. This front fork isn’t the best that RockShox has to offer, but it definitely suffices. Comparable ebikes at this price point often have a lot more basic front forks. So for its price, this RockShox Judy is excellent.

The suspension allows for comfortable light trail riding or serious off-roading. Both can be done without a problem.


The first thing you probably notice about the E-ST 900 is its massive tires. The E-ST 900 comes with 27.5 inches by 2.8 inch wide tires. These are absolutely massive tires that offer a lot of off-road grip. They also offer a good level of protection against punctures due to their massive size.

The tires are installed on 36mm wide Sunringle DUOC 40 27.5″ wheels. These wheels are off the thru-axle style that provides great stability and a precision fit. They are also easy to remove if you need to do any maintenance.

E-ST 900 only for mountain bikers?

So, is the E-ST 900 only suitable for mountain bikers? I would say definitely not. The E-ST 900 is a great ebike for daily commuting as well. You will have an ebike with high-quality components, a powerful motor, great range, and a nice pedal assist. This makes it perfect for daily commutes as well. You will also get the added benefits of a mountain bike, like great front suspension and massive tires for amazing grip. You could also add a luggage carrier and mudguards to make it truly suitable for daily driving. Therefore I would say this E-ST 900 is suitable for casual riders, commuters, and semi-professional mountain bikers.

So whether you are looking for a great off-roading machine or a nicely riding daily commuter, the E-ST 900 will not disappoint. If you are a really professional mountain biker you mind come across its limits. But for most casual/semi-professional mountain bikers this ebike will definitely deliver.

Buy Rockrider E-ST 900 Electric Mountain Bike @Decathlon


Decathlon has built an absolutely amazing e-bike for only 2000 euros. The E-ST 900 features the highest quality components at a stunning price point. There just aren’t any other brands that can compete with this ebike at the moment.

The German-engineered Brose T motor in addition to the big Samsung battery makes this ebike ride truly amazing. The other components of this ebike are also absolutely outstanding at this price point. The E-ST 900 just ticks all the boxes and I can’t think of something really bad about it.

If you want a high-quality electric mountain bike to use for serious off-roading, casual trail riding, or for daily commuting, this ebike is perfect for you. For 2000 euros there will simply not be a better option. I really can’t recommend this ebike enough!

In case you liked this bike, you might also like the E-ST 520. It’s the cheaper alternative to the E-ST 900 of Decathlon. It shares a lot of the same amazing components but at a lower price point. Definitely check out the review to find out if this ebike might suit your needs even better.

If you have any questions, want to start a discussion, or need some support, please use the comment section below. I will respond to you within 24 hours.


  1. I bought one a few weeks ago. Now they are out of stock and probably for a long time or forever. So I’m proud to own this beast. One major issue though : after driving only 150 km (on flat terrain) my chain broke ! Luckily enough they fixed it immediately at the local Decathlon store. My bike still makes weird sounds though. Another issue : the reach (kilometers left) is not very accurate so you might encounter some unfortunate ‘surprises’ when you think you can still drive 10 km and the power stops. When shifting from eco to turbo or vice versa, the remaining reach also stays the same, which is not correct and misleading

    • Btw I only use it to drive to work, not on heavy tracks. Average speed is higher than on my Batavus because of the faster acceleration. When driving uphill (a bridge) you can feel the power, like if somebody pushes you uphill.

  2. Is there possibility to change tire settings (size) in the computer? I have better wheels and tires and I want to switch, but it means that I’ll change diameter. To have correct speed values I should change these settings.
    What about if after 2 years I would like to change battery? Is decathlon supporting parts after warranty and we will be able to buy new ones? Ebike without battery could be problem in the future.

    • Hi,

      To my knowledge, and by looking at the manual, you can’t change the wheel diameter. If you however only change the tires, and maintain the rims, you should be fine. The difference in diameter other tires will have is slim and it won’t effect your speed reading all that much. If you want to change the rim diameter as well, the difference will be bigger though. I however don’t see a reason why you would want to do this.

      Decathlon often offers replacement parts even after the warranty period. Decathlon has a great reputation when it comes to this. So I shouldn’t be to worried about this. Even if they won’t supply it, you can always do a battery revision on your old battery. But I am also confident that you can still buy replacement batteries after 2+ years from now.

    • Hi, i have the est 900 and have bought a replacement battery, i have had no difficulties getting spares/replacements for my ebike, although items do go in and out of stock currently (post brexit)

  3. Hello Giel,
    Good review mate, I’ve decided to take the plunge and go for the E900.
    If the tyres are too noisy on the road then I’m sure I can live with that for the price.
    Looks a very good deal in comparison to what is offered elsewhere.
    Cheers Jon

    • Hi John,

      Nice! You won’t regret it! You can ofcourse always get smaller width tires fitted, with less profile. This will decrease noise dramatically. The rims are however quite wide as well, so you can’t fit really skinny tires, but you can definitely fit some smaller ones. I am sure your local bike shop could fix this for you, if this would be needed.

      • Hello. I have a problem. my e 900st connected speedbox and it works well.
        But when we take off the speedbox system on display tells us that we can pass 30 Km.
        When the limit is reached, it switches off but the batteryd still have power…
        Service has no answer why it happened.

        thanks for help

        • Hi Vlad,

          Could you clarify? You connected a speedbox? Is this an extra device to increase the maximum speed on the bike?

  4. Bit the bullet and bought a Rockrider EST 520. I was a bit apprehensive buying without seeing one but am really happy I’m 6’2 stocky build and went for a XL frame and on the minimum for most settings so it a generous size. Everything seems well put together and gears and engine work well together, I find the 3 speed controller is fine and three speeds more than adequate and bike cruises up all hills with ease. One thing worth mentioning is on the first day when I switched motor on by holding on button for 2 seconds I had an error come up showing error 31 this was not in the manual or on the internet emailed decathlon and they did not know what it was I rang the Oxford store and they contacted Bros motors and found that error 31 one was just that I had held the start button for too long which was a relief because when you have an error you are a bit wary of using the bike so hopefully that helps somebody. I think it’s a good bike and for my circumstances suits me better than the 900 as I felt the wheels were too large for me on the 900 and I will probably put some type of road tyre on as the the standard tyres are fine off road but a bit noisy on road.

    • Hi Ian,

      Thanks a lot for sharing your thoughts! I think the error 31 story can really help others as well, thanks! I am also glad you are happy with the bike, it really is a great bike at this price point.

  5. Hi Giel, I recently purchased this bike. So far so good, brakes could be better, drive train and motor very quiet and positive. I would like to change the tyres to a hybrid version for commuting. The tyres supplied are fine but I am unsure what will fit the rims? Great reviews. Thanks

    • Hi Mike,

      I am glad you like the bike! The rims installed are 35C (35mm) wide. This are quite wide rims and will only fit certain tires.

      Here you can find a chart that shows which tires you could fit to a 35C wide rim:

      Please look at this chart carefully. You should find some road tires that will apply with this chart. Because they should be quite big, they can be hard to find. But it should be possible.

  6. Thanks for your reply. As I’ll be only using the bike for mainly road use with the occasional off-road I’m having a rethink and looking at the St 520 as well . I was wondering on the 520 if a later stage you could upgrade the controller from the 3-speed to the 4 speed and swap the battery perhaps to the 500. With regards to the est900 as they are 27.5+ wheels is it easy to get tires for that size for road use I’m not quite so bulky. sorry for all the questions just trying to weigh things up before I take the plunge. Cheers Ian

    • Hi Ian,

      The E-ST 520 will indeed also be a great option. Maybe even better because its price is lower. If you don’t need the off-road capability, the 520 is an excellent choice as well.

      Controller upgrades are not possible between the bikes. It isn’t necessary though. They are physically the same, only a software difference. Having 3 or 4 power mods doesn’t really matter. Both ebikes have a good selection of power modes. 4 modes definitely isn’t absolutely necessary, 3 modes will work just fine.

      The batteries can be interchanged between the 520 and 900. But I don’t think you can purchase a separate 500wh battery to use on the 520. But in Theory you can swap them around.

      Finding road tires for the 27.5 inch + rim can indeed be difficult. The 520 has a smaller rim width. Fitting road tires to these rims will be easy. So if you absolutely want road tires, the 520 can be easily equipped with road tires.

  7. Cheers and thanks for your speedy reply, which makes total sense and was along the lines I was thinking but good to hear it from someone who more in the know than me. A shame as no Decathlon stores close to me and really liked the look of their bike which had alot of quality features. Thanks very much for your assistance Ian

    • Cheers again and appreciate your comments which make sense, looked on decathlon site and and under the st900 parts you can get a 500 battery and on the ST5 20 parts you can get a a 400 battery so worth knowing for the future. The only thing I’m not fully sure about on the 520 is the gears are a micro something advent which I have not heard of before but I think at the moment the 520 ticks all the box thanks so much for your help Ian

  8. If you have any questions about this ebike, please leave a comment below. I will try to answer your question within 24 hours. If you own this ebike yourself and you want to share your experience, please do so as well.

    • Hi thanks for the review on this bike it all sounds pretty positive. I was set on getting an Cube Acid Hybrid 400 but due to shortages in my size 6’2″ it’s all on hold. Then I saw this and wonder if a) the decathlon 900 would be ok for road use as 90% of the time be on the road with an occasional short cut across fields. B) don’t know alot about the Brose engine and live in darkest Wales with Halfords being the nearest bike repair/service so would the Bosch engine on the Cube bike be easier to get repairs done and how easy is it to get the Brose engines repaired and what is the reliability like as it the engine which a concern to me as not heard as much on them as the Bosch…sorry for all the questions but nice to hear from someone in the know….Cheers Ian

      • Hi Ian,

        I think the E-ST 900 will handle road use as well as the cube acid hybrid. To make it more road friendly, you of course can always change the tires to more suitable road tires. This will result in less tire noise and higher range when using it mainly on the roads. As of reliability of Brose vs Bosch motors they tend to be equally reliable. The Bosch motors however are generally easier to repair. Because Bosch is the bigger brand, service will also be a bit better.

        But the advantage of buying a bike from Decathlon, is that you get their support as well. If something will go wrong with the motor, you will need to contact Decathlon. Decathlon has excellent customer support and will handle any possible issues with Brose. So as long as you have a Decathlon in your area, I won’t worry about this.

        If you only have a generic bike service place in you area, you will probably have more chance to get fixes for Bosch than for Brose.

        So my advice: Both Brose and Bosch motors are equally reliable and probably won’t fail on you for a long time. If you have a Decathlon in your area -> The E-ST 900 is an excellent choice. If you only have local no-brand bike service shops and the closest Decathlon is really far away, you are probably better of with an ebike with a Bosch motor. Because Bosch is the better know brand, it’s more likely that they can fix it at local repair shops.

        Hope this helped. If you still have any questions, please respond to this comment.

    • Hi . Purchased an e- st900 and want to connect my android mobile to the display unit. I can’t work out what connector I need to connect to the display. Please can you help ? Thanks in advance.

      • Hi Sean,

        According to the manual it has a micro usb port on the display. Therefore you will need to have a micro usb plug on one end and your phone plug at the other end.

        This is probably a cable that you would have to buy, since it isn’t a standard cable. If you buy one though, you will be able to charge your phone from the display.

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