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Rockrider 27.5 Inch Mountain bike Rockrider ST 100 - Yellow

Last checked price £229.99


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Current Offers By This Merchant Current Offers from DECATHLON UK

* Prices need to be checked at the Merchant's website as they may have changed

Quote from The Merchant's Website:

"This 27.5" mountain bike has been designed and developed to best suit getting started with mountain-bike touring in dry weather, for rides of up to 90 minutes.

With this bike's lightweight aluminium frame and 27.5'' tyres on double-walled rims (26" in XS), you can easily get through obstacles. It is a bike that is both effective and strong."

  • Cycling comfort: Enjoy touring: raised position, 80 mm suspension, hammock saddle, FLEX seat post
  • Robustness: An ultra-strong MTB: double-walled rims, welded saddle, derailleur guard.
  • Efficiency: Light frame, 21 speeds, 27.5" wheels (XS 26"), tyres with low rolling resistance
  • Directional control: Control your trajectory: V-Brake pads, tyres with side knobs
  • Lifetime warranty: ROCKRIDER offers a lifetime warranty on the frame, handlebar and stem.

Which is the right size?

  • Several sizes available:
  • XS:between 1.40m and 1.54m
  • S: between 1.55m and 1.64m
  • M: between 1.65 m and 1.74 m
  • L: between 1.75 m and 1.84 m
  • XL: between 1.85m and 2.00m
  • To adapt the MTB to your height and size, try these tips:
  • 1/ Sitting on the saddle, you should be able to touch the ground with the tips of your toes.
  • 2/ To adjust the saddle height, your knee should be slightly flexed with the foot on the pedal in the lowest position.
  • 3/ If you're between two sizes, choose the larger size.


  • With a very marked slope on the top tube and a wide range of sizes (from XS:1.45m to XL:2.00m),
  • The ST 100 mountain bike frame is UNISEX.
  • The ST 100 mountain bike exists with the same frame in a WOMEN'S version: fitted seat, narrower handlebar, shorter stem, fork with a more flexible spring, and brake levers that are closer together.
  • As a WOMAN, if you choose the MEN'S model, we recommend at least purchasing the WOMEN'S SPORT 500 saddle which is fitted to the female form.


  • 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.


  • It isn't always easy to get the right position on a mountain bike. Our designers created a frame that's easy to get onto.
  • The 100% aluminium CGF frame (Comfort Geometry Frame) is both comfortable and easy to handle. The slope angle has been designed to keep your back straight, while the rear bases were shortened to make the bike very agile in turns.

Front suspension

  • The 80 mm front suspension helps you get started with overcoming obstacles on slightly uneven trails easily.
  • Its mechanical spring is a stamp of reliability. And the fork is particularly easy to maintain.
  • To adjust the stiffness? It's very easy using a single dial.


  • This mountain bike has no rear suspension.
  • It is a "semi-stiff" 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; you spend less energy on flat ground.


  • 3 x 7 speed chainrings, 21 speeds total!
  • 2 easy-to-use grip shifters on the handlebar.
  • Left (chainrings): control ascents/descents.
  • Right (speeds): more precise control over your pedalling.
  • In detail:
  • -Triple-chainring chainset (22/32/42 teeth) + protection / grease.
  • -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


  • With a stem that tilts 10° upwards, the riding position of the ST 100 is raised, accessible, and comfortable.
  • In detail:
  • -Aluminium stem, 90mm long, with a 10° angle for maximum comfort.
  • -620mm wide steel handlebar, for stability and control.
  • -Grips in "soft touch" material' for good grip and a soft comfortable feel.


  • The saddle of the ST 100 is welded to prevent any movement of the saddle.
  • 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 (350mm or 400mm long depending on the bike size). Its smaller 27.2mm diameter provides your seat with natural flexibility, 30% more than a standard solution.


  • Two V-Brake pads for effective braking.
  • These brakes are composed of callipers that exert more or less pressure on the rim to slow or stop the rotation of the wheels.
  • Thanks to the special design of the ST 100's aluminium brake levers, you only need two fingers to brake.


  • The wheels of the ST 100 are tolerant and robust, with 27.5" double-walled 28-spoke rims (26" for the XS size). Start overcoming obstacles fearlessly, including small rocks, cracks, holes and bumps!
  • Because you're getting started with MTB touring on dry ground, this mountain bike is equipped with DRY 27.5 x 2.0 tyres. Their performance is optimised thanks to the rounded central section, whilst the side lugs provide good grip on turns.

Platform pedals

  • The Rockrider ST 100 mountain bike is supplied 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.


  • We added a quick release system for easily removing/reattaching the front wheel.
  • There is 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 dirtying your car.


  • Your ST 100 mountain bike comes with a chainwheel guard (to protect your clothing from dirt), bell, lights, wheel reflectors and pedals.
  • The frame is compatible with:
  • -500 chainstay stand (ref. 8302792)
  • -100 bottle cage (ref. 8049106) and 500 bottle cage (ref. 8358133)
  • -Mountain bike mudguard set (ref. 8385291)
  • -100 saddle bag (ref. 8347394) and 500 saddle bag (ref. 8354448)
  • -500 pannier rack (ref. 8364376)
  • -POLISPORT GROOVY frame-mounted baby seat (ref.8385622), from size S


Your bike's fittings (chain, derailleur, brakes, etc.) will adjust over time. Take advantage of a free servicing within 3 months after purchase. Our technicians will carry out a 13-point inspection of your bike. Just come to your nearest Decathlon workshop with your Decathlon card and/or receipt.


As for the 7 cog cassette with 14 to 28 teeth, the photos or videos on the description of the bike show a SHIMANO TZ500 cassette. However, due to supply difficulties, the bike can be equipped with an equivalent WHEELTOP cassette .


  • XS - 140-154cm : 15.3 kg
  • S - 155-164cm : 15.4 kg
  • M - 165-174cm : 15.5 kg
  • L - 175-184cm : 15.6 kg
  • XL - 185-200cm : 15.8 kg