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Merida Reacto 4000 review

A pro bike ride experience in a much more affordable package

Our rating 
4.5 out of 5 star rating 4.5
GBP £2,250.00 RRP | AUD $3,499.00
Pack shot of the Merida Reacto 4000 road bike

Our review

The Reacto is a star performer on the road and it’s good enough to justify big upgrades down the line
Pros: Superbike-like ride; ultra-modern design; clean cockpit
Cons: Better wheels and tyres would really let it shine
Skip to view product specifications

The Merida Reacto is a full-on aero race bike, a slippery sibling to the all-rounder Scultura, and the more comfort-focused Scultura Endurance.

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The Shimano 105-equipped Reacto 4000 is the cheapest model in the range but it shares key features with the flagship Reacto Team-E superbike.

We previously tested the mid-level Reacto 6000 with Ultegra and found it to be a brilliant bike despite its weight and relatively pedestrian wheels and tyres.

The Reacto 4000 is lower specced again and cheaper by a healthy margin, but it retains the key qualities that make the Reacto such a compelling platform.

Merida Reacto 4000 frameset

The Reacto 4000’s CF3-designated carbon frameset is identical in shape to the more costly CF5 of the flagship builds. That means you get exactly the same aero benefits and clearance for 30mm tyres, not to mention identical ride quality and stiffness according to Merida.

The more affordable frame weighs a claimed 1,165g plus 490g for the fork, a penalty of around 200g over the CF5 – small beans in the scheme of things.

The Reacto is a handsome bike with a finish that looks decidedly premium. The black parts of the frameset have a matt finish, while the red portion and logos are glossy, and it’s all very neatly executed.

Merida Expert CC saddle houses a multi-tool for mechanicals.
Merida’s saddle houses a multi-tool for mechanicals.
Russell Burton / Immediate Media

The Reacto’s frameset embodies all the current trends in aero road bike design, with a near-horizontal top tube, truncated aerofoil tube profiles and very dropped seatstays. It looks purposeful, but not like it’s trying too hard.

The Reacto’s cables are almost entirely hidden from view and at the cockpit end of things, Merida has opted for FSA’s SMR cable routing system, as seen on a number of other machines including the Bianchi Arcadex gravel bike.

This is a nice halfway-house between the complex proprietary systems found on many of the latest superbikes, and a conventional setup with the cables on show.

The stem, bar and fork steerer are all standard sized parts so third-party components will fit. The cables run underneath the stem and into the front of the headset, and are concealed by a cover and the dedicated headset spacers.

This results in a very clean front end but the cables are easily accessed if need be, and swapping stems is straightforward. Replacing the upper headset bearing will mean disconnecting cables and hoses, however.

Shimano 105 hydraulic disc brakes on the Merida Reacto 4000 road bike have cooling fins
Heat sink cooling fins for the Reacto’s braking.
Russell Burton / Immediate Media

Merida has been sticking heatsinks on its disc brake caliper mounts for years and the Reacto is no exception here. I’m pleased to note they’re rather tidy on this bike though, and tucked well out of the way.

On the Scultura Endurance, by contrast, the rear heatsink can catch your foot if, like me, you have a slightly heels-in pedalling style. One of my shoes still bears the scars.

Merida Reacto 4000 build

Apart from the KMC chain, the Reacto 4000 has a full Shimano 105 hydraulic disc groupset. The gearing is racy, with a 52/36 crank, but the 11-30 cassette means your bottom end is still reasonably low.

Better yet, Merida specs a GS – Shimano’s designation for medium-cage – rear derailleur, so there won’t be any issue fitting a bigger cassette should the need arise.

The wheels are own-brand 30mm-deep rims on slightly nondescript hubs. The rims’ internal width of 19mm is well-suited to road tyres and the rims can be converted to tubeless, although neither tape nor valves are provided.

If inner tubes don’t do it for you anymore, you’ll need new rubber though because the Merida has specced rather budget-oriented Continental Ultra Sport III clincher tyres.

That FSA stem aside, the Reacto’s finishing kit is all in-house too, and there’s nothing to fault.

The Merida Team CW seatpost on the Merida Reacto 4000 has an integrated rear light
The aero post has an integrated rear light.
Russell Burton / Immediate Media

The dedicated aero seatpost has a substantial cut-out just below its head to add compliance. This is filled in with a neat rear light – a nice touch because it means you’ll never be without one.

It’s not ultra-bright, but it’s certainly better than nothing and, as it runs on a triple-A batteries, it’s not going to be rendered useless by a failing built-in battery in a couple of years.

The Merida saddle has a trick of its own in the form of a neat multi-tool tucked under its tail, a nice little bonus that’s genuinely useful.

At 8.7kg (including that light and multi-tool, I should note), the Reacto 4000 sounds relatively heavy, but it’s not unusual for its class. Between disc brakes and aero frames, we’ve got used to mid-range road bikes being a little heavier and, as we’ll get onto, the Reacto is really none the worse for it.

Merida Reacto 4000 geometry

Seat angle (degrees)74.5747473.57373
Head angle (degrees)70.57272.573.573.574
Chainstay (mm)408408408408408408
Seat tube (mm)470500520540560590
Top tube (mm)520536545560575590
Head tube (mm)105112128140155176
Bottom bracket drop (mm)707066666666
Wheelbase (mm)9859839909909991,010
Standover (mm)746771792810826853
Stack (mm)517529542557571593
Reach (mm)377384390395400409

Merida Reacto 4000 ride impressions

For a bike with a mid-range groupset and fairly basic wheels, the Reacto 4000 does a more than passable imitation of a superbike.

It’s stiff, fast and fun, with a ride that feels distinctly more refined and comfortable than you might assume – aero bikes have come a long way since the genre really took off.

The Reacto’s geometry is quite racy and it’s worth noting that sizing runs big – my medium test bike has 395mm of reach and 557mm of stack, numbers that would make it a size large (or 56) for many brands.

The angles are race-bike steep and the wheelbase is short at 990mm – all pretty standard stuff that produces a quick-handling, lively feeling ride.

Shimano 105 drivetrain on the Merida Reacto 4000 road bike
Shimano’s ever-reliable 105 drivetrain.
Russell Burton / Immediate Media

You can’t feel incremental aero gains and you can feel weight, but the Reacto is a joy to ride regardless, the sort of bike that rewards hard efforts and gives you that fizzy feeling that you’re riding something a little bit special.

There’s no question that better wheels and premium tyres would unlock extra sparkle, but the standard components don’t manage to dull an exciting ride. Round bits aside, the build is solid too – Shimano 105 is as competent as ever and it looks good with it.

Merida Reacto 4000 overall

Along with Giant, Merida is a brand that’s relatively generous with its detuned models. The differences between the big money flagship and the entry-level model are smaller than they might be elsewhere and if you do buy into the bottom of the range, you’re getting a bike that’s ripe for future upgrades when budget allows.

From a purely aesthetic perspective, there’s always something slightly out-of-kilter about an aero bike with relatively low-profile rims.

To my mind, the Reacto 4000 is crying out for deep sections; a set of 50mm or deeper carbon clinchers would turn a handsome bike into a properly mean-looking one and, along with better tyres, they would unlock a little extra potential.

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Even in standard form, however, the Reacto is a genuinely excellent bike.

Product Specifications


Price br_price, 5, 3, Price, AUD $3499.00GBP £2250.00
Weight br_weight, 5, 6, Weight, 8.7kg (M), Array, kg
Brand br_brand, 5, 10, Brand, Merida


Available sizes br_availableSizes, 11, 0, Available sizes, XXS, XS, S, M, L, XL
Bottom bracket br_bottomBracket, 11, 0, Bottom bracket, Shimano BB86 press-fit
Brakes br_brakes, 11, 0, Brakes, Shimano 105 hydraulic disc
Cassette br_cassette, 11, 0, Cassette, Shimano 105 11-30
Chain br_chain, 11, 0, Chain, KMC X11
Cranks br_cranks, 11, 0, Cranks, Shimano 105 52/36
Fork br_fork, 11, 0, Fork, Reacto CF5 IV Disc
Frame br_frame, 11, 0, Frame, Reacto CF3 carbon
Front derailleur br_frontDerailleur, 11, 0, Front derailleur, Shimano 105
Handlebar br_handlebar, 11, 0, Handlebar, Merida Expert CW 420mm
Headset br_headset, 11, 0, Headset, FSA ACR
Rear derailleur br_rearDerailleur, 11, 0, Rear derailleur, Shimano 105
Saddle br_saddle, 11, 0, Saddle, Merida Expert CC
Seatpost br_seatpost, 11, 0, Seatpost, Merida Team CW
Shifter br_shifter, 11, 0, Shifter, Shimano 105
Stem br_stem, 11, 0, Stem, FSA SMR ACR 110mm
Tyres br_tyres, 11, 0, Tyres, Continental Ultra Sport III 25mm
Wheels br_wheels, 11, 0, Wheels, Merida Expert CW