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27.5" Mountain Bike ST 900 S - Grey/Yellow

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Sale price: Dhs. 5,375.00 Regular price:
Model: 8500764

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A photo of the 27.5" Mountain Bike ST 900 S - Grey/Yellow in use

27.5" Mountain Bike ST 900 S - Grey/Yellow : This 27.5" MTB is designed for MTB rides lasting over 3 hours, all year round.

Greater efficiency and more control: ROCKSHOX 120mm fork and air shock with handlebar lockout, single chainring, 27.5" lightened double-walled wheels, etc. Enjoy how lightweight the ST 900 S MTB is!

Cycling comfort

Enjoy the raised position, adjustable stem, 120mm suspension and hammock saddle

Directional control

Control your trajectory: hydraulic brakes and air fork and shock.


Smooth riding: lighter wheels, single chainring and suspension lockout.

Ease of use

Change speeds or lock your fork with a single motion on the handlebar.

Lifetime warranty

ROCKRIDER offers a lifetime warranty on the frame, handlebar and stem.

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Product Reviews

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362 reviews

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27.5" Mountain Bike ST 900 S - Grey/Yellow ROCKRID

Purchased this bike after visiting the store and after speaking to an assistant I decided on this bike. I have only had the bike out a couple of times but so far I am very pleased with the bike. Seems more that capable on the road and when I go off road.

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Soooo smooth

The suspension works its magic and your rides are extremely comfortable. This is a perfect bike for any occasion.

Rockrider ST 900S

Delighted with my new bike, This is easily as good as my Boarman I last owned at near 50% more to buy, Recommended to anyone who's looking for a great quality full suspension mountain bike

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This bike feels solid and handles well. It comes with inner tubes even though it says tubeless tyres, which is a big plus for me the last thing you want is the walk of shame for a puncture. The next bonus for me is the suspension rebound can be controlled from the handle bars. From soft to fully locked in progressive stages. The tyres seem to grip but they do squeek whilst doing it. Never heard that before. I'm 180cm and a large unit I went xl frame I'm glad I did. The front sproked has 32t which works but I will be changing to more teeth when I can. For 899 pounds what a brilliant bike. The service from decathlon has been excellent, (Wednesbury) the advice from the bike department was bang on. Many thanks to them.

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Brilliant bike.I couldn’t believe the amount of quality kit that comes with the bike! No compromise with this bike I would highly recommend this bike

Great Full Suspension Bike

Purchased for my 13 year old son - a great first full suspension bike

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Great all rounder

I’ve had this bike now for around 3 weeks, feels good quality and handles trails really well

Great bike.

I really like this bike, I have previously always had hard tail bikes but the cycle paths I use have started to deteriorate because of tree roots etc. So I though I would try a full suspension bike. Although I am just under 6ft I decided to go for the XL size, this was a good decision for me, it fits me perfectly. This bike is a joy to ride anywhere any time it smooths out roots and cobbles. Yes there is some pedalbob but it's not much and if I stand up to pedal I lock out the suspension. I found for the kind of riding I do, in that there are no really severe climbs the gearing was too low I was not using the bottom two gears at all and the top gear was not high enough. I replaced the front chainring from the 32T to a 34T I found this was perfect for me. Occasionally I do come to places that are more challenging (for me but I'm 64) this bike just soaks it up and flows through. I hadn't come across 'Microshifters' before I shouldn't have worried, the gear change is fast and accurate. I am very happy with one chainring at the front and 11 on the back it is a simple set up which just works and covers the range of gearing I want. The other nice little touch is being able to clip in a cycle computer to the head stem. Things I have changed, put on a 'crane bell', my old saddle because its comfortable I will change the pedals. Personally I feel this bike is excellent value for money and I love riding it.

Delivered damaged so will never know!

Bike was delivered with a large deep scratch on the frame, probably from transit. Customer service has been very slow to sort and while I would have kept the bike had I been given some money back (not a gift voucher), as it would cost me some to repair myself. Instead they will collect and no more stock, so I will purchase another manufacturer from another retailer. 1st and last time using Decathlon.

Great value for money for such a well equipped bik

I've only had three outings on this bike so far, but it's a very capable machine. Some of my rides take me through fields with stiles and it's easy to pick up and jump over. The adjustable shocks are easy to use and make the ride/bump impacts smooth. Brakes are strong, good range of gears for a 1x11 and lockable shocks make for a smooth ride on tarmac. My only issue is the missing cap from the top of the stem. I'd be grateful if this could be posted out please. Not enough of an issue to drop a star. Well worth the money.

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Not 100%

Bought on line with another bike for my son Both despatched at the same time. Arrived different days. Bike was not very well packed . Bike box flimsy and open. No instructions or paperwork included (lost?). On closer inspection noticed cable/hose frame clamps have been substituted for cable ties in three places and the rear tyre (directional) has been put on backwards. On riding the bike the drive feels like it is a bit clunky. The slack on the rear wheel spines is quite large so the pedals move a seemingly long way before engaging drive on the wheel. Not sure if this is going to cause a problem in the future or just be annoying. Have used it a couple of times on a gentle off road route with my son and it seemed to cope ok for this level. Haven't tried anything too extreme or quick just yet however it does seem sturdy enough at the moment. Overall a nice package just let down by simple finishing touches that would have made it 5 star for the price I would recommend, but maybe get it from instore where everything can be checked to make sure its correct first.

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Moderate Product

Handling is difficult, vehicle doest move much when comparing to other products. Like the full suspension, but performance getting reduced day by day. Handling should be increased, Weight should be reduced, Increase easiness to ride,

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Excellent product


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Best Cycle

This is best cycle in the market

quality product.

this is quite a quality . previously I have purchased xc 90 a Chinese product and it was costlier than quality this is far ahead of xc 90.

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Additional Product informations



  • 100% Aluminium 6061

Which is the right size?

Several sizes available:M: between 1.65 m and 1.74 mL: between 1.75 m and 1.84 mXL: between 1.85 m and 2.00 mIf 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).

Unisex frame

The ST 900 S MTB has a UNISEX frame.The ST 900's frame has been carefully designed down to the smallest detail, from the top tube's relatively pronounced slope, to the wide range of sizes (M: 1.65m to XL: 2m). The ST 900 S MTB is not only lightweight and comfortable, but UNISEX as well.To make the most of the improved comfort, the women on the Rockrider team recommend the 500 Women's Sports saddle, which is specially designed for the female form.

A word from the team

The ST 900 S mountain bike was fully designed and developed by our passionate MTB team at the B'Twin Village in France (Lille).A comfortable, efficient mountain bike: 120 mm ROCKSHOX air fork and shock to easily ride over obstacles, single chainring, and 27.5" double-walled wheels that have been lightened for greater efficiency.We've involved women mountain bikers at every stage of the design process.

A comfortable, playful frame

For less weight and more efficient pedalling, the ROCKRIDER ST 900 S 27.5" mountain bike's frame is made from 6061 aluminium (only 2.5 kg in size M, without shock), with a "double butted" front triangle that's 200 g lighter than that of the ST 540 S 27.5".Its 120 mm rear shock uses a single pivot system (more sensitive to small shocks, while staying firm for big impacts) and sealed bearings for a longer life.

Rockshox front suspension

The ROCKSHOX 30 SILVER 120 mm AIR shock is 400 g lighter than the one on the ST 540 S mountain bike. Its tapered steerer tube offers even more stiffness and precision when steering.Easily adjust the fork's bounce and stiffness.Its quick COMBO LOCK lockout system, which you can control from the handlebar, helps prevent bobbing and loss of speed on faster sections.

Rear air shock

This bike has a lightweight 120 mm X-FUSION O2 air shock that has been specially adapted to fit this frame. You can easily adjust it, based on your weight, using its Schrader valve.A special "high pressure" pump is required to adjust this shock (Rockrider fork and shock pump - ref: 3310286).Its quick COMBO LOCK lockout system, which you can control from the handlebar, helps prevent bobbing and loss of speed on faster sections.

Derailleur & drivetrain: a single chainring like the pros!

The single chainring is easy and efficient to use.1 chainring and 11 speeds:Accelerate on the flats and easily tackle the climbs. 1 single shifter on the handlebar: adapt your speed instantly like the pros as the terrain changes!In detail:-SRAM X1000 32-tooth single chainring-MICROSHIFT M665 11-speed rear derailleur-MICROSHIFT M8515 right shifter-MICROSHIFT H113 11-cog 11 to 46 teeth cassette-KMC X11 chain

Handlebars, stem, grips

The adjustable stem brings the ST 900 S 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 ergonomic grips for good grip and a comfortable feel.


Our teams designed and created an exclusive ROCKRIDER ERGOFIT Pro saddle. Designed for all hip widths, its hammock shape is very comfortable for long, athletic rides. The aluminium Rockrider Sport seat post is lightweight and has a wide adjustment range, with a 31.6 mm diameter and 400 mm in length.Quick and easy tool-free adjustment of your saddle height using the adjustment lever on the seat post clamp.

Hydraulic disc brakes

No matter what conditions you ride in (dry/wet), the Rockrider by Tektro 180 mm (front) and 160 mm (back) double hydraulic disc brakes will come through for you, even in the mud.Hydraulic braking adds more power and progressive braking and requires less powerful use of the brake levers.The aluminium brake levers are easy to grip and precise.

Wide, lightweight 27.5" wheels

Lighter wheels: with sleeved double-walled rims and lighter tyres, these are 230g lighter than the wheels on the ST 540 S.With their 28 spokes, they are also stiff, and durable.The ROCKRIDER ALL CONDITIONS LIGHT (60 TPI) 27.5"tyres have side knobs designed for all-terrain riding. A width of 2.2 means greater comfort and grip on technical surfaces.Tubeless Ready 23 mm rims: SCHRADER valves, TUBELESS rim tape, TUBELESS tyres, and puncture-proof liquid to be added.

Platform pedals

The ST 900 S comes with Rockrider Flat platform pedals with a wider pedalling surface and more pronounced dots for better grip on the pedals.

Easily transport and store your mountain bike

We added a quick release system for easily removing/reattaching the front wheel.Our advice: a bike rack is an easy way to transport your mountain bike without dirtying your car.


Your ST 900 S mountain bike comes with a bell, lights, computer & GPS mount on the stem, wheel reflectors and pedals.The frame is compatible with:-Bottle cage with side opening (ref. 8548543)-Mountain bike mudguard set (ref. 8385291)-100 saddle bag (ref. 8347394) and 500 saddle bag (ref. 8354448)

Comfort & safety

Your bike's fittings (chain, derailleur, brakes, etc.) will adjust over time. Take advantage of a free servicing within 6 months after purchase. Our technicians will carry out a 13-point inspection of your bike. Just come to your nearest Decathlon workshop with your Decathlon card and/or receipt.

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