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Rockrider ST520, 24-Speed Mountain Bike, 27.5"

Sale price: $499.00 Regular price:

Raised position., stem can be raised up to 1.18 in., ergonomic saddle: comfort that also yields greater efficiency. 27.5" wheels, double disc brakes, 24 speeds.

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Sale price: $499.00 Regular price:

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San Francisco, 735 Market St. Options

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About this item:

  • Shifter: 24-speed SRAM X3
  • Frame: Rockrider Comfort Geometry Frame
  • Brakes: Reliable Hayes MX5 mechanical disc brake calipers for powerful, progressive braking, even in rainy and muddy conditions.
  • Lifetime Warranty: Frame, stem, and handlebars guaranteed for life.
Model: 8629918

Product Videos

Product Features

A photo of the Rockrider ST520, 24-Speed Mountain Bike, 27.5" in use

Rockrider ST520, 24-Speed Mountain Bike, 27.5" | sporty mountain bike rides.

Raised position., stem can be raised up to 1.18 in., ergonomic saddle: comfort that also yields greater efficiency. 27.5" wheels, double disc brakes, 24 speeds.

Cycling comfort

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


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


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

Easy to use

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

Product Customer Reviews

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3015 Reviews
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Rockrider ST520, 24-Speed Mountain Bike, 27.5
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It’s pretty and easy to ride. However, there is little difficulty changing the speed for my bike, and the bell is little bit far from the hand.

Mountain bike

Good bike, very easy to put together (minimal build required) only just started to use it due to better weather, too early to tell if it stands the test of time, but so far so good.

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Awesome bike

Great service and high quality bike - son (12) is very happy with it

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Very good

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Awesome bike

Really like it, no problems as yet, happy

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Bought this bike but the right pedal wouldn’t tighten therefore cross threading the right crank arm now I have to go pay 45 pounds to get the bike check and make sure it’s say to ride aswell as rethredding the right crank arm. Very poor

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Very good love it, I’m no professionals cyclist but all good so far

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New 520 MTB

This bike is great value and more than I expected in terms of quality.

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Chain broke after a week of us seat lose not the best for money no shop opened by where we live to sort out

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Great value for money

Although I haven't had the bike for long, I've been very impressed so far. The spec offers great value for money and (touch wood) have had no problem keeping up with the kids on trails.

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Great bike

Well...people bitch about cheap bikes....But sometimes you don't get what you pay for! I looked for a mtb that did not cost to much but was worth buying and came across this bike. I have to say it is well made....looks great and worth every penny. It looks amazing but the stickers on the forks and wheels are not for me and the reflectors in the wheels so i removed them and now the bike looks less bling! It rides great and feels great. Well worth the money.

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Really good bike

I really enjoyed this bike, but I think that it would be better if it had more colour options

Rock rider

Bike is a good bike for starting into serious biking but pedals bit cheap easy to replace tho

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Great bike for the money

I wanted a bike to cycle the cycle paths of Hertfordshire, the odd trip to Thetford Forest and the odd trip up north. Great fun, perfect for what I want it for.

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I love the bike

The bike is soo great thanks

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Size Guide

Size Guide Visual

Additional Product Information


Bike frame

  • 100% Aluminum


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 aluminum 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 1.07-in. 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: bicycle is easy to turn. LIFETIME WARRANTY on the frame!

Front suspension

B'Twin U-Fit 80 fork, with 3.15 in. of travel and an innovative fork stiffness adjustment based on the rider's weight (121 to 230 lbs.). 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.


Tektro aluminum brake levers: lightweight and precise. Front and rear Hayes MX5 mechanical disc brake calipers: powerful, progressive braking, even in rainy and muddy conditions.


B'Twin Sport Oversize aluminum handlebar; 25.9 in. (Size S and M), and 26.7 in. (L and XL). Exclusive B'Twin aluminum stem, 70 mm (size S and M), and 80 mm (size L). Stem can be raised by up to 1.2", with 5 settings (+0", +0.3", +0.6", +0.9", +1.2"). Semi-integrated A-headset—better sealed and integrated style. B'Twin Sport handles with grooves, 4.72 in. long: genuine comfort while riding.


Aero Trail Evo aluminum 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 tires 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 tire sidewalls).

Saddle / seat post

Exclusive B'Twin Ergofit Evo saddle offers outstanding comfort thanks to its wider "Hammock" cut and good distribution of pressure points regardless of the rider's pelvis width. B'Twin Sport seat post in aluminum for less weight. 1.1". 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.


Bicycle 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).


31.63 lbs in S without pedals. 31.8 lbs in M without pedals. 32.1 lbs in L without pedals.


Frame can take a bottle cage, saddle bag, mud guard, stand, pannier rack.

User guide & bike assembly

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Warning - california prop 65

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Product testing

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

Storage instructions

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

Superior quality. Unbeatable prices.

For 40 years, Decathlon has delivered the best value in the retail sports industry by offering high-quality, sustainable and cost-effective products.

Decathlon makes the difference
  1. product-research

    Research and development

    delivers high-quality cost-effective products

  2. State-of-the-art production processes

    minimize manufacturing costs

  3. Optimized supply chain

    reduces retail prices

  4. laptop-checkout

    Minimal retail footprint

    lowers overhead and indirect costs


Size Guide Visual