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Rockrider ST100, Mountain Bike, 27.5"

Sale price: $399.00 Regular price:

Comfort first: CGF frame with raised position, 80 mm suspension, Ergofit hammock saddle with Flex stem, 27.5" wheels (26" in XS") so you stay comfortable as you ride.

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Size Guide
Sale price: $399.00 Regular price:

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San Francisco, 735 Market St. Options

Select an available color and size to see options.

Model: 8675357

Product Features

A photo of the Rockrider ST100, Mountain Bike, 27.5" in use

Rockrider ST100, Mountain Bike, 27.5" | making it easy to enjoy the great outdoors on two wheels!

Comfort first: CGF frame with raised position, 80 mm suspension, Ergofit hammock saddle with Flex stem, 27.5" wheels (26" in XS") so you stay comfortable as you ride.

Cycling comfort

Enjoy: the high position (CGF frame), 80mm suspension, hammock saddle, flex stem


Progress: light frame, 21 speeds, 27.5" double-walled wheels (26"1 wall in XS)


Control your path with tires with side lugs and V-brakes.

Product Lifestyle Image Gallery

Image Gallery

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5 

Rockrider ST100, Mountain Bike, 27.5

Product Customer Reviews

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Rockrider ST100, Mountain Bike, 27.5
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Chain broken

The chain broke after less then a month of use! Bike looked nice and gears worked good. Chain kept coming off, it finally broke.

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Hi Jf,

Thank you for reviewing our product. We are sorry to hear that the chain on your bicycle broke. You can always bring your bike to the workshop at the Decathlon Ottawa store to get the chain fixed or replaced. Our staff will take a look to identify the problem and will work to find the best solution for you. We hope to see you again soon!


Emmanuelle Daoust

Sport Leader, Decathlon Ottawa

Good bike to consider

It’s a good bike though it’s not much a long time that I have this bike for my son. I just gave 4 stars because of its seat, that becomes loose after some time. That is only problem I find, Otherwise 5 star

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No problem so far

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thumbs up

my son loves this bike!

Enjoyable Ride

I have been riding this bike for more than a year, and I still love it. Light weight and durable commuter. In my free times, I really enjoy long distance and rides with fellows.

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Thank you Dear ! You are always welcome :) 

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
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Size Guide

Size Guide Visual

Additional Product Information


Bike frame

  • 100% Aluminum

A unisex sport bike

Available in a variety of sizes (XS: 4'9" ~ XL: 6'7"), the CGF frame is lightweight, comfortable, and versatile

How to choose the size of your bike?

S: 5'1" ~ 5'5" M: 5'5" ~ 5'9" L: 5'9" ~ 6'

Front shock absorber

The 80 mm SUNTOUR XCT front shock absorber is designed for rugged pavements, helping beginners easily cope with sporty bike rides. Mechanical springs are designed to be reliable and easy to maintain.

Transmission system

3 x 7 speed sprocket, 21 speed! Three-chain sprocket wheel (22/32/42 teeth) + grease protection - Microshift front derailleur - Microshift rear derailleur - with speedometer Microshift hand shift lever - 7 gears, 14~28 teeth Shimano sprocket

Horizontal / handle / handle

The ST100 sport bike has a 10° angled handle for a higher operating position and is easy to operate and comfortable.

Saddle: comfortable!

The stable seat is fixed (welded) to prevent movement during riding. In addition to safety, comfort is also a top priority for us. This sport bike features a unique wider Ergofit seat for the hammock shape. The flexible steel seat tube facilitates height adjustment of the seat and is 350 mm or 400 mm in length (according to the size of the bicycle). The reduced 27.2 mm diameter gives the seat a natural flexibility, higher than the standard.

27.5-inch wheels and tires for dry floors: are you ready?

Don't worry about obstacles when slowing down: small stones, cracks, small holes, and bumps on the road! The ST100 bike wheel is durable and has a 27.5-inch double-layer 28 spoke rim that is suitable for beginners to ride on dry roads, so the Dry 27.5 x 2.0 tire is more suitable. The circular center area provides excellent performance and the side lugs provide good grip when cornering.

Convenient bike transportation and storage

Considering that you may need to transport or store your bike in a limited space (car trunk, porch, etc.), we have equipped it with a front-wheel quick release. The rear wheel of the bike has a fixing nut that reduces the risk of being stolen. To remove the rear wheel, you need a wrench.


33.7 lbs, XS 34 lbs, S 34.2 lbs, M 34.4 lbs, L 34.8 lbs, XL *excluding pedals

Warranty information

Lifetime warranty on manufacturing defects for all metal frames, rigid forks, stems, and handlebars 5 years warranty on all carbon frames & forks 2 years warranty on all other parts Excludes damages arising from normal wear and tear, misuse, negligence, and unauthorized modifications"

Compatible accessories

Compatible Accessories BASE KICKSTAND 500 ADULT 26-28 (Model Code 8302792) BASE AND SEAT KICKSTAND 520 CN (Model Code 8401256) SEAT POST CARRIER 500 (Model Code 8387783) 300 BIKE 24" - 28" MUDGUARD KIT (Model Code 8328053) ST MUDGUARD SET CN (Model Code 8550005) FLASH MTB FRONT MUDGUARD - BLACK (Model Code 8327776) BABY SEAT 100 FRAME (Model Code 8486913)

User guide & bike assembly

Learn more



Storage instructions

After washing, rub with a dry cloth to remove all traces of moisture. Store your bike in a cool, dry place, away from corrosive products and salty air.


Lifetime on frame and rigid fork. 2 years on parts.

Superior quality. Unbeatable prices.

For 40 years, Decathlon has delivered the best value in the retail sports industry by offering high-quality, sustainable and cost-effective products.

Decathlon makes the difference
  1. product-research

    Research and development

    delivers high-quality cost-effective products

  2. State-of-the-art production processes

    minimize manufacturing costs

  3. Optimized supply chain

    reduces retail prices