Decathlon 18-inch BMX

REF: 8501248



This BMX is designed for young riders (aged 7 to 9 / 1.25 to 1.35 m) learning to ride in the street, on street furniture and on pump tracks.

Here you'll find all our tips on setting up, servicing and repairing this BMX, along with all of the compatible accessories and spare parts.



The peg is an accessory that fixes to your BMX's axles. It enables riders to slide along street furniture and rails, and to perform tricks. Pegs can also be used as footrests.

Decathlon BMX
Compressionless brake cable housing

"Compressionless" brake housing, which is longer than normal, allows you to rotate the handlebars twice, i.e. 720° (compared with a detangler, which lets the handlebars rotate infinitely) while retaining the same braking power. This technology is used by the best pro riders, instead of a detangler!

compressionless brake cable housing
V-brake callipers

A V-brake is comprised of two callipers (one left calliper and one right). They are linked together in the middle. Pull the brake cable noodle out to release the callipers. This will allow you to remove the wheel easily.

V-brake callipers
Brake cable noodle


The brake cable noodle is a stainless steel part that is used to guide the brake cable into the V-brake calliper. The noodle is set at a specific angle to ensure the cable can slip into position and offer effective braking. It can be replaced if damaged.

brake cable noodle

First use

Adjusting the height of the saddle before your first ride

It's important to adjust the height of the seat post to fit your child. For safety reasons, the minimum insertion point marker on the seat post and handlebar should never be visible (make sure that you insert the seat post past this minimum insertion point).

In BMX, you're generally standing up, which is why the saddle is often very low.
If you're using your BMX bike only for getting around, or if your child is using it to have fun with friends, you can set the position higher for pedalling while sitting.You can of course switch between sitting and standing positions as you wish.

How should you set your bmx handlebars? 

A well-positioned handlebar is one that's perfectly perpendicular to the front wheel.

How to check that the brake pads are correctly adjusted 

To test the brakes, hold the bike by the handlebar and roll it forwards. Activate the right lever for the rear brake or the left for the front brake. The wheels should stop moving when the respective lever is pulled. The brake pads should not rub against the sides of the rim when the brakes are not engaged.

Here's what to do if you notice that the braking isn't smooth or the wheels rub on the brakes: There's an adjustment dial in front of the brake lever. If you turn the dial clockwise, that will tighten the brake (= more powerful braking). Turning the dial anticlockwise will loosen the brake (= weaker braking action and pads further from the rim).

It's important to regularly check that the brake is properly adjusted.


how to adjust v brakes

What is the recommended pressure for bmx tyres?

The recommended pressure is always shown on the tyre's sidewall. We recommend inflating your tyres to the pressure indicated on each tyre.
This may vary from tyre to tyre. Tyre traction is particularly important when turning and landing.

Compatible accessories

1. Pegs

You can add pegs to the front and back of this 20-inch BMX (footrests).

decathlon bmx pegs
How to mount pegs on the bmx

This is how to mount pegs on this bike:
1. Remove the hub guard
2. Screw the peg in by hand as far as it will go.
3. Then tighten with a screwdriver (as shown).

how to mount pegs on the bmx
2. Black bmx grips

Do you need to change the grips on your 18-inch BMX?
Find out which ones will fit your bike.

bmx grips
3. 18-Inch bmx tyre

This BMX comes with 18 x 2.1 tyres. 

red bmx tyre

Servicing your bmx

How to look after your bmx

You can use an "all-in-one" type product (available at Decathlon stores) to unjam, clean, lubricate and protect your BMX. It's a very handy product! To lubricate your BMX's chain, turn the pedal and "spray" the product onto the full length of the chain as it passes. Then leave it to dry for a few minutes. If the chain is very dirty, clean it with a brush or a cloth and spray it again with the "all-in-one" product. Our advice is to avoid getting the product on the brake pads and the braking surface on the rims.

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


Changing the brake pads

V-brake pads are available as spare parts. To change them, simply follow the steps in the video. 

How to check the condition of your tyres

We recommend checking the state of your bike's tyres before each ride.

If a tyre is flat, check that it isn't punctured. To do this, inflate your tyre as much as it will go. If it goes flat quickly, you will have to take the wheel off and then the tyre, and change or repair the inner tube.

If it goes flat slowly, check the surface of the tyre for the presence of sharp objects or shards 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.

TIP: To more easily identify where your inner tube is punctured, pump it up and then submerge it in water (in the sink, a washing-up tub, the bath, etc.). Slowly rotate the inner tube so that each part of it passes through the water. You'll see bubbles appearing in the place where the puncture is. Even if they're not flat, we recommend you check 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 clean your bmx

If you notice that your BMX 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.

Handy tip:
Before cleaning your bike, degrease the chain using a specialist degreaser.

 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, 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.

 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 store your bike

We recommend storing your bike in a dry place. You should check that it isn't getting damp.

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

The damper and saltier the conditions you use and store it in (e.g. by the sea), the more it'll rust and the less time it'll last.  It's therefore important to store it somewhere that's clean and dry, not damp. 

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.

Release the brakes to allow the wheel to come out. Squeeze the V-brake callipers together and release the noodle. 

For the front wheel, remove the wheel from the fork and replace 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.

Changing an inner tube on a child's mountain bike.

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. 


Our btwin commitments

BTWIN provides a lifetime warranty on the frame, handlebar and stem of this BMX (under normal conditions of use).

All other parts have a two-year warranty.

When you start riding your bike, some components will move slightly. It's for that reason that we offer a free check of your BMX three months after purchase.