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27.5" Mountain Bike ST 100

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Sale price: Dhs. 1,475.00

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This 27.5" mountain bike is designed for getting started with MTB touring in dry weather, for rides up to 1.5 hours.

Effective? Strong? Both please! Easily get through your first obstacles: lightweight aluminium frame and 27.5'' tyres on double-walled rims.

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Sale price: Dhs. 1,475.00

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Product Features

A photo of the 27.5" Mountain Bike ST 100 in use

Cycling comfort

Enjoy touring: raised position, 80 mm suspension, hammock saddle, FLEX seat post


An ultra-strong MTB: double-walled rims and welded saddle


Light frame, 21 speeds, 27.5" wheels (XS 26"), tyres with low rolling resistance

Directional control

Steering control: V-Brake calipers, tyres with side knobs

Lifetime warranty

ROCKRIDER offers a lifetime warranty on the frame, handlebar and stem.

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Product Reviews

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8429 reviews

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Great Bike

This bike for the few months I have had it has helped through my high intensity training. Definitely would recommend this bike if you are up for both road and off road cycling.

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Great bike at good price.

11 year old daughter loves this bike and believe me she is very very particular about everything she chooses. Well made and great design. She has been out on it everyday since we bought it . Great exercise and less time on the iPad . Would recommend.

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Solid bicycle

My (second hand) triban 500se was stolen last week and i immediately went to Decathlon in Surrey Quays to find another commuter replacement. The triban was bulletproof and rode as straight as an arrow for 1000's of miles, even as a second hand purchase from a market. The ST 100 seems to measure up to the old horse. It is very easy to ride and very sturdy for a heavier rider like myself. The only small fault I have is the seat post slides downwards a little after miles of bumpy riding an cobbled roads and needs readjustment. The rear brakes need running in and squeak raucously on the first braking. However, so far so good. Any developing problems can be rectified by the store, who will give it a going over within 3 months of purchase. The Decathlon store in Surrey Quays is very well equipped and the staff are very professional and helpful. Well done and keep up the high standards.

moutain bike exallant value for money

very exallant bike would buy another one exallant value for money

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decent mountain bike poor service from bolton

really decent mountain bike for price , I decided to buy looking at it on your website so I went down to my local store tried out the bike the person in the bike department was really good brilliant,on trying it out I decided to go for it so I bought it its been really good , my wife also like the looked of it once I got it and said she wanted one so I went down to my local store the person who works in the bike department was very rude which was a surprise to us as such I left the store without buying the bike today I am very disappointed as I have found your staff at the Bolton store really helpful and polite but not on this visit.

B’twin Mountain bike

Great bike . Well set up by sales staff

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Quality bike for the money

Quality bike for the money, great service when purchasing too

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Good support and knowledge

Lovely man who looked after us thankyou

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Bike is decent budget/entry level for my 9yo until he is of an age/skill level to need a higher spec. Bit heavy but you get what you pay for. Frustration was the bike has been back twice in the first few weeks as a wheel was not properly built and buckled due to loose spokes, then the gear cables came loose. Guys in store in Edinburgh repaired free and quickly twice but took the shine off the new Christmas present for son.

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I'm sorry to read that there was an issue with the wheel for this bike. This information will be forwarded to the Rockrider team at Decathlon who manage the wheel production. I'm pleased to see that the Edinburgh store resolved the buckle.
Peter, Cycling Manager, DECATHLON
Mountain bike

They are very helpful but could do with more experienced staff.

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Bad Mountain bike

I purchased this mountain bike and it is not working properly, It makes a lot of noise and not good to drive. Got punctured on its 5th day of driving. not recommended to buy

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Thank you for taking the time to post a review of your bike. All Decathlon bikes are offered a free checkup anytime in store within the first three months to make sure that the bike is running smoothly. Your local workshop in Cambridge will be more than happy to check the bike for you.
Peter, Cycling Manager, DECATHLON
Scratched frame, tight gear shift

We are quite pleased with the bike overall, however on delivery the frame was scratched and one of the frame stickers chipped. We have been out on three rides and the gears are very tight and have difficulty selecting. We can't get the gear to shift onto the smallest chainring, the gears are not set correctly. Maybe I am a little naive but I would have expected the bike to work. We are considering changing the gear selector as they are so tight and hard to use.

Bike ok but needs to go back and get gears fixed

This is a very good bike for the money but the bike was meant to have been check before getting but when we got it home and tried it out we found the gears are not working right


Absolutely spot on. Can't fault this bike. Gets me from a to b without any problems and is actually quite comfortable. Feel solid and no sign of poor manufacture.

Rockrider ST 100 Small Adult

Knowledgeable & Efficient Cycling Staff Sized properly and safely for our 9 yr old (tall) with longevity in mind. This bike should last him a long time.

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Additional Product informations



  • 100% Aluminium

Which is the right size?

Several sizes available:XS:between 1.40m and 1.54mS: between 1.55m and 1.64mM: between 1.65 m and 1.74 mL: between 1.75 m and 1.84 mXL: between 1.85m and 2.00mTo 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.

Unisex frame

With a very marked slope on the top tube and a wide range of sizes (from XS:1.40m 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.

A word from the 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 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.

Rear suspension: none

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.

Derailleur & drivetrain:

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

Handlebars, stem, grips

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.

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 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.One a year, check how the pads are wearing. If the grooves are disappearing, take your bike to your local store's workshop.

27.5" wheels & tyres for dry terrain

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.

Transport & storage

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

Comfort & safety

Your bike's fittings (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 inspection of your bike. Just come to your nearest Decathlon workshop with your Decathlon card and/or receipt.

Photos non binding

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 .

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