27.5 Inch MOUNTAIN BIKE FULL SUSPENSION ROCKRIDER ST 900

This 27.5″ mountain bike has been designed and developed to best suit mountain bike rides lasting two to three hours, all year round.The lightweight ST 900 S bikes give you greater efficiency and more control, with ROCKSHOX 120mm fork and air shock with handlebar lockout, single chainring, and 27.5″ lightened double-walled wheels.

Which is the right size?

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

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.

Saddle

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.

Accessories

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.