27.5 Inch Mountain bike Rockrider ST 540 - Blue


This 27.5" mountain bike has been designed and developed to best suit mountain-bike rides lasting two to three hours, all year round, in any conditions.

Discover the effectiveness and playful side of the ST 540 with 27.5" double-walled rims, hydraulic disc brakes, and the simplicity of its 18-speed double chain wheels. All whilst staying comfortable.

Color: Deep blue / Fluo lime yellow
Size: size guide


Product benefits

Cycling comfort

Enjoy an upright position, adjustable stem, 100mm suspension and hammock saddle.

Directional control

Control your trajectory: hydraulic disc brakes, wide tyres and handlebar.


Ride efficiently thanks to 27.5" wheels, 18 speeds and light tyres.

Ease of use

Lock the fork in one quick step, and adjust the saddle effortlessly.

Lifetime warranty

Rockrider provides a lifetime warranty on the frame, stem and handlebar.

Technical information

Which is the right size?

Several sizes available:
S: between 1.50m and 1.64m
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).


With a heavily sloped top tube and a wide range of sizes (from S: 1.50m to XL:2.00m).

The ST 540 mountain bike frame is UNISEX.

The ST 540 mountain bike is available with the same frame in a WOMEN'S version: fitted seat, narrower handlebar, shorter stem, fork with a more flexible spring, and brake levers that are closer together.

As a WOMAN, if you choose the MEN'S model, we recommend at least purchasing the WOMEN'S SPORT 500 saddle which is fitted to the female form.


The ST 540 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: more progressive, powerful hydraulic disc brakes, 100mm travel in the fork to easily ride over obstacles, and simple and effective double chainring,...
MTBers have been involved at every stage of this bike's development process.


For less weight and more efficient pedalling, the Rockrider ST 540 MTB frame is made from 6061 aluminium (only 2.1 kg in size M).
Our designers created this bike to be comfortable and easy to manoeuvre. Its slope has been designed to keep your back straighter. The lower bottom bracket helps keep you more stable during turns.


Ride over obstacles with the hydraulic fork. Its 100 mm travel allows you to calmly overcome more obstacles (roots, pebbles, stones, mud).
Its built-in lockout system helps to prevent bobbing and loss of speed on faster terrain.


This mountain bike has no rear suspension.

This is a "semi-rigid" mountain bike. Compared to a full suspension mountain bike (with rear suspension), the advantages are clear: this mountain bike is lighter; less energy is lost on flatter ground. If however your primary concern is comfort and manoeuvrability, the ST 540 is available in a full suspension version with suspension at the rear.


2 9-speed chainwheels for 18 easy-to-use speeds.
The thru-axle bottom bracket is very stiff and long-lasting.

In detail:
-SHIMANO Altus 22 and 36 tooth double chainring
-MICROSHIFT FD-M462 front derailleur
-SHIMANO Altus rear derailleur
-SHIMANO Acera shifters with speed indicators
-MICROSHIFT H092 9-cog 11 to 36 tooth cassette
-KMC X9 chain


The adjustable stem brings the ST 540 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 Sport "soft touch" ergonomic grips for good grip and a comfortable feel.


Our teams designed and created an exclusive ROCKRIDER ERGOFIT saddle. Designed for all hip widths, its hammock shape is very comfortable for long, athletic rides. The Flex 27.2mm diameter aluminium seatpost also contributes to its increased level of comfort.

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 160mm 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.


The aluminium wheels are effective and sturdy: 27.5" diameter and double-walled rims. Their diameter is the perfect balance of comfort and performance. With their 28 spokes, they are lightweight, stiff, and durable.
The wide, ROCKRIDER ALL CONDITIONS (60 TPI) 27.5" x 2.1 tyres have side knobs designed for riding on all types of terrain (dry, wet, etc.).
Tubeless Ready 23 mm rims: SCHRADER valves, TUBELESS rim tape, TUBELESS tyres, and puncture-proof liquid to be added.

Platform pedals

The ST 540 comes with Rockrider Flat platform pedals with a wider pedalling surface and more pronounced dots for better grip on the pedal.


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 540 mountain bike is fitted with a bell, lights, wheel reflectors and pedals.

The frame is compatible with:
-500 chainstay stand (ref. 8302792)
-100 bottle cage (ref. 8049106) and 500 bottle cage (ref. 8358133)
-Mountain bike mudguard set (ref. 8385291)
-100 saddle bag (ref. 8347394) and 500 saddle bag (ref. 8354448)
-500 pannier rack (ref. 8364376)
-100 frame child seat (ref. 8486913 and 8487125), whatever the size


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.


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


S - 155-164cm : 13.5 kg
M - 165-174cm : 13.95 kg
L - 175-184cm : 14.05 kg
XL - 185-200cm : 14.2 kg
Weight without pedals.

Product concept & technology

Product Composition

Frame 100% Aluminium 6061


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.

User Directions

Not suitable for XC, All Mountain, Enduro and BMX.


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.


To have more informations about this product, consult the notice


27.5 Inch Mountain bike Rockrider ST 540 - Blue
27.5 Inch Mountain bike Rockrider ST 540 - Blue
27.5 Inch Mountain bike Rockrider ST 540 - Blue
27.5 Inch Mountain bike Rockrider ST 540 - Blue
27.5 Inch Mountain bike Rockrider ST 540 - Blue



Q:How to assemble your bike?

A: Everything you need to know about making sure your bike is comfortable, secure and ready to ride.

Q:Do you offer a Cycle To Work scheme?

A: Find out everything you need to know about way of getting to work that’s for good you and the environment. Check Here
Products sold and shipped by Partners are not eligible for Cycle to work Schemes

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