B'Twin Rockrider ST 900 24" 9-12 Kids Mountain Bike

B'Twin Rockrider ST 900 9-12 Kids MTB

And a few ST 900 24" photos

Full Spec

We've designed this mountain bike for children aged 9 to 12 years (135 to 150cm) wishing to perfect their MTB techniques.

We've equipped this 24-inch mountain bike with an aluminium frame to make it lighter so children can take on any obstacle. The suspension fork and disc brakes mean they'll be able to go anywhere.

Ease of use: ALU frame and chainset for less weight.

Quick release for removing the wheels.

Brake control: Front/rear mechanical disc brakes: powerful braking in all conditions.

Efficiency: Suspension fork.

Skinwall tyres for less weight, with side knobs.

Cycling comfort: Sports saddle combined with an aluminium seat post for greater comfort.

A frame that is suitable 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: Brake effectively thanks to the mechanical disc brakes at the front and rear. The disc brake acts on the wheel axle to deliver powerful braking under any conditions (dry, wet, muddy, etc.).

Single Chainring Drivetrain: This bike is equipped with speed controls that are controlled using the thumb and index finger, allowing effortless changes between the 8 speeds. The single 36-tooth chainring and 11-34 cassette make it easy to shift gears and deal with any kind of hill. With just one control to manage, you can focus on your trajectory.

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. Suntour fork with 50 mm of travel.

Comfort when riding: 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: To hone your steering, we have equipped this mountain bike with a short aluminium stem (70mm) and a 540 mm oversize handlebar. This makes you more precise and responsive on turns.

Aluminium chainset: The new aluminium chainset has a 152 mm crank that is suited to the child's leg length. This light chainset allows you to start pedalling more easily. The double chain guard prevents the chain from derailing.

Double-walled rims and SkinWall tyres: The double-walled aluminium rims are light and durable. For transporting the bike, we've made it easy to attach/detach the front and rear wheels. They are equipped with a quick-release system.

The tyres use SkinWall technology. This process allows you to reduce their weight, therefore increasing performance, grip and comfort. 24-inch 1.7 to 2.2 cross-section inner tube with Schrader valve.Pressure indicated on the tyre sidewall (between 2 and 3.5 bar).

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

Dimensions of the bike ready to use: Length: 160cm.

Height: 100cm.

Width: 60cm.

Frame dimensions: Top tube length: 479.3 mm.

Seat tube length: 345 mm.

Chainstay length: 415 mm.

Seat post length: 370 mm.

Head angle: 68.2 degrees .

For the drive train parts (cassette and derailleur), the photos and videos provided on the product description show a Shimano Altus derailleur and a Microshift cassette. However, because of procurement issues, an equivalent, Microshift derailleur and cassette may be present on the bike.

Warranty: for life (frame, stem, handlebars, rigid fork).

Find out more about the bike guarantee.

Weight: 12.3kg.
.. more details.

B'Twin Bikes

B'Twin are a popular choice of bike in the UK, partly due to their widespread distribution by Decathlon, and partly due to the value they offer. Their bikes are divided into several slightly overlapping ranges, with Triban best known for road and gravel bikes, and Rockrider gaining a reputation for high performing MTBs to suit every budget. Elops largely consist of a range of city bikes, whereas Riverside focus on hybrids. All in all, B'Twin bikes are well worth checking out given the size of their ranges; there's a model to suit most budgets.

Rockrider Mountain Bikes

Rockrider are Decathlon's off-road offerings, comprising of a series of kids bikes and adult hardtails, full suspension steeds and even a handful of high end E-MTBs.

This brand was launched in 2018, when Decathlon decided to split their B'Twin bikes into different genres. In terms of prices, there's something for everyone, with adult's MTBs starting at just over £200 and rising up to high end lightweight race bikes at nearly the £4000 mark.

If you want to ride off-road, and would prefer to buy from Decathlon, then the Rockrider mountain bike range is for you.