XS: between 1.40 m and 1.54 m
S: between 1.55 m and 1.64 m
M: between 1.65 m and 1.74 m
L: between 1.75 m and 1.84 m
XL: between 1.85 m and 2.00 m
To adapt the bike to your height and size, try these tips:
1. You should be able to touch the ground with the tips of your toes when sitting on the saddle.
2. When your foot is on the pedal in the lowest position, your knee should be slightly flexed.
3. If you're between two sizes, choose the larger size.
With the very pronounced slope of the top tube and a wide range of sizes (from XS: 1.45 m to XL: 2.00 m),
the ST 100 mountain bike frame is unisex.
The ST 100 mountain bike exists with the same frame in a women’s version: adapted seat, narrower handlebars, shorter stem, fork with a more flexible spring, and brake levers that are closer together.
If you’re a woman choosing the men’s model, we recommend purchasing the women’s Sport 500 saddle, which is adapted to women's bodies.
A word from our team
We created this ST 100 mountain bike at our B'Twin Village (Lille, France) especially for mountain biking enthusiasts.
Recreational mountain bikers told us they wanted comfort, effectiveness, and durability. Those features were our starting point as we designed, developed, and tested the ST 100 mountain bike, with real riders involved throughout the project.
A lightweight, comfortable, fun frame
It isn't always easy to get the right position on a mountain bike. Our designers have created an entirely new frame that’s easy to step over.
The 100% aluminum CGF frame (Comfort Geometry Frame) is both comfortable and easy to handle. The steep top tube angle keeps your back straight while the rear tube has been shortened to make the bike very agile when turning.
The 80 mm front suspension helps you overcome your first obstacles on slightly uneven trails with no worries.
Its mechanical spring is a stamp of reliability. And the fork is particularly easy to maintain.
Can its stiffness be adjusted? It's very easy to adjust using a single dial.
Rear suspension: none
This mountain bike has no rear suspension. This is a "semi-rigid" mountain bike: perfect for beginners launching themselves into their first mountain bike touring rides. Compared to a full suspension mountain bike (with rear suspension), the advantages are clear: this mountain bike is lighter and less energy is lost on level ground.
Derailleur and drivetrain:
3 x 7-speed chainrings for 21 speeds!
Two easy-to-use grip shifters on the handlebars.
Left (chainrings): control ascents/descents.
Right (speeds): more precise control of your pedalling.
-Triple-chainring chainset (22/32/42 teeth) + anti-grease protection.
-Microshift FD-M20 front derailleur
-Microshift RD-M25 rear derailleur
-Microshift MS25 grip shifters with speed indicators
-Shimano TZ500 7-cog cassette, 14 to 28 teeth
-Large, solid KMC Z51 chain
Handlebar, stem, and grips:
With a stem that tilts 10° upwards, the riding position of the ST 100 is raised, accessible, and comfortable.
-90mm (in sizes XS and S) or 110mm (in sizes M, L, and XL) aluminum stem with a 10° angle for maximum comfort
-620mm-wide steel handlebar for stability and control
-”Soft-touch" grips for a firm yet soft and pleasant grasp.
The saddle of the ST 100 is welded to prevent movement.
And because your comfort is our priority after your safety, we've added an exclusive wider Ergofit saddle with a hammock shape.
Easily adjust the height of your saddle with the Flex steel seat post (350 mm or 400 mm depending on the bike size). Its smaller 27.2 mm diameter provides your seat with natural flexibility—30% more than a stand saddle.
V-brakes with pads:
Two V-brake pads for effective braking.
These brakes are composed of callipers that exert more or less pressure on the rim to slow down or stop the rotation of the wheels.
You only need two fingers to brake thanks to the special design of the ST 100's aluminum brake levers.
27.5" wheels and tires for dry terrain
The wheels of the ST 100 are durable and robust with 27.5" double-walled 28-spoke rims (26" for the XS size). Start overcoming obstacles like small rocks, cracks, holes, and bumps fearlessly!
Because you're getting started with MTB touring on dry ground, this mountain bike is equipped with Dry 27.5 x 2.0 tires. Great performance thanks to a central section with low rolling resistance and side knobs that provide good grip on turns.
The ST 100 Rockrider mountain bike comes with hard resin platform mountain bike pedals for added lightness and safety.
If your foot slides on the pedal, there's less risk of injury.
Transport and storage:
We added a quick-release system for easily attaching/removing the front wheel.
There’s a nut at the back to secure the bike and limit the risk of theft. You will need a spanner to remove the rear wheel.
Our advice: a bike rack is an easy way to transport your mountain bike without getting your car dirty.
Your ST 100 mountain bike comes with a derailleur guard, a chainring guard (to keep your clothes from getting dirty), a bell, lights, wheel reflectors, and pedals.
The frame is compatible with:
-Front and rear mudguards (Flash MTB or MTB 700)
-Stand (500 Adult Base)
-Rear pannier rack
-Child seat (depending on the model)
-and much more
Comfort and safety
Your bike's components (chain, derailleur, brakes, etc.) will adjust over time. Take advantage of a free servicing within 6 months after purchase. Our technicians will carry out a 13-point check of your bike. Just come to your nearest Decathlon workshop with your Decathlon card and/or receipt.
To make components last longer, we recommend a maximum load of 120 kg (rider and MTB included).
For more information on how to use and care for your Suntour fork, please visit the Suntour website.
You can download the user manual for your fork at: