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Nukeproof Reactor 290 Carbon ST review

An exciting all-rounder with a penchant for descending

Our rating 
4.0 out of 5 star rating 4.0
GBP £4,700.00 RRP | USD $4,700.00 | AUD $6,600.00
Pack shot of the Nukeproof Reactor ST full suspension mountain bike

Our review

The Reactor ST isn't as fast as some uphill, but it’s a proper demon when pointed back down
Pros: Surefooted downhill demon; great spec at a reasonable price; good geometry and ride position
Cons: Easy going but not as efficient as some uphill; only slightly lighter than the top-spec Reactor which has more travel and a burlier build
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Nukeproof’s approach to creating a short-travel trail/downcountry bike is a little different to some of the bigger brands.


While the likes of Specialized and Cannondale use their cross-country thoroughbreds as the foundation for their equivalents – upping travel, tweaking geometry and adding burlier parts – Nukeproof comes at it from the opposite direction.

The Reactor ST is based on the Reactor, Nukeproof’s do-it-all trail bike. But will this approach pay off on the trails?

Nukeproof Reactor Carbon 290 ST frame and suspension details

To create the Reactor ST, Nukeproof took its proven trail bike, the Reactor, and pared it back in a bid to inject a little more efficiency without losing its core handling characteristics.

It wasn’t a case of simply bolting a host of lighter parts to the trail bike frame, though. The full-carbon Reactor ST frame pumps out 125mm of rear-wheel travel, reduced from 130mm on the standard Reactor (using a shorter stroke shock), and is designed to work with a 130mm rather than 150mm travel fork.

That rear wheel travel is delivered by Nukeproof’s ‘Swinglink’ driven four-bar Horst Link suspension platform and controlled using a highly adjustable Fox Factory DPS rear shock.

Nukeproof uses Enduro MAX bearings for all of the pivots on the Reactor ST and sells replacement bearing kits at £29.99, for when the time comes for a freshen up.

Cables are all routed internally and the bottom bracket is threaded. There’s plenty of rubberised frame protection to help ward off rock strikes or keep the chain rattle to a minimum.

The maximum tyre size at the rear is a generous 2.6in wide.

While Nukeproof offers the Reactor in both alloy or carbon and with 29in or 650b wheels, the Reactor ST is only available with 29in wheels and in carbon. Sizing ranges from medium to extra-large.

Pack shot of the Nukeproof Reactor ST full suspension mountain bike
The Reactor ST is available in alloy with 29in or 650b wheels, and in carbon with 29in wheels.
Steve Behr / Immediate Media

Nukeproof Reactor Carbon 290 ST geometry

Due to that reduction in front and rear travel when compared to the standard Reactor, the ST’s geometry is a little less extreme, though it’s still progressive compared to a number of other bikes with similar intentions.

Two ovalised chips sit at the top of the seatstays and attach to the swing-link that drives the shock. These can be flipped between ‘trail’ and ‘rail’ modes to adjust geometry, changing the head and seat angle by 0.5 degrees and the bottom bracket by 6mm.

In trail mode, my test bike’s head angle measured 66 degrees – slacker than stated on Nukeproof’s geometry chart – and the seat angle sat at a steep 76.2 degrees.

The 460mm reach on my medium offers a roomy, surefooted stance on the bike when up out of the saddle, while the 440mm chainstays balance stability and agility nicely.

When seated, the effective top tube on the size medium is 608mm. This is paired with a 50mm stem.

At 330mm, the Reactor ST’s bottom bracket height is the closest to the ground of all the bikes I had on test, and nearer still in rail mode.

Seat angle - actual (degrees)71.871.871.8
Seat angle - effective (degrees)76.376.376.3
Head angle (degrees)66.866.866.8
Chainstay (cm)444444
Seat tube (cm)4245.850.8
Top tube (cm)60.863.867.3
Head tube (cm)10.51111.5
Fork offset (cm)
Bottom bracket drop (cm)
Bottom bracket height (cm)333333
Wheelbase (mm)1,1981,2281,264
Standover (cm)7373.876.3
Stack (cm)60.861.461.8
Reach (cm)4648.852.16

Nukeproof Reactor Carbon 290 ST specifications

Considering its kit and compared to the other similarly equipped bikes, the Reactor’s price is really quite impressive.

The 130mm travel Fox Factory 34 fork (with 44mm offset) uses the highly adjustable GRIP2 damper. It works well with the DPS shock at the rear, which has a blue lever to toggle between open, medium and firm modes, plus a winged, three-position black dial below tunes the feel of open mode.

Shimano’s XT 12-speed drivetrain continues to impress with precise shifting and reliability. Nukeproof has specced the two-piston Shimano XT brakes, rather than the four-pot version, but they still manage to pack a considerable punch – the 180mm rear rotor helps here, rather than the smaller 160mm rotors typically found on a lot of bikes in this genre.

DT Swiss XR 1700 Spline alloy wheels are wrapped in 2.3in wide Maxxis rubber. Up front sits a Minion DHF while at the rear is an Agressor – both use the 3C MaxxTerra rubber compound.

Nukeproof supplies its own carbon bar, stem, grips and saddle, and it’s all really good, well-made kit that’s easy to get along with.

With no pedals, the Reactor ST in size medium weighed 13.65kg.

Nukeproof Reactor Carbon 290 ST ride impressions

Male cyclist in blue top riding the Nukeproof Reactor ST full suspension mountain bike
Some of the bike’s downhill swagger comes from the well-proportioned frame, with numbers that equate to stability and a BB height that elevates confidence and lets you rail turns.
Steve Behr / Immediate Media

A lot is expected of a downcountry-style bike – it needs to be very capable uphill, great at covering ground quickly but still able to more than hold its own going downhill – so I tested the Reactor ST on a wide variety of terrain and in a number of different conditions.

Initial testing took place on a natural singletrack loop featuring tight uphill switchbacks and climbs riddled with roots. While the descents weren’t the steepest, there were plenty of roots to contend with, so the bike needed to carry speed well to keep the trail flowing.

Other testing including trail centre laps where the terrain may have been more sedate, but speeds were generally higher and the ground surface was consistently rough.

I also ventured onto some steeper sections of downhill trail to push this bike to its limit and see just how capable (or not) it was.

Set up was very straightforward. Once I’d set the sag, aside from backing off the low- and high-speed compression damping on the fork, I didn’t need to touch the fork after that.

At the rear, with the shock in open mode, I used the firmer of the three open-mode settings. It took some time experimenting to get to this, but I found the bike worked well enough on the climbs and on the flat, without any compromise when descending.

Nukeproof Reactor Carbon 290 ST climbing performance

The Reactor ST’s steep seat angle is instantly noticeable and helps sit you in a very comfortable position when climbing.

While it’s not as stretched out as bikes at the XC end of the spectrum, it still feels roomy enough. It was only when navigating some really awkward uphill, root-covered turns that I had to shuffle slightly further forward on the saddle to help keep the front end down. That’s partly down to how the Reactor ST sits down into its travel, effectively slackening the seat angle, but I still cleaned the climbs without too much bother.

Stand up out of the saddle and lay the power down and the Reactor ST feels energetic enough

While it’ll squat and bob a little under power, stay seated and spin at a steady cadence and the Reactor ST feels reasonably efficient and climbs well. On longer drags, I did find myself reaching for the shock’s lever to firm the back end up a bit though.

Stand up out of the saddle and lay the power down and the Reactor ST feels energetic enough. Power delivery isn’t as urgent as Transition’s Spur, but it doesn’t hang around when you really start mashing at the pedals.

Although the tyres roll pretty well, this particular combo is notably knobblier and grippier than you’ll find on other similar bikes.

Combine that with close to 2kg extra weight compared to the likes of Cannondale’s Scalpel SE LTD, Specialized’s Epic EVO Expert and Transition’s Spur X01, the Reactor ST needs a bit more grunt at times. But considering that this bike is £1,300 cheaper than the Spur X01, for example, it’s more than forgivable.

Nukeproof Reactor Carbon 290 ST descending performance

Although the Reactor ST might not be quite as athletic as some when pointed uphill, it’s trail bike genetics make it more of a menace when pointed downhill.

For a start, both tyres offer decent levels of traction through the turns, with prominent shoulder treads that are more than happy digging into soft soil.

The Agressor out back does clog quite quickly in really gloopy mud but still manages to be decently grippy when it counts and handles wet roots and rocks in a more steadfast fashion than more XC-focused rubber.

While it’s not the lightest bike in the category, it’s easy to chuck around the trail thanks to the support through the suspension

Some of the Reactor ST’s downhill swagger also comes from the well-proportioned frame, with numbers that equate to stability and its corner-railing bottom bracket height really helps to elevate confidence when things start getting more involved.

Both tyres boast formidable shoulder treads that really dig in once the bike has been banked over, while that low-slung underbelly and confident stance on the bike let you grapple for tricky lines or carve through the inside of a turn without hesitation.

While it’s not the lightest bike in the category, it’s easy to chuck around the trail thanks to the support through the suspension. The Fox 34 fork feels well-controlled and more than precise enough for this type of bike.

At the rear, you’d be fooled into thinking there’s more than 125mm of travel at your disposal from the DPS. Its supple initial touch helps when it comes to maintaining traction on loose surfaces yet there’s support when needed, to load the bike through turns and enough ramp-up at the end of the stroke to deal with some seriously big hits. This is both a good and bad thing.

On the one hand, it makes you want to ride the Reactor ST even harder, but you can soon start pushing it beyond its comfort zone and into longer-travel trail bike territory. You do start to wonder, considering the small weight difference between this and the longer travel Reactor RS: “would the full-blown Reactor be just as good an all-rounder as this?”

Downhill expectations might be lower if the Reactor ST was a little lighter and a touch more efficient, maybe? Perhaps we could see Nukeproof creating a lighter, more bespoke frame for this category in the future, which would be great.

Either way, while the Reactor ST can’t quite match the pace uphill as the best in category, you simply can’t ignore how fun, playful and fast it is to ride back down the hill.

Nukeproof Reactor Carbon 290 ST bottom line

The Reactor ST is a really capable and immensely fun bike to ride. It’s not as energetic when pointed uphill as the likes of the Transition Spur, which has just 5mm less travel, and on long drags it’s worth locking the shock out to help keep things feeling that bit more efficient.

When it comes to riding back down, this is one seriously fun bike that’s more than happy being popped, bounced and lofted from line to line. However, it isn’t quite as well-rounded as the very best in the category, which feel like they’re balancing compromises just a bit better than the Reactor ST.


I’m being incredibly picky, but that’s what it comes down to with bikes as good as this. And this is a really good bike for the money.

How we tested

We put four of the best downcountry mountain bikes through their paces on a range of terrain, which they are designed to handle – including trail centre laps, flowing bike park style descents and jumps, natural singletrack, technical climbs as well as steep, bump-riddled descents – to find out what this burgeoning category of bike is all about.

But what does downcountry mean? Imagine a bike that can tackle all-day epics with speed and efficiency, covering ground with an ease that even a well-put-together trail bike would struggle to muster.

What’s more, not only can it eat up the miles, but it’s designed in such a way and has the right mix of parts to handle rugged natural singletrack or the odd flowing jump trail with more stability than its limited travel might suggest.

Suspension travel generally sits between 110 and 125mm, and they’re fitted with relatively light, fast-rolling tyres on 29in wheels. Dropper posts tend to feature too, for maximum trail flow.

Due to current availability issues, the bikes in our test are top-end builds, or close to it, but if you can’t stretch to these lofty price tags there are cheaper models available in most cases – although you may face a wait for one.

Also on test

Product Specifications


Price AUD $6600.00GBP £4700.00USD $4700.00
Weight 13.65kg (M) – without pedals
Brand Nukeproof


Available sizes M, L, XL
Headset Nukeproof
Tyres Maxxis Minion DHF 3C MaxxTerra EXO 29x2.3in (fr), Maxxis Agressor EXO 29x2.3in (r)
Stem Nukeproof Horizon, 50mm
Shifter Shimano XT M8100
Seatpost Bikeyoke Divine with Shimano remote, 160mm
Saddle Nukeproof Horizon SL
Rear Shocks Fox Factory Float DPS
Rear derailleur Shimano XT M8100
Handlebar Nukeproof Horizon Carbon V2, 780mm
Bottom bracket Shimano XT
Grips/Tape Nukeproof Sam Hill Signature
Frame Carbon, 125mm (4.9in) travel
Fork Fox Factory 34 GRIP2, 130mm (5.1in) travel
Cranks Shimano XT M8100
Chain Shimano XT M8100
Cassette Shimano XT M8100
Brakes Shimano XT M8100 (180mm rotors)
Wheels DT Swiss XR1700 Spline 25 rims on DT Swiss 350 hubs