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27.5" U-FIT Mountain Bike ST100 - Red

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Sale price: 106.000 KD

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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: 106.000 KD

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Product Features

A photo of the 27.5" U-FIT Mountain Bike ST100 - Red in use

Cycling comfort

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


An ultra-strong MTB: double-walled rims, welded saddle, derailleur guard.


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.

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Product Reviews

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1425 reviews

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ST 100

Summary/TL;DR - Buy from Decathlon. Ordered a colour the local store didn't have - no problem, took two or three days. I was ill and couldn't pick it up for a week - no problem, the staff weren't worried (and I hadn't even paid for it at that point). I turned up when I was ready, they set it up for my son to ride home, swapping quick releases for more secure versions, which gave us time to buy a better lock (there's plenty to look at in-store). The bike's as good as I'd hoped - standout feature at this price: front suspension that actually works and came with a set of little LED lights. And we got the bits that had been replaced. It was well set up. The only adjustments I made were raising the saddle slightly and adding a rear mudguard. The staff were helpful and informative throughout, neither pushy nor incompetent. Plus, both the bike and the skewers were reduced, so the whole thing cost less than I expected. Basically, this is your LBS (local bike shop) with international chain prices and stock. Recommended (have you seen the reviews their bikes are getting at the moment?!).

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David hobson

Great value for money

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Great bike for the kids starting in MB

Well made mountain bike and well designed with great build quality

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Squealing breaks

Got the bike a week ago in Farnborough store. When I choose the bike I wanted I noticed the tyres were flat and fron break was making a squealing noise. However I was assurred by a team member that before I get the bike they will do all the security checks for me and that it would take around 15 mins. After some time mh partner went to check if the bike was ready and once we got it we went downstairs to the till to pay. However I noticed the front breaks were still making that noise and we took ot back upstairs to the guy who was doing the " checks ". He did some adjustments to the breaks but also said that the breaks in all new bikes make that squealing noise . I've been using that bike for a week now as I cycle 9miles every day to work and I cannot use the front break at all!!! It is sooo noisy!!! My partner took the bike back to the shop today ( as it was.the only day I did not need the bike to get to work) he drove 20miles only tp be told they cant fix it now as they have too many bikes to fix and he could 've left it and picked it up tomorrow! But I need the bike tomorrow as it is only way to get to work and as Farnborough store is quite far away from.where we live my partner would not be able to pick it up tomorrow anyway as he is at work til late. Was so happy to get a new bike but it's been very stresful for me last week as buying a new bike I did not expect at all to have any problems with it !

I'm sorry to read that the brakes are squealing on your new bike. The local store should be able to help resolve this noise by doing what we call "to-in process" on the pads.
This is a link to a film which explains the process:
Peter, Cycling Manager, DECATHLON
For the kids

A superb bike with a fantastic price!

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Mountain Bike

Delighted with this product my son was overjoyed when he received it for his birthday. Is on this bike every day.

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Good entry level bike

Good bike with medium frame can suit 11 year old and upwards

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ST 100

Bought this for my 10 year old girl who absolutely loves it! Great looking bike for the price. She's only slight of frame and I was worried about the weight of the bike which isn't clearly identified on the web site, however she's been fine with it. Very pleased.

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Extremely good service and condition

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Best bike by far!

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Great all round bike

Great Bike all features needed to get out an enjoy the countryside!

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Nice bike

It’s nice bike to ride.

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Bike for 10 year old

Super present for 10 year old, he ha since invested in a saddle bag, mudguards and is prepared to cycle anywhere.

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Mountain bike

My son is very happy with this bike

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Rockrider 100

Hi got this bike for work I do 10 miles bike still good but when I tryed to get it out into 1st servis I was it was free for 1st one but no one was there to help me I was told to call the store but no one answered the phone bike is great but the store in north harbour needs to sort this problem out as now it's over the time limit for the free one

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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 1.65m and 1.74mL: between 1.75m and 1.84mXL: 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 have created an entirely new frame that is easy to step over.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 straighter whilst the rear has been shortened to ensure the bike is very agile when turning.

Front suspension

The 80 mm front suspension helps you get started with overcoming obstacles on slightly uneven trails easily.Easily adjust the hardness using U-Fit technology (weight adjuster). Simply set the number to your weight using the dial on the fork.

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: the 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 22-, 32- and 42-tooth chainring + protection from grease-Shimano TY500 front derailleur-Shimano TY300 rear derailleur-SRAM MRX grip shifters with speed indicator-7-cog, 14- to 28-tooth cassette-Wide, sturdy 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 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 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.

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. Great performance thanks to a central section with low rolling resistance and side knobs that 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 attaching/removing 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.Tip: a bike rack is an easy way to transport your mountain bike without dirtying your car.


Your ST 100 mountain bike comes with a derailleur guard, chainring guard (to keep your clothes from getting dirty), bell, lights, wheel reflectors, and pedals.The frame is compatible with:- Front and rear mudguards (Flash MTB or MTB 700)- Stand (500 Adult Base)- Bottle cage- Saddle bag- Rear pannier rack- Child seat (depending on the model)...

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 check of your bike. Just come to your nearest Decathlon workshop with your Decathlon card and/or receipt.

Legal disclaimer

To ensure components last longer, we recommend a maximum load of 120 kg (rider and MTB included).

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