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Mountain Bike Rockrider 520 - Dark Gray

Regular price $299.00 Sale price
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Regular price $299.00 Sale price

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San Francisco, 735 Market St. Options

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Model: 8378535

Product Features

Mountain Bike Rockrider 520 - Dark Gray is designed for regular mountain bike sport touring.

Raised position., stem can be raised up to 1.18 in., ergonomic saddle: comfort that also yields greater efficiency. 27.5" wheels, dual disc brakes., 24-speed: It has it all!

A photo of the Mountain Bike Rockrider 520 - Dark Gray in use

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.

Lifetime warranty

B'Twin provides a lifetime warranty on the frame, stem and handlebar.

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Product Customer Reviews

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4.2 out of 5 stars
5156 Reviews
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Rockrider review

Had mine a month now , from the Nottingham store . Very poor set up , got it out the car and pushing round to the shed the bottom mech rotated around the frame tube into the rear wheel ! Sorted it myself rather than a round trip back up the M1 . Front brake continues to squeak as wheel rotates , very annoying ! Gear change is not a patch on my old Rockrider which i used for 12 years . Disappointed . Wont be buying another , but i will put up with it for commuting and occasional Peak trails .


Son loves it!

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Great build shockingly badly built in store

This is a great spec bike for money. The build was so bad my son fell off straight away as the handlebars was adjusted so badly. The brakes and the seat both needed aligning too. Has put us off buying another. As long as you can adjust these things it’s great but not if you get one like ours.

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Shockingly poor quality

Bougth this bike for my 12 yo son ( against advised from Decathlon technical staffs who warned me about the fragility of the derailleur), was send home with a “See you in 3 months”...Straight home, my son went to the local park and 30 min within his outing, the derailleur broke...he came home late, carrying the bike....Very unsafe bike, complete lack of care by Decathlon who doesn’t monitor/react to feedback from their own technical staffs....Thank you to the Harlow cycling staff, shame on Decathlon for carrying on selling this bike...

I'm sorry to read that you had issues with the derailleur on this bike. All of the parts are selected have been tested by external specialists and undergo rigorous testing before being selected for our bikes. It may be that there was a fault with your particular derailleur and if it was a manufacturing issue, your local store will replace it under warranty for up to 2 years from the date of purchase.
I will contact the local store to get feedback on the matter.
Peter, Cycling Manager, DECATHLON

Great quality bike, haven’t really seen my son since purchasing it

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Rockrider MTB

Got an email to say the bike was ready to pick up but wasnt on arrival. Very helpful staff at hermiston gait built it for me on the spot. Great service. Email alerts need scrubbed up on!

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very poor bike

brought my first one was happy till next day the gears started to mess up i took back to the store the guy spent 25 mins on the bike to say there is a fault with the gear and offered a replacement so we wehn for the replacement had to wait 5 days and drive all way back tro the store to get the 2nd bike get home with the bike and same agen the grears woundnt work right and it was when they locked up the back wheel i could of got hurt so agen took it back for my money back

I'm very sorry to read of your poor store experience with this bike.  The gears should work with no issues. Whilst it's important not to cross the chain (small chainring, smallest sprockets and largest chainring and largest sprockets) they should shift and work with no issues. I'm sorry that the local store was not able to resolve these issues for you.
Peter, Cycling Manager, DECATHLON
Very good bike

I bought this bike as a general ride around. For the money, it is well made and looks good. The gears are nice and easy to see and use too.

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Great bike love it

Bought one of these 3 years ago and love it. Admittedly I'm not using it as a mountain bike instead I've put some 1.5 road tyres on it, mud guards, pannier rack mirrors etc and use it as a touring bike. So far I've done over 3000 miles on the bike including an 800 mile 8 day tour from Switzerland to the Hook of Holland. Had a couple of issues the axle worked loose on the back wheel causing a woble and the derailleur to jump gears but got it sorted in store over 1500 miles ago and still OK. Recently developed a but lateral movement in the bottom bracket which is being looked at now. But considering the mileage I think we can put that down to fair wear and tear, and a new bottem bracket fitted is less than £40,

Excellent bike for the money

Good modern geometry solid bit lightweight good commute and trail bike highly recommend


Great bike i Cycle regular mainly on the road can’t complain thus far

Great piece of kit I have bought 3 of these.

Great piece of kit I have bought 3 of these !

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Gear stopped to work

1st the bike seemed okay. But then later I realized that it was nearly impossible to get it to 3rd gear. Changing gears is often really hard as it gets stuck. Today when riding the bike I changed from 2nd to 1st gear, the chain fell off from the bike and as I was surprised I nearly crashed into a car. I try to quickly fix it on the side of the road by putting it back to the proper place. It worked for 10 minutes, but then I realized that whenever I try to change to any other gear some parts of the front gear shift blocks the tire hence it does not rotate. I called my nearest Decathlon where they told me that my only option is to go there. This means that I will have to walk 2 hours. For a bike that I used for around 20 hours so far. I will demand a full refund and never buy at Decathlon again.

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Dear Sir,
Thank you for taking the time to review your bike. As with many new bikes, the gear cables can stretch a little and for this reason we offer free checkups for customers in store within the first three months. This irons out any adjustment issues to be sure you have many miles of smooth riding ahead. Your local workshop will discuss this with you directly.
Peter, Cycling Manager, DECATHLON
Stunning Bike Comfy Ride

Comfortable Bike great value for first mountain bike smooth gear change

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Decent bike

2nd time buying this bike, really smooth, however at the start some visits to decathlon are needed in order to tackle some noises and some problems with the chain, but they manage to fix them appropriately & after that it’s a pleasure to ride, would highly recommend

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Additional Product Information


Bike frame : 100.0% Aluminium 6061


The ROCKRIDER 520 was designed and created in France, at the B'Twin Village in Lille, by a team of experts and cycling enthusiasts dedicated to designing our mountain bike Sport Touring line. Production took place in different factories in Europe as close to our Decathlon stores as possible. More information available on our website:


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.

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, 2.75 in. (Size S), 3.15 in. (sizes M/L), and 3.54 in. (size XL). Stem can be raised by up to 1.18 in., with 5 settings (+ 0 in., + 0.29 in., + 0.59 in., + 0.89 in., + 1.18 in.). 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 good grip 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. 1.07-in. diameter provides the seat with a natural flex that's 5 times greater than a classic seat post. 15.75 in. 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. 31.85 lbs in M without pedals. 32.07 lbs in L without pedals. 32.40 lbs in XL without pedals.


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

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.


Size Guide Visual