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Rockrider ST900, Mountain Bike, 24", Kids 4'5" to 4'11"

Sale price: $349.00 Regular price: $449.00

THE 24" mountain bike. Aluminum frame, 6 speeds, trigger shifters, suspension fork and disc brakes; everything your child needs for a sporty, comfortable ride!

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Sale price: $349.00 Regular price: $449.00

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San Francisco, 735 Market St. Options

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Model: 8659410

Product Features

A photo of the Rockrider ST900, Mountain Bike, 24", Kids 4'5" to 4'11" in use

Rockrider ST900, Mountain Bike, 24", Kids 4'5" to 4'11" | 8-12-year-old children (4'7" - 5'3")

THE 24" mountain bike. Aluminum frame, 6 speeds, trigger shifters, suspension fork and disc brakes; everything your child needs for a sporty, comfortable ride!

Easy to use

Alu frame, 6 speeds, trigger shifters,quick-release with front and rear wheel

Bike safety

Disc brakes, knobbly tires, derailleur guard, and Aheadset stem.

Cycling comfort

suspension fork

Product Lifestyle Image Gallery

Image Gallery

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24 

Rockrider ST900, Mountain Bike, 24

Product Customer Reviews

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Rockrider ST900, Mountain Bike, 24
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Great bike

Great bike

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Bought for my 9 year old son and he thinks it’s absolutely brilliant. The bike has some great features and looks the business. You get a lot of bike for your money.

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Grandson new bike

Lovely bike great value

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Child's bike fault

Bike gear lever not returning to allow gears to be operated fully despite a pre delivery inspection. Had a two hour round journey to collect the bike and another two hour round trip to return the bike the next day. Gear lever mechanism had to be stripped and freed off to allow operation. I just can't understand how this could have been missed during a pdi especially on a child's bike where safety is paramount.. The bike it's self is really nice and looks great so I would recommend this model.

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Quality components, assembled without due care

The bike is fine. The quality of the assembly was rubbish. Rear derailleur not properly set up, necessitating a trip back to the store the next day for it to be resolved. Not informed about the 3-month check either, despite it saying on the form I had been. My confidence that this bike has been properly assembled was therefore pretty low, and to top it off I was accused by the mechanic of having damaged it! Sad to say I am pretty unlikely to buy any more bikes from Decathlon as a result.

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Great bike. Was worth paying the little more for a better bike. My son loves it.

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My little boy advanced his riding skills so quickly on this bike, it was just perfect for him. He is a tall 7 year old and this was his first bike with gears, they were so easy to use he took to it straight away.

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This bike is the business!

Bought this bike for my 9 year olds birthday. Wanted a lighter weight bike for him. It is extremely well made. It helps that it is checked over by the Decathlon staff which is a bonus. The great thing about this bike is the disc brakes. These will give my son extra confidence when riding.

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Great bike for my 9 years old

Great value as always, disc brake and nice quality bike.

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He loves it

Bought for christmas and my son (6yrs) absolutely loves his new bike, top of his christmas presents! Set up by the team at Decathlon Gateshead, it's been stored until Christmas Eve, and he launched himself at it on the big day. Within an hour of being awake, he was outside. First bike with gears, gripshift makes this so easy for him, the size is perfect and he was off zooming up and down the street with ease. The next day, we went out further, confident and riding well, the bike handles the riding. Next, we'll be hitting the trails.

Rockrider, 24in Wheels,

Great bike for the price, sadly I think the chain is too short, will pop in in Jan to sort it.

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Click and collect

We where met with very friendly staff and given great service. My grandson will enjoy his Christmas present

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Rockrider ST

Bought as a Christmas present for my son, delivered fast with minimal assembly, it’s a great quality bike. expect to pay twice as much from a high street bike shop ! Spot on Decathlon

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It’s good, but not great.

First off, I went to pick the bike up. I turned up at the store to find it had already been built. I was not made aware of this as I wanted to build it with my son himself, plus, it would have been much easier to transport and wrap for Christmas. Decathlon, you need to give people the choice. So that aside, it’s not a bad bike. Looks nice, although the frame design is a little dated and the head angle could do with being a bit slacker. It mentions in the advert that it has oversize handlebars. They’re really not oversize at all, they are 2cm wide than my sons current 20 inch wheel bike. This bike could do with around 580mm bars at the minimum. Grips are OK but quite smooth so will be terrible when wet. Tyres are a hard compound, so they’ll likely last a while, but grip wise they’ll not be great. They could also do with being 2.1 wide rather than 1.95 which looks quite skinny on a bike of this size. Brakes are budget, but do a decent enough job of stopping. I don’t see them lasting too long though due to the quality. It shifts quite nicely to be fair, and has actual thumb shifters rather then those horrible twist shifters you see on most kids bike, so it’s a thumbs up for that. This bike would benefit from a smaller chainring though to give more climbing power. Weight? Well, they advertise 12kg, it’s more like 12.5 on the scales I used. Still light though and I’ll lose half a kg just upgrading the heavy tyres. Suspension is where I was most disappointed to begin with. OK, I expect cheap spring forks, but I expect them to actually work. They were very stiff, almost like they were getting stuck on the stanchion covers. I ended up having to service the forks (completely take them apart) and lube the stanchion covers along with all moving parts. Now that has been done they are a lot smoother, but should have been like that in the first place. Upgrade the tyres and bars, service the forks and you’ll be fine.

Brilliant bike

Brilliant bike for my son we went on a 10 mile bike ride tonight I must point out yes the stores first day back open was today and as expected it was busy outside and inside what I'm concerned for is the staff especially in the warrington store where I was I could here a few of them talking saying they had not stopped for a break I hope this gets sorted asap as the staff in that store are very good at there job and helpful having them disposals masks on for me was not ideal in the heat but that's upto you good luck good store.

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Size Guide

Size Guide Visual

Additional Product Information


Bike frame

  • 100% Aluminium 6061


Made out of aluminum for a lightweight frame. The Aheadset stem makes maintenance easy and makes the frame more sturdy for riding on any kind of terrain. Its rear S-bend stays optimize braking performance and make it easier to get through mud.


Suspension fork to dampen vibrations from rough and rugged paths or terrain.


Change gears (6 speeds) using trigger shifters (on the handlebar).


Mechanical front and rear disc brakes for powerful, precise braking. Braking power is not affected by mud or bumps.

Handlebars / stem / steering

Suspension fork dampens vibrations on rough terrain for added comfort and better control. The Aheadset stem provides additional safety during all-terrain cycling.

Wheels / tires

Stronger, double-wall rims give the bike a resolutely sporty look.




Lifetime (frame, stem, handlebars). Details on Availability of spare parts: 2 years

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