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ROCKRIDER ST 900 Full Suspension Mountain Bike - 27.5"

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was £749.99 -%


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£749.99 -%
This price includes a recycling fee for electrical equipment and batteries DecathlonDeeeTaxMentionAfterPrice / Since

* From To

* Sales from to Until end of stock
* From and limited stock
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The ST 900 is a great full suss MTB designed with the more adventurous trail rider in mind. This machine focuses on comfort and control. With it's exclusive lifetime warranty double butted 6061 FS alloy frame it really is built to last. It features double walled 27.5" rims and smooth running sealed bearing hubs, lockable 120mm travel Rockshox 30 Silver front forks and a 120 mm X-FUSION O2 PRO L rear shock. Equipped with up to date 1x11 gearing and tektro designed hydraulic disc brakes. The wider bars, hammock saddle and 2.2 wide tyres complete this fine package. Available in 3 sizes: S, M and L Weight: 13.6kg
Not Available Now

We currently have limited capacity to build bikes in our warehouse. Due to this, we are limiting the number of bikes we sell per day and you might not be able to process your order at checkout. The count resets at 11pm every day so that would be the best time to try, although we do have a peak of attempts at this time so we can't guarantee a slot for everyone.

Product benefits

Cycling comfort Enjoy an upright position, adjustable stem, 120mm suspension and hammock saddle.
Directional control Control your trajectory: hydraulic fork and brakes, air shock.
Efficiency 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.

Technical Information


Several sizes available:
M: between 1.65m and 1.74m
L: between 1.75m and 1.84m
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).


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.


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 fork 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.


For less weight and more efficient pedalling, the Rockrider ST 900 S frame is made from 6061 aluminium (only 2.5 kg in size M without suspension). It is 200g lighter than the ST 540 S frame thanks to its double butted front triangle.
Its 120mm rear shock uses a single-pivot system (more sensitive to small impacts, while remaining firm when encountering large impacts) and sealed bearings for a great lifespan.


The 120 mm Rockshox 30 Silver hydraulic fork is 400g lighter than that of the ST 540 mountain bike. It is conical and 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.


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.


The single chainring is easy and efficient to use.
1 chainring and 11 speeds: accelerate on the flat and take on climbs with no compromise.
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


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.


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 effort applied to the brake levers.
The aluminium brake levers are easy to grip, lightweight, and precise.


Lighter wheels: with sleeved double-walled rims and lighter tyres, these are 230g lighter than the wheels on the ST 540 S.
With 28 spokes, they are lightweight, stiff, and durable.
The exclusive ROCKRIDER ALL CONDITIONS LIGHT (60 TPI) 27.5"x2.2 tyres have side knobs designed for all terrain riding. A width of 2.2 means more grip on technical sections.
Tubeless Ready 23 mm rims: you will need rim tape, Schrader valves, and puncture sealant.


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.


We added a quick release system for easily removing/reattaching the front wheel.
Tip: 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, wheel reflectors and pedals.
The frame is compatible with:
-front and rear mudguards
-bottle cage
-saddle bag
An exclusive interface mounted on the stem lets you quickly attach the 120 and 500 Decathlon cyclometers, as well as Garmin, Sigma and Bryton cyclometers and GPS devices.


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 check of your bike. Just come to your nearest Decathlon workshop with your Decathlon card and/or receipt.


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


S - 155-164cm: 13.3 kg
M - 165-174cm: 13.4 kg
L - 175-184cm: 13.5 kg
XL - 185-200cm: 13.6 kg
Weight without pedals.

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Composition / advice

100.00% Aluminium 6061
Stock advice After washing, rub with a dry cloth to remove all traces of moisture. Store your mountain bike in a cool, dry place, away from corrosive products and salty air.
Restricted use : Not suitable for XC, All Mountain, Enduro and BMX.
Legal notice To ensure components last longer, we recommend a maximum load of 120 kg (rider and MTB included).

Our commitments

Test Product 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.
Guarantee : Lifetime (frame, stem, handlebar). Availability of spare parts: 2 years.


Q : How to assemble your bike?
Everything you need to know about making sure your bike is comfortable, secure and ready to ride.
Q : How do you adjust your brakes?
Having properly functioning brakes is vital when out on the road. Check out how to get them working to your liking.
Q : How to replace a brake lever on a bike?
Having properly functioning brakes is vital when out on the road. Here’s a video to show you how to make sure your new brake level is working nicely.
Q : How to replace a disc brake?
Having issues with your disc brake? Then this video is for you.
Q : How to adjust your bike handlebar?
A suitable handlebar height is essential to your cycling safety and comfort. Find out how to adjust it to your liking with our video.
Q : Do you offer a Cycle To Work scheme?
Find out everything you need to know about way of getting to work that’s good you and the environment.Check Here

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ST 900 Full Suspension Mountain Bike - 27.5
Maintenance and repair
Maintenance and repair
ST 900 Full Suspension Mountain Bike - 27.5"
Because you look after your own health, we look after that of your products: tips for initial settings, maintenance and repair advice, video tutorials, FAQs, instructions...
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