BTWIN 20” EXPL 900R review: Budget kids mountain bike
When we first saw the BTWIN 20” EXPL 900R, we were intrigued to see whether this budget-friendly 20 inch kids’ mountain bike could live up to the excellent standard we’ve come to expect from other bikes in the BTWIN range. Could it inspire confidence in our young tester and help him continue his off-road progression?
In this review, we take a close look at how the bike has performed over 18 months, from first impressions to long rides, trail centre adventures, and everyday family cycling.
Disclosure: Cycle Sprog were sent the BTWIN 20” EXPL 900R to review. We were not paid to write this review, and all opinions are our own. We do use affiliate links, so may get a small commission if you choose to buy through the links on this page. This funds the website, and we thank you for your support.
BTWIN 20” EXPL 900R bike key data:
Price - £329.99
Weight - 9.9kg
Height range - 120-135cm
Inside leg range - Not stated
Age range - 6-9 years (dependent on height)
Colours - Red
Date of review - October 2025
Pros - Budget-friendly, good components for the price point and durable design.
Cons - Not super lightweight and the gear shifters may be a little tricky for the smallest hands.
BTWIN 20” EXPL 900R bike scores
Quality - 4/5 - A quality budget-friendly kids' mountain bike.
Weight- 4/5 - Not the lightest, but our reviewer grew in confidence riding it, and this weight is to be expected for the price tag.
Value for money - 5/5 - Great spec, design and durability for a budget-friendly price point.
Customisability - 5/5 - Decathlon stocks all the accessories that you'll need for this bike. Including water bottles, mudguards and mountain biking clothing.
Resale value - 3/5- BTWIN is a well-known budget brand; it won't get a super high resale value as it was cheaper to start off with, but Decathlon's buy-back scheme will make the upgrade to your child's next bike more affordable.
Final verdict - The BTWIN 20” EXPL 900R is an excellent, budget-friendly mountain bike and all-around bike for your adventurous child to grow in skill and confidence on.
Find out more about the Cycle Sprog review process
About our reviewer
In just 18 months, the Rockrider has taken Rowan from a slightly wobbly rider who preferred smooth tarmac to a confident blue trail shredder.
Rowan was five when he started using the Decathlon MTB, and at nearly seven, he’s still riding it, with room to grow for at least another year. In that time, his skills and confidence have flourished, supported every step of the way by this bike.
When he first ventured off-road, Rowan wasn’t keen on bumpy terrain or loose surfaces. But with a no-pressure approach, he’s now found his way to enjoying himself on trails. Watching older riders tackle technical sections and having a bike that looks like theirs has given him belief in his own ability.
As a family, we tend to ride a mix of longer outings on quiet roads, gravel tracks and cycle paths, as well as shorter play sessions in the woods. Rowan is now confidently developing his mountain bike skills and tackling blue routes at trail centres such as Whinlatter Forest Park, Grizedale Forest and Glentress Forest, leading and following Mum and Dad through the trails, both of whom are keen cyclists.
BTWIN bikes: Brand overview
BTWIN is Decathlon’s in-house cycling brand, known for producing well-designed, affordable bikes for riders of all ages. Their kids’ bike range is structured into three tiers:
- 100 Series: entry-level, heavier bikes with basic components, ideal for short rides on smooth surfaces.
- 500 Series: lighter and better equipped, perfect for children gaining confidence and tackling more varied terrain.
- 900 Series- the lightest and best-equipped in the line-up, offering excellent handling and performance at a competitive price point.
The BTWIN 20” EXPL 900R sits in the top-tier 900 range, making it a fantastic choice for young riders ready to explore further and ride with confidence.
We’ve previously reviewed several BTWIN bikes, including the Riverside 900, the 16” Discover model and a baby balance bike, and they’ve consistently impressed us with their performance and value.
You can read our full BTWIN kids’ bike range guide here: BTWIN Kids Bikes – A Comprehensive Range Overview.
First impressions of the BTWIN 20” EXPL 900R
Rowan’s first reaction of the BTWIN 20” EXPL 900R was pure enthusiasm; this looked like a “real” grown-up bike, complete with gears and a bottle cage mount (kids love being able to carry their own water!). The bike is well-proportioned and solidly built. Wide handlebars offer positive control and a balanced riding position, while chunky tyres and a sloping downtube give it the unmistakable look of a proper mountain bike.
As parents, we agreed with him, it looks like a serious bit of kit. The gear range is generous, and he was excited to have gears to tackle hillier terrain on family rides after growing out of his single-speed 18” hybrid bike.
Assembly was straightforward, requiring only standard Allen keys (provided) and basic bike knowledge.
The wheels feature quick-release levers, which is useful as Rowan’s bikes get bigger and we need to remove wheels for transport.
A quick-release seat post makes height adjustments simple as well, and is particularly handy on downhills.
This feels like a well-built, practical kids’ mountain bike, not a toy, which shows in its capability off-road. Rowan also firmly believes that red is the fastest bike colour!
BTWIN 20” EXPL 900R specifications
On the scales, the BTWIN 20” EXPL 900R weighs 9.98 kg. When Rowan started riding it, that was about half his body weight, dropping to around a third by the end of the test period.
Proportionally, it’s the equivalent of an adult riding a 30 kg bike that gradually becomes 20 kg. This made the bike feel lighter as he grew, and he never struggled to handle it.
He can nearly lift the bike himself, with size, not weight, being the only limiting factor. 9.98kg is heavier than lightweight hybrid bikes, which Rowan was moving from, but a pretty standard weight for budget and mid-range mountain bikes.
The bike has rigid forks rather than heavy, ineffective suspension forks often found on budget MTBs. Instead, its large-volume tyres (2.2 inch) do the work of smoothing out trails.
It’s equipped with mechanical disc brakes for powerful stopping, and an 8-speed thumb trigger gear shifter that makes climbing easier.
The 140 mm cranks are a thoughtful touch for little legs, making pedalling easy, while the geometry is designed for off-road trail riding to inspire confidence. Wide handlebars increase stability and control.
The disc brakes performed well and were easy to use. The levers are long and span the bars. Initially, Rowan had to move his whole hand from the bar to reach the brakes, but as his hands and confidence have grown, he now covers the brakes with a couple of fingers off-road with ease.
The brakes are strong and offer smooth, predictable stopping, helping him learn proper braking technique and modulation.
The gear shifters have large plus and minus symbols, which made teaching him how to use them straightforward. The gears shift smoothly and Rowan has developed a solid understanding of when to shift and which lever to use over the testing period.
At first, when Rowan was at the smaller end of the recommended size, the longer lever throw for easier gears was a big stretch for small hands. We remind him to change down early, as sometimes, especially when he was less confident shifting gears, he doesn't manage to push it all the way and then needs to stop to get into an easier gear.
This is our main negative of the bike, as little hands need super-easy gear shifting, especially when they are learning about gears for the first time.
This was Rowan’s first geared bike, and he was proud to have something like Mum and Dad’s.
The EXPL 900R’s 8-speed cassette gives a good spread for both on- and off-road riding. The lowest gears helped him conquer short 10% gradients, and although he spun out at top speed on the flat and downhills, that’s perfectly appropriate for his age and size.
The saddle and pedals are well-suited to a child’s mountain bike. Rowan had no complaints, even on long rides, and the pedals offer a wide, stable platform. His feet have occasionally slipped, but he’s learned to recover without stopping.
We’ve considered upgrading to grippier pedals but will wait until his skills are more advanced, as grippier, spiky pedals alongside clumsy riding often result in very sore shins!
The tyres have performed well in wet, muddy and rooty conditions, with minimal wear and no punctures despite plenty of mixed-surface miles.
Running them at low pressures adds comfort and grip without the need for heavy suspension.
Riding the BTWIN 20” EXPL 900R
This bike has handled everything we’ve thrown at it, long road and gravel rides, family commutes, forest play sessions, and trail centre adventures.
Rowan has ridden green and blue routes at trail centres, played in the woods, and even tried a tow rope on longer hills to stretch his range.
Since getting this bike, our family rides have grown longer, and Rowan has pushed himself more.
He’s ridden to school, cycled alongside lochs in Scotland, explored bomb-holes in the local woods and taken on trail centres and bike parks.
His longest ride has been around 12 miles on the road without any issues.
He also brought the bike along to Ard Rock Enduro, where he spent hours happily cruising around the campsite with a pack of other kids, inspired by the pump track.
The BTWIN 20” EXPL 900R has been a brilliant first mountain bike, handling challenging terrain while helping Rowan develop his braking and gear-shifting skills.
We’ve yet to find its limits, and there’s still seat post extension left to grow.
Aside from adding a bottle cage, we’ve made no modifications.
After 18 months of testing and plenty of rough use, the components are holding up brilliantly, the paint remains bright, and there’s no sign of rust or significant wear.
Thoughts from the Sprog
When we told Rowan that it was time to return the BTWIN 20” EXPL 900R loan bike, he was genuinely disappointed and immediately asked if we could buy the exact same model.
He says the bike is fast, he loves the gears, and he thinks it looks brilliant. He’s proud to ride it, and that says a lot.
Overall verdict of the BTWIN 20” EXPL 900R
Young children benefit from having one really good bike that can do everything. A versatile, capable bike means their progress isn’t held back, and they can explore all kinds of riding as their confidence grows.
The BTWIN 20” EXPL 900R delivers on this. It’s solid, practical, confidence-inspiring, and great value for money. Over the 18 months we’ve ridden it, Rowan’s skills, love of cycling and stamina have grown significantly. Even on tough days, he never blamed the bike, it’s always performed exactly as expected.
We’ve had no issues with any of the components, and the frame has only picked up a few small scratches despite plenty of off-road adventures. There’s still life left in it for at least another year, and we’re confident it could be passed on to another child once Rowan outgrows it or gain a good buy-back price from Decathlon’s buy-back scheme.
We’ll be buying one ourselves to replace the review bike, and that’s probably the biggest endorsement we can give.
Other articles you may be interested in:
- Mountain biking with kids
- Gravel cycling with kids
- How to clean a kids bike
- Best pump tracks for kids
- How we became a mountain biking family in just one year
- How to stop your kid getting saddle sore: a guide to kids bike saddles
- Best 20″ kids mountain bikes for 5-6 year olds
- Best 24″ kids mountain bikes for age 7-10 years
- Best 26″ mountain bikes for kids
- Best mountain bikes for teenagers and small adults
- Best kids’ full-suspension mountain bikes
Comments