27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow


This electric mountain bike has been designed and developed by us to best suit mountain-bike rides on hilly and rolling terrain.

With the E-ST 520 electric mountain bike, you can tackle any climb. With the help of its built-in motor (70 Nm torque), even the most difficult of hills will be manageable.

Color: Pale grey / Fluo lime yellow
Size: size guide


Product benefits


Head for the summit powered by a 250W motor with 70Nm torque


Ride an average of 2.5 hours at a sporty pace thanks to the 420Wh battery.

Smooth pedalling

The built-in motor automatically assists you when needed. Perfect for MTBing.

Cycling comfort

Enjoy: raised position, 120 mm suspension, wide tyres, hammock Ergofit saddle.

Directional control

Control your trajectory: hydraulic fork and brakes, tyres and a wide handlebar.

Technical information

Which is the right size?

Several sizes available:
S: between 1.50m and 1.64m
M: between 1.65 m and 1.74 m
L: between 1.75 m and 1.84 m
XL: between 1.85 m and 2.00 m

If you are between 2 sizes:
Choose the smaller size for easier steering (easier to handle) and comfort (straighter back).
Choose the larger size for easier pedalling with a more stretched-out position (position more suited to performance).


You have to pedal to go forward!
The electric assistance boosts your pedalling by 320%, helping you ride over obstacles.
You'll get to enjoy longer MTB rides.
The motor stops providing electrical assistance when you stop pedalling.
The walking mode offsets the mountain bike's weight when you need to walk your bike.


Our team of mountain bike enthusiasts created this E-ST 520 electric mountain bike entirely at our B'Twin Village in Lille, France.
We designed and tested the E-ST 520 MTB by involving MTB riders at every stage of the project.


The frame of the Rockrider E-ST 520 electric MTB is made of 6061 aluminium with hydroformed tubes. Why? The battery sits snugly on the frame to improve the robustness of this electric mountain bike.
The forged aluminium parts make it compatible with the new 27.5"+ tyre format (wider than the 27.5") in the rear, while remaining easy to manoeuvre. We've kept a frame geometry with short bases for easier steering.


The BROSE T Aluminium central motor is specially designed for mountain biking:
- 70 Nm torque to handle large obstacles and steep gradients
- metal housing for maximum durability
- belt for an ultra-quiet motor
- sealed bearings to hold up to tough environments while mountain biking


Our battery is equipped with battery cells from LG or Samsung, (LGC-MG1 or SDI), which are known for their high level of reliability and safety.
Our battery supplier sources its minerals responsibly and sustainably, and is part of the "Responsible Minerals Initiative".


Our Rockrider mountain bike team has designed a battery that locks in place with a simple lever. Child's play!
This locking system prevents the battery vibrating when riding on rough terrain.
There is also a lock in case you want to stop your battery getting stolen. For example, if you park your bike in the street.


A discreet LCD control screen. It is located just to the side of your left grip, so you can choose between the 3 assistance modes without letting go of the handlebars: (Deactivated), Economy, Standard, and Boost.
You'll also find a host of useful information:
-Current speed
-Average speed
-Maximum speed
-Distance covered
-Total distance
-Battery level
-Remaining battery range (in km)
-Active assistance mode


Mode 0 - Deactivated
The battery is not used.

Mode 1 - Economy +60%:
Extend your rides while conserving battery life. Ideal when you want a little push on small gradients.

Mode 2 - Standard +120%:
This is the most versatile mode. Climb any slope without getting too tired and without using too much power.

Mode 3 - Boost +320%


Ride over obstacles (roots, pebbles, stones, etc.) easily thanks to the Rockshox XC30 hydraulic fork with 120 mm of travel.
This fork has:
- A coil spring for maximum sensitivity and reliability - a lockout and preload adjustment for better control, depending on the terrain


The E-ST520 electric bike is equipped with a single chainring and ChainFlow 3D anti-slip technology to prevent the chain from derailing.
A single shifter on the right handlebar makes it easy to shift between the 9 speeds.

In detail:
-Chainflow & Anti-derailment single chainring with 34 teeth
-Microshift Advent 9-speed rear derailleur with long cage
-Microshift Advent right shifter
-Microshift H093 9-speed cassette (11 to 42 teeth)
-KMC E9 Sport electric bike specific chain


These wheels were specially designed for this mountain bike:
- 23 mm rims (width between brackets), 28 spokes at the front and 32 spokes at the rear, for greater durability and good grip with wide tyres (up to 2.5").
- BOOST thru rear axle (12x148) for greater durability
- Aluminium hubs with sealed bearings

- TUBELESS READY rims: you will need TUBELESS tyres, specific Presta valves, and puncture sealant.


In order for you to feel safe on any terrain, and for traction suited to your motor, the E-ST520 electric MTB is equipped with Hutchinson Cougar 27.5" tyres with a 2.4" cross-section. Our test riders particularly liked these tyres for their grip on the ground. Mounted on wide rims, these tyres provide great grip, traction, and comfort on any terrain.


Regardless of the conditions you ride in (dry/wet/muddy), the hydraulic Tektro TKD88 disc brakes at the front and rear provide powerful and progressive braking. Oversized 180mm diameter discs provide even more power.


The adjustable stem brings the E-ST 520 controls to your hands. The all-aluminium Rockrider stem is 70 mm (size S), 80 mm (size M/L), or 90 mm (size XL) and can be raised to 5 adjustment intervals: + 0mm, + 7.5mm, + 15mm, + 22.5mm, + 30mm.
In detail:
- 720mm oversize Rockrider Sport aluminium handlebar
- Rockrider Sport "soft touch" ergonomic grips for good grip and a comfortable feel.


Since your mountain bike rides will get longer and longer, it is important to have a suitable seat. Our teams have designed the exclusive Rockrider Ergofit Evo saddle. It fits all hip sizes and has a curved shape that is particularly good for sport trail rides.

The 31.6 mm aluminium seat post ensures compatibility with most adjustable and suspended seat posts on the market.

Platform pedals

The bike comes with 520 GRIP MTB platform pedals (ref. 8487130) with a wider pedalling surface and more pronounced dots for better grip on the pedal.However, if you are looking for improved performance when pedalling and better control of the bike when cycling, we recommend replacing them with clipless pedals with platforms or wide aluminium platform pedals.


Your E-ST520 mountain bike is fitted with a bell, lights, wheel reflectors and pedals.

The frame is compatible with:
- front and rear mudguards
- stand
- bottle cage (on the horizontal tube)
- saddle pouch
- rear pannier rack (fixed onto the seat stays or special mounts for wide bikes, 148 mm gap for the rear wheel & 2.8" fat tire)
- child seat


Tip no.1
When mountain biking, there is always the risk of a fall: don't forget to wear a helmet.

Tip no. 2
A puncture could happen at any time, so always remember to take a repair kit and a 6 mm Allen key for removing your wheels.

Tip no.3
If you don't want to stop to drink, bring water in a bottle or water bladder to access it while riding.


To ensure components last longer, we recommend a maximum load of 120 kg (rider and MTB included).

Care advice

Leave your battery on the bike when washing using a hose. This will protect the connectors from rusting.


Lifetime (frame, stem, handlebar). Availability of spare parts: 2 years.Guaranteed for 500 charges.


22.5 kg
Weight without pedals.

Product concept & technology

Product Composition

Frame 100% Aluminium 6061


Store it in a warm, dry place away from corrosive products and salty air. Never store with the battery flat, and remember to recharge it at least once every six months.

User Directions

Don't forget to remove the battery to handle the chain.


Our engineers always have real riders test all our products in real conditions. These tests round out our lab tests and let us validate all our products before they hit store shelves.


To have more informations about this product, consult the notice


27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow
27.5 Inch Electric Mountain Bike E-ST 520 - Grey/Yellow



Q:How to assemble your bike?

A: Everything you need to know about making sure your bike is comfortable, secure and ready to ride.

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