27.5" ST 520 Mountain Bike - Grey

Ref. : 8511149

saddle: comfort that also yields greater efficiency. 27.5" wheels, double disc brakes, 24 speeds.

Comes with 8 speeds. Lifetime Warranty for the bike frame and fork.

Color: charcoal grey

  • S Out of Stock
  • M undefined
  • L undefined
  • XL Out of Stock

Our services :

  • Free delivery for Decathlon brands orders above $399
  • All Decathlon products are eligible for lifetime return

Products benefits

Cycling comfort

Raised position. Ergonomic saddle. Height-adjustable stem. Soft-touch grips.


CGF Evo aluminium frame. 24-speed SRAM X3. Light, 27.5" Aero Trail Evo wheels.


Dual disc brakes. Easy-handling frame geometry. Tyres have good grip in turns.

Ease of use

Innovative fork with easy adjustment based on rider's weight.

Technical information


The RockRider 520 was designed and created in Suzhou, China, by a team of experts and cycling enthusiasts dedicated to designing our MTB Sport Touring line.
Production was also done near Suzhou to be as close to our Decathlon stores as possible.


Rockrider CGF Evo (Comfort Geometry Frame) 6061 aluminium frame for 27.5" wheels.
Comfortable seating position thanks to raised steering.
Seat is 5 times more flexible than a standard frame thanks to a narrow 27.2 mm seat post.
Low bottom bracket: helps keep the mountain bike stable in turns, and makes it easier to place foot on the ground.
Open steering angle (69.5°): keeps mountain bike stable while riding.
Short rear wheel base: bike is easy to turn.LIFETIME WARRANTY on the frame!

Front suspension

B'Twin U-Fit 80 fork, with 80 mm of travel and an innovative fork stiffness adjustment based on the rider's weight (55 to 105 kg). Durable thanks to the materials and fabrication processes used.
Equipped with a mechanical spring and elastomer stoppers for maximum reliability and minimum maintenance.

Rear suspension

No rear suspension.


SRAM S200 triple-chainring chainset (22/32/42 teeth).
SRAM X3 8-speed rear derailleur.
Microshift MS22 front derailleur.
SRAM X4 shifters with speed indicators.
SRAM PG820 cassette, 8 cogs, 11 to 32 teeth.


Aluminium brake levers: lightweight and precise.
Front and rear HAYES mechanical disc brake callipers: powerful, progressive braking, even in rainy and muddy conditions.

Handlebar / Stem / Steering / Grips

B'Twin Sport Oversize aluminium handlebar; 660 mm (size S and M), and 680 mm (L and XL).
Semi-integrated A-headset headset—better sealed and integrated style.

B'Twin Sport handles with grooves, 120 mm long: genuine comfort while riding.


Aero Trail Evo aluminium wheels with double-walled rims: lightweight, stiff, and durable.
27.5" diameter: the best balance of comfort and performance.
Designed with 28 spokes to reduce weight while still ensuring rigidity and strength.


Exclusive B'Twin All Terrain Dry 27.5" x 2.0 tyres with a central tread specially designed for fast performance. Side lugs provide traction in turns. Also includes a chart showing recommended pressure levels depending on the rider's weight (see markings on tyre sidewalls).

Saddle / seat post

Exclusive B'Twin Ergofit Evo saddle offers outstanding comfort thanks to its wider "hammock" shape and good distribution of pressure points regardless of the rider's pelvis width. B'Twin Sport seat post in aluminium for less weight.
27.2 mm diameter provides the seat with a natural flex that's 5 times greater than a classic seat post.
400 mm long, offering a broad adjustment range.


Bike comes with mountain bike platform pedals with bearings, made from hard resin for lower weight and greater safety (less aggressive in case of pedal that slips).

Rider weight

Bike weight: 14.6 kg
Rider max. weight: < 100 kg



Product concept & technology

Product Composition

Bike frame 100% Aluminium


Store in a cool, dry place, away from corrosive products and salty air.


We also recommend that beginners wear cycling shorts with a protective pad and/or a gel saddle cover to reduce soreness.

User reviews

Questions & Answers