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Rockrider ST100, Mountain Bike, 20'', Kids 3'11" to 4'5"

Sale price: $150.00 Regular price: $249.00

A sturdy, single-speed, 20" white bike that's simple to ride. Equipped with a bell, it can be ridden around town as well as on trails.

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Sale price: $150.00 Regular price: $249.00

Free shipping over $35

Final Sale: No returns or exchanges

Free returns

Free pickup

San Francisco, 735 Market St. Options

Select an available color and size to see options.

Model: 8549158

Product Features

A photo of the Rockrider ST100, Mountain Bike, 20'', Kids 3'11" to 4'5" in use

Rockrider ST100, Mountain Bike, 20'', Kids 3'11" to 4'5" | Designed for 6 to 8 year old children who are beginning to learn to ride a bike.

A sturdy, single-speed, 20" white bike that's simple to ride. Equipped with a bell, it can be ridden around town as well as on trails.

Easy to learn

Single-speed, simple and efficient bike. Bike weight 24.3 lbs.

Bike safety

V-Brakes provide powerful and easy braking.

Lifetime warranty

B’Twin offers a lifetime warranty on the frame, stem, handlebar and rigid fork.

Product Customer Reviews

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36 Reviews
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Rockrider ST100, Mountain Bike, 20'', Kids 3'11
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Great quality product!!!

Santa brought my son this bike for Christmas. My son was not an experienced rider, but this bike has brought out his confidence and love for biking. Now looking at adult versions for my wife and I. I highly recommend this product and I plan on this being the first place I look for bikes in the future.

Want to love it as much as my grandsons do

I ordered two of these bikes for my grandsons for Christmas. They are beautiful (the bikes and the grandsons). However, one of the bike's inner tubes will not air up and the front breaks on that same bike will not adjust properly. The other bike is in perfect working order. I really wish they were both in that condition so both of my grandsons were happy.

Thank you for sharing your feedback on our Bike.

I am sorry to read your bad experience with one of the bike received. It clearly seems that the inner tube is defective and that the brake needs adjustment. Despite our quality checks in production, I would like to apologize for this unconvenience. I have asked our customer service to be in contact with you and I sincerely hope we will find a solution to make sure your grandsons enjoy their bikes and the lifetime warranty that comes with it on the frames.


Olivier WTYKLO - Cycling Department

At 100

I bought this bike for my grandson. Bike came by mail 90% assembled. My grandson liked it very much. The rear tire keep losing air. We are keeping an eye on that. It looks like some kind of leak.

Great bike for kids!

This bike is great! Simple for my son to work the brakes. Great quality. Super easy to put together. Customer service is also fantastic.

Best Kid's Mountain Bike

Satisfied with this product.

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Hello and good day to you Mr Zairul Hezry,

We at Decathlon Shah Alam are delighted to hear that you are satisfied and happy with your purchase of the Rockrider ST100 Kid's 20" Moutain Bike. Friendly reminder that we offer 6 months FREE service, 2 years warranty for the entire bike, and lifetime warranty for the stem; handlebars; rigid fork; and frame (excluding all wear and tear).

We hope to see you soon whether it be here at Decathlon Shah Alam or any other of our branches and offer you the best of service. For any inquiries please feel free to contact us at 03-55243599 .

Thank you immensely,


Wheels Sports

Wan Ammar
Great Bike Kids (Beginner)

Rockrider ST100 bike is sturdy with easy adjustable seat that's comfortable and suitable for my kids (ages 9-11) who just started to learn cycling without the supporting wheels. They pickup cycling less than 15minutes :)

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Dear Mahzura, thank you for your time in leaving us with a 5-Star rating on our product/service. We are glad that we managed to delight you with the standards of our product/service. We really appreciate your loyalty with Decathlon. Please let us know if there is anything else we can improve on in the future. Thank you once again for your time and we hope to serve you again soon!

Mohd azman
20’’ Bicycle

Need to check on this as front wheel seems to be loose.

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Dear Mr. Mohsin,

thank you for taking the time to write the review! We are truly sorry to hear that our product and service did not meet your expectations. We have read your feedback and will take note of these points into improving ourselves to better satisfy your needs. Thank you once again for your time and we hope to serve you again soon!

Khairil Hafiq

Kids' Mountain Bike RR 20" ST 100 B'TWIN

my son loves it

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Excellent price and service

I went to Decathlon to buy a bike for my 8 y.o. son. without any particular preference other than to get an affordable solution. Once in the store, I was pointed to the bike I ended up buying. The staff advised me on size, which I would have possibly guessed wrong, and price. This was the last piece in the store at the lowest price. They set up everything very quickly and I left the store quite satisfied with the bike and the service.

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Product review

Quite a comfy bike for kid

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The Chain Is Too Loose

The Chain Will Come Out Many Times A Day, Very Frustrated

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Hi Patrick,

Thanks for taking the time to leave a review of the ST 100 RR 20 inch Kids Bike! I'm sorry to hear about your difficulty with the chain coming off.

It sounds like the locknuts for the rear wheel may have worked loose and thus there is not enough tension to keep the chain on the sprocket or chainring.

Our Workshop Leaders will be more than happy to help you sort it out - you will just need to make an online booking here.

I will feed back to our Cycling and/or Production teammates about this - please rest assured that we take such feedback seriously and will work to improve our processes in the future. Thanks and have a great day!


Digital Sport Leader

Cycling & Roller Sports


my 7 year old son's first bike. he likes it.

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Kids' Mountain Bike

My daughter enjoys cycling on this bike so far

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kids bicycle

good, the kids love it

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Additional Product Information


Bike frame

  • 100% Steel


The chainwheel anti-derailment device and low step-through frame make it easy to get on and off.

Accessories / equipment

Fully equipped for use on public roads (bell, reflectors). The rear derailleur guard protects the derailleur from damage in the event of an impact.



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

  4. laptop-checkout

    Minimal retail footprint

    lowers overhead and indirect costs