Ref: 8529457



We have designed this mountain bike for children aged 9 to 12 (135 to 150cm) who want to perfect their mountain biking skills.

Equipped with the same aluminium frame as the 24" ST 900, this mountain bike has an air suspension fork to adjust to the child's weight and hydraulic disc brakes for effective downhill braking


Brake barrel adjusters

There are two barrel adjusters on each brake, situated on the brake levers. They are used to adjust the tension of the brake cable. Make sure you get the setting right when using the barrel adjuster. (The more the barrel is tightened, the tighter the cable).

Derailleur barrel adjuster

This barrel adjuster is located to the rear of the derailleur. It is used to adjust the tension of the derailleur cable. If the chain struggles on climbs, it means the cable is not tight enough. Tighten it by unscrewing the barrel. If the chain does not run smoothly on descents, then the cable is too tight. Turn the barrel to slacken the cable. A quarter turn is often all you need.

Disc brakes

This mountain bike is fitted with front and rear mechanical disc brakes, guaranteeing powerful braking in all conditions.

Stem bolt screws

The two screws secure the stem to the head tube on the fork.


First use

Adjusting the height of the saddle before your first ride

It's important to adjust the height of the seat post and the handlebar to fit your child's height. The mark indicating the minimum insertion point of the seat post, or the handlebar, into the frame, should never be visible, for safety reasons (make sure that neither the seat post nor the handlebar extend past this minimum insertion level).

To determine the correct saddle height, sit your child on the bike with one heel resting on the pedal with the crank turned so that the pedal is at its lowest position. The saddle height is correct when the child's leg is extended while in this position. Also while seated, check that the child can touch the ground with their toes

What is the recommended pressure for 24" mountain bike tyres?

The recommended pressure is always indicated on the tyre sidewall. We recommend inflating your tyres to the pressure indicated on each tyre. This may vary from tyre to tyre. 

Check that the bike's tyres have enough air in them by simply placing your child in the saddle while the bike is stopped. If the tyre pressure is correct the tyre should go down ever so slightly with your child's weight. 


Compatible accessories

1. Front and rear mudguards
Fitting mudguards on a mountain bike
2. The stand
Fitting the stand
3. The bottle cage: fitting one on a mountain bike

Maintaining your 24" mountain bike

Lubricating the chain on a children's mountain bike

You can use an "all-in-one" type product (available at Decathlon stores) to unjam, clean, lubricate and protect your child's bike. It's a very handy product!

To lubricate the chain, turn the pedal and "spray" the product all the way along. 

Then leave it to dry for a few minutes. If the chain is very dirty, clean it with a brush and/or a cloth and spray it again with "all-in-one".


Our advice: to avoid getting the product on the brake pads and the braking surface on the rims.


Protect your bike: Apply all-in-one regularly to prevent rust from appearing.

Washing your child's mountain bike

If you notice that your child's bike is dirty after a few rides (mud, rain, dust, etc.), it's a good idea to take a few minutes to get it clean again.

 If it's covered in dust, simply use a dry cloth to clean it. If there's mud or other dirt that's harder to get rid of, you can clean it with a bucket of hot water, a sponge (or a cloth) and some soap or bike shampoo.  If certain parts of the bike are dirty (frame, fork, handlebars, wheels), wash those.

DID YOU KNOW?  We strongly recommend against using a pressure washer to wash your kids' bike. It may damage certain components (headset, bottom bracket, etc.) which could put your child at risk. 

When you've finished, simply wipe it dry with a cloth to prevent rust.

It's a good idea to apply fresh lubricant to the moving parts (chain, headset, bottom bracket).

How to check the condition of your tyres

You should always check the tyres before you take your bike out. 

If they're flat, check to see if they have a puncture. To do this, inflate them as much as they will go.

If they go flat quickly, you will have to take the wheel off and then the tyre, and change or repair the inner tube. 

If they go flat slowly, check the surface of the tyre for the presence of sharp objects or bits of glass. You will then need to take the wheel off and then the tyre, and change or repair the inner tube. Take care when removing the sharp object or shard of glass causing the puncture. 


If it is not flat, we recommend checking the pressure of the tyres (see section above). 


DID YOU KNOW? The useful life of rubber depends on how it is used and stored. If you can see cracks in the tyres, we advise you to replace them with new ones. 

How to store your bike

We recommend you keep your bike in a dry place.  You should check that it doesn't get damp.

The lifespan of your child's bike depends on how it is used, maintained and stored.

The more damp and saline the conditions, the more the child's bike will be prone to corrosion and the shorter its useful life.  

So it's important to keep it stored clean and dry in a place that is not damp. 


DID YOU KNOW? You shouldn't hang up bikes with telescopic forks by the front wheel. Hang them up by the rear wheel. This will ensure your fork lasts longer. 

Checking disc brakes for wear 

If you find that your brakes are not quite as responsive as when you bought the bike, it might be time to change the pads. 

As with car brake pads, the disc brake pads on bikes wear out and have to be changed. When checking the pads make sure there is more than a millimetre of braking material left on the brake pad. 

There is a problem

What to do if you have a puncture changing an inner tube

If you suffer a puncture, stop immediately in a safe place to prevent the rim from being damaged. 

Turn the bike upside down and set it down on the ground on the saddle and handlebars.

For the front wheel, remove from the fork and then change the inner tube (see explanatory video). 

For the rear wheel, position the derailleur on the smallest cog. Loosen the wheel and then change the inner tube (see explanatory video). 


As a last resort, you can always use puncture repair spray, with which you can repair an inner tube without tools, though this won't work if the inner tube is torn.

The gears are not shifting smoothly. what should be done?

If the gears aren't shifting smoothly, it's due to the rear derailleur not guiding the chain properly.

Check the cable and housing:

Housing ends that are out of position can obstruct the derailleur cable when it is being pulled and prevent the gears from shifting smoothly. If a housing end is out of position, push it back into place.

If the derailleur is not moving even after you have engaged and disengaged the grip shifter, it probably means that the cable and its housings have seized up. You will need to have the cable and housing replaced.

It's possible that the derailleur hanger has been bent or knocked out of shape. This makes it impossible to change gears. Our advice is to take the bike to the workshop at your nearest Decathlon store and have the hanger straightened. 

It's also possible that the derailleur isn't correctly adjusted. If that's the case, put the bike upside down on the saddle and handlebars and release the pedals (or preferably put it on a bike stand if you can). Activate the shifter/trigger (depending on your bike's configuration) to move the chain on to the smallest cog. The barrel adjuster is located to the rear of the derailleur. It is used to tighten and loosen the derailleur cable, respectively moving the derailleur up or down. Adjust the barrel until the gears shift correctly. 

The brake lever is touching the handlebars. what should be done?

If the brake lever is too slack, too limp, or touching the handlebar without much pressure being exerted on it, use the barrel on the brake lever to adjust the tension of the brake cable, as shown in the video below.


Loosen the barrel and the locknut to adjust the cable tension so that the brake lever is firm but not too hard.

Once you've got the tension right, tighten the locknut firmly against the brake lever to secure the setting. 


ROCKRIDER 24" 900 mountain bike red
ROCKRIDER 24" 900 mountain bike red

Our btwin commitments

ROCKRIDER provides a lifetime warranty on the frame, handlebar and stem of your mountain bike (under normal conditions of use).

All other parts have a two-year warranty.

When you start riding your bike, some components will move slightly. This is why we offer a free tune-up of your mountain bike within the first three months of purchase.