20 inch Kids Mountain bike rockrider st 900 6-9 years - Red


This mountain bike is designed for children who are aged 6 to 9 and looking for adventure. It's suitable for kids with heights between 120 and 135 cm.

For comfortable rides on rough terrain, we've equipped this 20" MTB with a suspension fork. Easily overcome slopes with the 6 speeds.

Color: Scarlet red

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Product benefits

Ease of use

ALU frame and chainset for less weight. Grip shifter for the 6 speeds.

Brake control

Front cable disc brakes: powerful braking in all conditions.


Suspension fork. Skinwall tyres for less weight, with side knobs.

Cycling comfort

Sport saddle combined with an aluminium seat post for added comfort.

Technical information

Frame designed for mountain biking

Our engineers have designed a new aluminium frame. Durable, lightweight and responsive: designed for tackling any obstacles when out mountain biking.

Controlled braking

Effective braking thanks to the cable-activated disc brake at the front and a V-brake at the rear.
The disc brake acts on the wheel axle to deliver powerful braking under any conditions (dry, wet, muddy, etc.).
The V-brake is composed of 2 levers equipped with pads that exercise more or less pressure on the rim to slow or stop the rotation of the wheels.

Front suspension to cushion unpredictable terrain

Take on new challenging terrain (roots, stones, gravel, etc.) with ease thanks to the travel of the front suspension fork.

Changing gear

This bike is equipped with a grip shifter to change between the 6 speeds: an easier, safer system as the child's hands stay on the handlebars.
This makes changing gears to match the terrain simple and easy!

Why have we created a brake lever specifically for children?

Because children have smaller hands than adults, it's not always easy for them to reach the brake lever. This is why our engineers designed a brake lever that is closer to the handlebars and thus easier to hold.

A reinforced, ergonomic saddle

A saddle with a sporty design, designed with care to adapt to the morphology of children. Combined with an aluminium seat post (sturdy and flexible) for even greater comfort.

Riding position

We equipped this mountain bike with a short aluminium stem (60 mm handlebar) and an oversized 520 mm handle for more controlled steering. This makes you more precise and responsive on turns.

Aluminium chainset

The new aluminium chainset has a 140 mm crank that is designed for a child's leg length. This light chainset allows you to start pedalling more easily.
The double chain guard prevents the chain from derailing.

20" wheels and MTB SkinWall tyres

The tyres are designed for mountain biking. The lateral lugs provide good grip on turns. The tyres use SkinWall technology. This process reduces their weight and makes them more flexible, which increases performance, grip and comfort.

The recommended tyre pressure is displayed on the tyre sidewall (between 2 and 3.5 bar).

20-inch 1.7"-2.2" wide inner tube with Schrader valve.

Bike accessories

This MTB is equipped with a bell, lighting, wheel reflectors and platform pedals.

The frame is also compatible with other B'Twin accessories:
- front and rear mudguards
- stand
- bottle cage
- saddle bag
- stabilisers: https://www.decathlon.co.uk/20-and-24-stabilisers-id_8550741.html

Dimensions of the bike ready to use

Length: 140cm.Height: 80cm.
Width: 54cm.

What if I order online?

For smoother shipping, our bikes come with their pedals removed and the handlebar unscrewed (instructions and tools are supplied)

Frame dimensions

Top tube length: 433.4 mm
Seat tube length: 285 mm
Chainstay length: 360 mm
Seat post length: 300 mm
Head angle: 69°

Washing instructions

In order not to damage your bike, we do not recommend the use of a high pressure cleaner. Rinsing with clear water and a sponge is preferable.


Due to the current health crisis, some pictures are not contractual. The derailleur guard is not supplied with the bike and the stem is only equipped with a spacer for height adjustment.


for life (frame, stem, handlebars, rigid fork). Find out more about the bike guarantee.


10.5 kg

Product concept & technology

Product Composition

Frame 100% Aluminium


Store the bike in a clean, dry place. Clean and grease the chain regularly. Our tips for before each ride: inflate the tyres to the pressure indicated on the sidewall.

User Directions

We recommend wearing a helmet.Maximum weight in use 80 kg


To have more informations about this product, consult the notice


20 inch Kids Mountain bike rockrider st 900 6-9 years - Red
20 inch Kids Mountain bike rockrider st 900 6-9 years - Red
20 inch Kids Mountain bike rockrider st 900 6-9 years - Red
20 inch Kids Mountain bike rockrider st 900 6-9 years - Red
20 inch Kids Mountain bike rockrider st 900 6-9 years - Red
20 inch Kids Mountain bike rockrider st 900 6-9 years - Red
20 inch Kids Mountain bike rockrider st 900 6-9 years - Red
20 inch Kids Mountain bike rockrider st 900 6-9 years - Red


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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