ST 100 MTB Cycling Helmet - Black


Easy to use and adjustable, this mountain bike helmet has been designed for your rides up to 1.5 hours.

The comfortable ST 100 helmet protects your head from branches and impacts. It comes with nine ventilation holes that are larger than normal, to offer you better ventilation.

Size: size guide


Product benefits

User comfort

Put on a well-fitting helmet with foam pads that you can forget you're wearing.


Adjust the helmet to your head using the adjustment dial.

Ease of use

Simplified adjustment, the straps are fixed under the ears.


Its 9 wide ventilation holes let air move through.

Impact protection

Complies with EN 1078.


Size M: 280 g Size L: 335 g

Technical information


9 vents.
Chinstrap fastening: clip
Occipital adjustment: dial.
Comfort foam: fixed (available from after-sales)
Visor: fixed, detachable
Outer shell: bonded polycarbonate.
Space requirements, size M: Length: 30 cm, width: 21 cm, height: 16 cm


To find your helmet size, simply measure your head circumference (around the forehead).
This mountain bike helmet is available in two sizes:
M: 53 - 57 cm
L: 57 - 62 cm


European standard setting out the requirements and test methods for helmets to be worn by users of rollerblades, skateboards, scooters and bicycles.
The corresponding requirements and test methods cover the following aspects: construction, including field of vision; shock absorption properties; characteristics of the retention system, including the chinstrap and tightening devices; marking and information.


We recommend replacing your helmet in 2 cases:

1/ After a fall
In the event of a fall, the material of your helmet can deteriorate or even break. Sometimes, you won't even notice. That is why we recommend replacing it if you have the slightest doubt.

2/ After 5 years of use
The foam of your helmet degrades over time. It can deteriorate due to impact, where it is stored, the climate, and its use. We recommend replacing your helmet at least every 5 years


Follow these 2 quick steps to adjust your helmet in 5 minutes:

1/ Clip the 2 straps with the buckle: check that you can still slide 2 fingers between the strap and your chin.

2/ Finally, adjust the tightness around your head.

The helmet should be in contact with your head, without tipping forward, backward, or sideways, even when you're moving.

Product tests

Our team of product designers based at the B'Twin Village in Lille is continuously working to make cycling more comfortable for our users.
Our obsession is to create products that meet the specific cycling needs of our users and eliminate things that get in the way of their rides.

A rating to compare products' environmental impact.

A product's environmental impact is calculated for its entire life cycle using various indicators.
An overall rating (ABCDE) is given, allowing you to easily identify products with the best environmental performance by comparing similar products to each other (T-shirts, trousers, backpacks etc.).

Decathlon openly displays the environmental ratings of its products.
To find out more:

Returns conditions for personal protective equipment

Make sure that this product fits properly.

If you do need to return it, you will need to make sure it still has its instructions, labels and, where applicable, original packaging. so that it can be reconditioned. Let's take care of our planet, together.


2 years

Product concept & technology

Product Composition

Foam 100% Expanded Polypropylene Shell 100% Polycarbonate Webbing 100% Polypropylene


Store the helmet in a dry place away from direct sunlight, and avoid high temperatures (> 60°C).
Clean the outside with a simple soft sponge and neutral soap.

User Directions

Suitable for skating & skateboarding. Not for motor sports.


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.A helmet is a piece of safety equipment: for this reason, we perform numerous tests on it, in particular, those required by safety regulations. This helmet complies with EN 1078 standard for cycling, skating and skateboarding helmets.


ST 100 MTB Cycling Helmet - Black
ST 100 MTB Cycling Helmet - Black
ST 100 MTB Cycling Helmet - Black

Customer reviews