Review: Trek Fuel EX Jr

28 September 2015

Trek’s new Fuel EX Jr is a quality, full-suspension junior MTB. Does it justify its big price tag?

And what difference does a full-sus bike make to a skilled young mountain biker anyway? We took it to the Olympic MTB venue to find out.


Trek Fuel EX Jr




13.0 kg / 28.6 lbs (without pedals)


Trek Bicycle –


1. About the Bike

A specialist children’s bike of this value is never going to be sold in high volumes, so we’re pleased to see a global manufacturer like Trek extending its kids’ range with a serious full-sus model.

Trek has taken the best features of its renowned Fuel EX trail bike (such as its sophisticated rear suspension) and applied them for the first time to a children’s MTB. Trek markets the Fuel EX Jr as suiting kids from 1.38m to 1.52m tall – that’s about the height of a nine to twelve year old (depending on the size of the individual child of course).

At £1400, you’re unlikely to confuse the Trek with the dozens of super-heavy, very cheap MTB-styled children’s bikes from supermarkets. Those are marketed as full-sus but their crude suspension is almost completely ineffective, and they’re not suited for serious off-road use.

With its glowing green frame and its quality components the Fuel EX Jr looks fabulous from the moment you set eyes on it. Whenever we parked the bike it drew a lot of attention – it’s one of those bikes that kids really want to ride.


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2. About our Test

By testing the new Trek we were keen to judge three things:-

  1. Has Trek understood the specific needs of highly capable youth riders?
  2. How does the Fuel EX Jr perform when ridden hard?
  3. Is it worth a skilled young mountain biker riding a full-sus bike anyway instead of a hardtail?

To carry out most of the testing we made a pilgrimage to Hadleigh Park in Essex, home of mountain biking at the London 2012 Olympics. With 1.7km of climb per 5km lap, the Olympic course has plenty of sharp descents, climbs and pretty challenging technical features that are ideal for testing a full-sus bike. We tested the bike in the venue’s skills area and on its pump track too.

Our 12-year-old tester is one of the most experienced & successful youth MTB riders in his region, with dozens of races and hundreds of trail rides in his legs already. So that you can get an idea of the bike’s proportions from our photos, you should know that he is approximately 1.50m tall and weighs around 37kg. He’s used to racing on top-quality hardtails that have been prepared well, and he was itching to ride a full-sus bike hard.

Hadleigh Park’s trails are mainly man-made from crushed sandstone, but we also tested the bike on grass and mud. The weather was wet during most of our test rides.

We ran the bike in completely standard spec as supplied by Trek. The only changes we made were: fitting the tester’s own pedals; adjusting bars, saddle & controls to suit the tester; and setting the tyre pressures appropriately for the test rider & the terrain.

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3. Geometry and Bike Fit

This is an area that most manufacturers still get wrong for junior MTBs – they often struggle with integrating suspension components into very small bikes and they still don’t always get the basics of proportional components right – i.e. crank length, bar width, saddle size, controls.

Although nearly all adult MTBs have moved up from 26” wheels to 27.5” or 29”, Trek has sensibly designed the Fuel EX Jr around 26” wheels: they’re in better proportion to the rest of the bike and to the size of the rider; they help to achieve a good riding position; and they’re more nimble for a small rider to handle. The bike’s proportions make it look like a scaled down 29er, in fact.

The bike’s 12.5” frame certainly looks super-compact with its rear shock and suspension components squeezed into it. Despite all that hardware needing space, Trek has still managed to design the frame with a very low standover height, and there’s plenty of room for the rider to move the bike around beneath them when riding extreme technical features.

The front of the bike has been kept low enough for a small rider by using a short 95mm head tube and forks with 90mm travel, as well as using 26” wheels.

The lengths of the bike’s frame and its handlebar stem give a reach to the bars which is just right for a bike of this size.

Usefully for small riders, the bottom bracket height is a couple of centimetres lower than that of the full-size adult Fuel EX bikes too.

The handlebars are 580mm wide and the junior saddle is 240mm long – both correctly sized for small riders.

The brake levers are reach adjustable to match small hands.

After being previously disappointed by the long cranks fitted to Trek’s KRX junior cyclocross bike we were pleased to see that the cranks were 160mm long on their Fuel EX Jr – just about right for the bike’s size of rider.

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4. Weight

After lifting up a good hardtail MTB of similar size like the Islabikes Creig 26 (10.5 kg / 23.1 lbs) there’s no doubt that the Trek does feel heavy at 13.0 kg / 28.6 lbs. There’s simply a lot more material in a full-sus MTB than in a hardtail, but the Fuel EX Jr’s weight is still pretty competitive with small-sized adult full-sus bikes of similar value.

Like most off-the-peg bikes, the ticket-price is kept down by the manufacturer specifying cheaper, relatively heavy wheels as standard, assuming that a keen owner will upgrade them before too long. And that’s the case with this Trek too: there’s almost a kilogramme to be saved here if you want. That would make a big difference to the bike’s agility too.

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5. Frame and Forks

This is where most of the bike’s value is focused (in fact, Trek sells the frame & forks alone for £1100, although you’d surely be better off buying the whole bike). The frame is a neatly scaled-down version of the full-size aluminium Fuel EX, with the same clever design and construction.


Trek is proud of its work to engineer rear suspension which works properly for such small riders – simply reducing the shock’s air pressure doesn’t give the right results.


The X-Fusion Microlite RL rear shock is a very compact unit that suits the bike’s character. It has several adjustments to match the rider’s weight, riding style and terrain, although it was already set up well on the test bike. The rear shock is integrated with Trek’s Full Floater, Evo Link and ABP suspension components. Trek describes the bike’s various frame and suspension features in detail, and you can read about them here.


Front suspension is handled by an X-Fusion Velvet RL air sprung fork with rebound adjustment and lockout. There’s only 90mm of suspension travel, but that’s plenty for a versatile bike like this which is designed to be ridden by a small rider over a variety of terrain.

Adding a dropper seatpost would make the bike even more versatile and effective on technical downhills, but the frame’s short, curved seatpost wouldn’t let you do that. You could always add a quick-release seatpost bolt as a simple alternative though.

The fork has Trek’s E2 steerer – that means it is a chunky 1 1/2” in diameter at the bottom of the tube, tapering to 1 1/8” at the top. A tapered steerer tube is intended to be stronger and lighter than a standard steerer.


The  frame is well-constructed and finished in gloriously bright “Volt Green” – the same colour that Trek’s full-size £3000 Fuel EX 9 is painted. Every kid who saw the bike loved its styling and colour.

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6. Wheels and Tyres

Bike manufacturers tend to specify relatively basic wheels so that a bike can be kept down to its target price point. Trek has fitted straightforward wheels with basic hubs from the popular Taiwanese brand Formula, laced with 32 spokes to double-walled Bontrager AT-650 rims. Note that both hubs use 9mm bolt-on axles rather than quick-release axles.

Trek’s in-house brand Bontrager also supplies the versatile XR2 tyres. These 26×2.2” tyres are good all-rounders and they always gripped well during testing. Our rider had a high level of confidence in them.

But if you have any cash remaining after buying the bike itself, upgrading to a pair of lightweight tubeless wheels and tyres would certainly improve the bike’s performance. However, being 26” it’s unlikely can you buy finasteride online that you’d also have a use for them on a larger sized bike when your child outgrows the Fuel EX Jr, as they’d almost certainly move up to a 27.5” wheel bike.


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7. Drivetrain

There are plenty of quality Shimano Deore 10-speed components bolted to the Fuel EX Jr – the front derailleur, rear derailleur, and shifters. The cassette is a Shimano HG50 with 11 to 36 teeth.

The Deore Shadow Plus rear derailleur is a great component for a bike like this which is likely to be hammered down rocky descents. The clutch-style design helps to prevent a dropped chain and reduces “chain slap”.


The 160mm crank is from Prowheel, another Taiwanese super-producer of bike components often used on junior bikes. It’s a decent quality unit fitted with sensible double rings of 32 and 24 teeth. That gives a great range of gears from 24×36 to 32×11 – low enough for very steep climbs and high enough for long straight descents. However, we think a 1×10 drivetrain would have been ideal – simpler to operate and lighter weight than the double chainset fitted.


Sensibly for a bike that’s designed to ride technical trails fast, there’s a bashguard fitted too – especially as the bottom bracket is 20mm lower than on the equivalent adult-sized bike.

The transmission changed gear faultlessly and worked smoothly in all of our test situations.

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8. Brakes

Trek has specified Shimano M355 hydraulic disc brakes. That’s a typical spec on a full-sus bike of this price, and the brakes have a good reputation for reliability and control.

As you’d expect, there’s no lack of braking power since the bike is being ridden by such light riders. Brake lever reach adjustment allows you to keep the braking performance under proper control.


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9. Components

Like most Trek bikes, the Fuel EX Jr is finished with components from its own Bontrager range. There’s a good junior-sized saddle, and we were pleased to see that the alloy seatpost has a two-bolt saddle clamp – more secure and easier to adjust finely than a single-bolt clamp.


The Bontrager handlebars are just the right size and shape for the bike’s purpose and the rider’s size. They have a classic design with a gentle rise, and their 580mm width matches the narrower shoulders and riding position of a child.

There’s a quality Bontrager Elite 7 stem which is nice and short (65 mm) for quick handling and good control.


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10. Performance

The best person by far to write about the bike’s performance is its test rider Alex:-

The riding position felt comfortable and the bike is very well balanced. I really like the full suspension although a hardtail would be quicker on an XC course.

There’s very little sag when climbing even when the suspension isn’t locked out. The bike made light work of the technical descents, soaking up the rough terrain and even the larger rock drop-offs. The cables might need to be re-routed though because my knees knocked them when I was climbing.

We asked Alex whether he was particularly conscious of the Fuel EX Jr’s extra weight compared to the lightweight all-carbon Giant hardtail that he normally rides. He didn’t find it a big problem though, and it was balanced out by the extra capability of a full suspension bike.

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11. Customisation and Upgrade

If you have any spare cash after splashing out on the bike itself, the first place to invest it is in a pair of lighter wheels and tubeless tyres. That would make a big difference to the bike’s performance, especially handling and climbing.

Beyond a wheel upgrade, there’s really nothing else that makes sense to upgrade. You could tinker with the spec by fitting a lighter seatpost, stem or bars, but you’d hardly notice the difference.

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12. Service and Support

Trek is a huge brand that sells through a national network of retailers. The Fuel EX Jr is a specialist, low-sales volume bike, though, so don’t expect every Trek dealer to have one in stock. They can all supply it easily though.

Trek’s customer service and warranty are top notch, so you and your dealer should have no issues getting any problems resolved or obtaining replacement parts.

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13. Value For Money and Resale

There’s no doubt that £1400 is a lot more money than the vast majority of parents and kids would be prepared to spend on a children’s bike. But the Trek isn’t intended for the majority – it’s for a small number of people in very specific circumstances.

For example, it’s at its best in the hands of fit, highly-skilled kids who confidently ride fast over black routes at the most challenging trail centres. Those kind of riders would already have developed the skills to ride the toughest technical features on a hardtail, but they’ll descend even more quickly and have even more fun on a full-sus bike. Test rider Alex would have liked to take the Trek to Coed y Brenin, for example, where he thought the bike would fly.

The price £1400 is roughly equivalent to the cost of an adult bike of similar spec, so Trek doesn’t seem to have loaded the price particularly just because the bike is manufactured in much lower volumes.

What’s the competition for the Fuel EX Jr? In fact, the bike has almost no junior 26” wheel full-sus direct rivals. There are a few well-specified hardtails which are lighter and cheaper, particularly the excellent Islabikes Creig 26 (although right now this isn’t currently available in the UK, only in the USA at $1200).

Alternatively, if your child is at the upper end of the Trek’s size range and you can find a quality full-sus XXS adult frame for 26” wheels (i.e. that’s likely to be two or three years old, before most MTBs moved to 27.5” and 29” standard sizes) then you could consider building up your own high-spec junior MTB.

However, there are quite a few 24” wheel ful-sus junior MTBs of similar price and quality to choose from though, especially if you’re prepared to order direct from the USA where they are more popular. Some of these lean towards a more Downhill design & specification than the versatile trail/XC-oriented Fuel EX Jr.

Although these bikes have smaller wheels than the Trek, the frame size and other dimensions are often similar so they do fit the same size riders in fact. There’s no doubt that a 26” wheel bike will roll faster and ride more smoothly than the 24” wheel bikes though. Check out these competitors:-

  • Norco Fluid (£1049). The 24” wheel version is certainly available in the UK but we think the 26” wheel version might be US-only.
  • Specialized offers its Camber Grom ($2200) in the US only too. Unusually, this is supplied with 24” wheels but is designed to accept 26” wheels too, making it a direct competitor to the Trek.
  • Kona’s Stinky 24 (£1499) is widely available in the UK.
  • US brand Lilshredder offers its very pricy Phenom 24 ($3000+) which is built to order using your chosen specification.
  • The Commencal Supreme 24 (£1400) is more Downhill oriented than the Trek but of similar quality.
  • Lapierre sells the Froggy 24 (£1550) in the UK.
  • Mondraker’s Factor 24 (£1900) is a high spec bike with an expensive price-tag.

The resale value of the Fuel EX Jr is hard to predict. However, if you’re the kind of family which is into MTB in a big way you’ll probably also have plenty of contact with other parents of highly skilled kids. So, providing the bike has been well looked after, you’ll probably find it easy to sell the bike when your own child has out-grown it.

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14. Verdict

There’s no doubt that Trek has built a terrific little MTB which is very well sorted. The designers have clearly stayed focused on the needs of young riders, and they haven’t committed any of the design & specification sins that we often see in junior bikes from big brands.

The bike is high quality throughout, and at £1400 it’s actually fair value. But you’ll probably only be seriously considering the Fuel EX Jr if you’re the kind of family that lives & breathes mountain biking, which has highly skilled kids, and which spends all of its time riding the most exciting trails together.

If that sounds like you, then the Trek Fuel EX Jr lets your kids enjoy the same standard of bike that you do.

+ design and specification
+ proportional sizing
+ quality
+ performance
– weight of wheels
– 2×10 drivetrain instead of 1×10



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4 responses to:

Review: Trek Fuel EX Jr

  1. September 28, 2015

    A great review! I totally agree that a 1×10 set-up would be ideal, indeed it would be ideal for most kids MTBs. Front mech shifting on a MTB can be hard for small hands, and most kids keep the chain on the same ring no mater what. The problem is finding the right 1×10 gear ratio. The smallest narrow/wide chainring you can get is a 30 tooth. Matched to a stock 11-36 cassette, that gives a 30×36 lowest gear. Quite a bit higher than the 24×36 of the stock set-up. The only way to get an equivalent lower gear is to fit an a 42 tooth cassette extender, and most (all?) manufacturers won’t go to the trouble speccing that. Its a problem… I’ve kept my kids on doubles at the moment just to let them have the lower range, though I am going to try a cassette extender.

  2. Youth Cycle Sport
    September 28, 2015

    Thanks for your comment. Wolftooth, Blackspire and one or two others supply narrow/wide chainrings down to 26t and 28t for 4-arm MTB cranks with small BCD (e.g. 74, 76, 80mm). So I guess you (or Trek!) could go down that route to create a nice set of 1×10 ratios.

  3. September 28, 2015

    Oooo. Didn’t know they went down that small. Much better being able to go smaller on the chainring, than having to pay extra for an XT cassette and the extender, and then potentially wear it out and replace it.

  4. Esteban Silva
    January 24, 2016

    Because of the fact that 26 inch full-suspension bikes are becoming rarer, I was having a horrible time finding a bike for my wife, who is 1.47 m tall and weighs 36 kilos. Her main problem is finding a bike with a low enough standover.
    So, we ordered one of these at our LBS, sight unseen, after poring over the specs. The shop guys were skeptical, trying to put her on an “adult” bike. We insisted, and my wife couldn’t be happier! The Fuel Jr. has given her more confidence and control than on her hardtail.
    The bike, and especially the wheels, is really very heavy, and it seems to me Trek should offer something lighter (even at a higher cost), as for a child the time window to use the bike is limited. You don’t want to shell out an extra chunk of money so that a 30 kilo child can handle the bike a bit better.

    Anyway, it’s most definitely a 5-star bike!! congratulations Trek!

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