At road.cc every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.
Good scores are more common than bad, because fortunately good products are more common than bad.
Merlin Cycles has been offering its own brand of bikes for a while, and the Nitro SL is an excellent addition thanks to its balance of speed, light weight and comfort. A lot of companies get slated for rebadging off-the-shelf carbon fibre models but Merlin has chosen well with this Belgian beauty.
It's no secret that Merlin has opted for Ridley's Helium SL frameset as its base for the Nitro SL. With the Helium SL being upgraded to the SLX, the Nitro SL could be considered outdated tech, but it is far from it.
The frameset holds its head up high and delivers across the board against the competition.
The ride is sublime, that balance of stiffness and the way it deals with the bumps in the road is a masterclass in carbon fibre layup and tube design. The Nitro SL just seems to take everything in its stride with regard to road surface imperfections.
At 7.7kg, a smidge under 17lb if you're that way inclined, the Merlin is light and very responsive. It climbs way better than you'd expect and acceleration is very impressive thanks to that very stiff bottom bracket area.
The whole package works so well together that even though you could save a chunk of weight with a carbon wheel upgrade, one that the Nitro SL would relish, as a straight-out-of-the-box setup the Merlin is hard to knock.
Even though the Nitro SL is a race machine with its 1:41 stack to reach ratio (stack and reach are the vertical and horizontal measurements from the centre of the bottom bracket to the top of the head tube) plus aggressive seat and head tube angles, its handling is a little less direct than you'd expect. It lacks that real razor sharpness of a lot of peloton-ready frames when things get really technical in the bends, but this does mean that it makes for a great long-distance bike.
When fatigue kicks in, for instance on an all-day training ride or when pushing yourself on a challenging sportive, a twitchy handling bike becomes more of a chore than a benefit.
That isn't to say the Merlin is the soft option – the whole thing is pretty rigid, and thanks to the tapered head tube things are tight up the front end when it comes to steering or heavy braking.
The biggest highlight for me was the way that the Merlin just got on with the job. There doesn't seem to be a compromise with its performance: you get on it, pedal like a mad man, and it delivers. You'll be amazed by how much ground you'll cover with relatively little in the way of effort.
The Nitro SL comes adorned with a UCI approved sticker, which means you can ride this bike in any of the governing body's sanctioned events should you so wish. All of this is because just 12 months ago this frame was being powered by the legs of the pros – not something you'd normally expect for less than two grand.
With a claimed frame weight of just 750g, the Nitro SL frame is up there with the lightest, and just shows how far you could go with the build; full Di2 and some super duper lightweight carbon rims for instance wouldn't embarrass this frame in feel or looks.
Manufactured from 24/30 ton carbon fibre, a figure related to the tensile strength of the fibres, the various tube profiles make for a very stiff frame. As I mentioned earlier, you get a tapered head tube for stiffness plus the down tube has a square section, oversized profile to tame the forces at both ends.
With all the woes of press fit bottom brackets and their creaking issues because of poor tolerances, it's good to see Merlin has opted for a threaded bottom bracket setup. Okay, you sacrifice a small amount of rigidity by going narrower at the BB, but unless you're riding two differing frames side by side it's difficult to detect.
The chainstays aren't the largest we've seen, but again they deliver what they need to, while the seatstays are narrow for some shock absorption. It all works together, as the Merlin delivers both in out-of-the-saddle sprints and those seated, dig-in, get-it-done efforts.
In terms of cabling, the gears run internally through the frame, which means both electronic and wired groupsets will work without spoiling the lines. The brake cables run on the outside and, to be honest, are barely noticeable.
One good thing to note is the inclusion of a replaceable dropout on the drive side; it's quite commonplace these days, and it's always good to know you won't write off an entire frame from a small crash.
The Nitro SL comes with a full Shimano Ultegra 6800 groupset, which is about right for this price point, but it is good to see Merlin hasn't scrimped anywhere by subbing out the crankset or brakes to another manufacturer.
The setup we've got here is a 52/36 semi-compact chainset which, when paired with the 11-28t, 11-speed cassette, gives a sporty range of gears ideal for this style of bike.
Ultegra's shifting is top notch, being only slightly less precise than Dura-Ace for a fraction of the price, and the braking power from the callipers is massively efficient in all but the wettest of conditions. The Ultegra slate finish also matches the frameset's paintjob too. Nice.
Fulcrum's Quattro LG is a decent wheelset too, specced off the shelf with 35mm deep alloy rims and a solid build. They roll really well and even with their claimed 1,725g weight they don't feel sluggish on a bike of this calibre. They'll take a huge amount of abuse, so I'd say they are only worth upgrading if you want to really go for the ultimate weight saver build
The same could be said for the tyres. Continental's Ultra Sports are far from the grippiest or most supple of rubber but they do the job and offer plenty of durability too.
4ZA is Ridley's in-house brand and features here as the bar, stem and seatpost. They're all alloy, but they do the job and to upgrade them would only really be a vanity exercise. The compact drop of the bar will suit most, offering plenty of hand positions.
There are a lot of Ultegra-equipped carbon fibre bikes out there for less than the two grand rrp of the Nitro SL, but this one has pedigree. It's pro-level peloton-proven, and while the badge snobs may struggle to agree, it's one hell of an accomplished frameset.
There are others out there mind: the Canyon Ultimate CF SL 9.0 for instance, which when you add on postage and packaging comes in at £1,945 with a very similar build.
But, get this, at the moment Merlin is offering the Nitro SL for £1,749.95 and that includes a set of pedals – Ultegra for instance – plus a pair of Mavic Ksyrium Ultimate II shoes, which range from £90 to £120ish on t'internet. The Merlin looks like a bit of a steal.
The Nitro SL uses a race-proven formula, offering speed and long-distance comfort
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road.cc test report
Make and model: Merlin Nitro SL
Size tested: 54cm
About the bike
State the frame and fork material and method of construction. List the components used to build up the bike.
Frame: 24 Ton High Modulus Carbon
Fork: Carbon Blades with Carbon Steerer
Wheels: Fulcrum Racing Quattro LG wheelset
Tyres: Continental Ultra Sport II 25mm folding bead
Chainset: Shimano Ultegra 6800 52/36T
Front Derailleur: Shimano Ultegra 6800 or Di2
Rear Derailleur: Shimano Ultegra 6800 or Di2
Gear/Brake Levers: Shimano Ultegra 6800 or Di2
Brake calipers: Shimano Ultegra 6800
Cassette: Shimano 105 5800
Handlebars: 4ZA Stratos
Stem: 4ZA Stratos
Seatpost: 4ZA Stratos
Saddle: San Marco Ponza
Weight: 7.70kg (Medium)
Maxium Rider Weight: 95kg
Tell us what the bike is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about the bike?
Merlin says: "Superlight race bike weighing a helium light 7.70kg. The oversized tube shape is engineered with the use of extremely high modulus carbon. This results in a very light frame, without compromising stiffness. The dual purpose internal cable routing uses the same holes for mechanical and electronic shifting, resulting in a very clean design. Flex seat stays increase vertical compliance for additional comfort, without reducing lateral stiffness.
"This is without a doubt our best looking Merlin road bike, coupled up with the bomb proof Shimano Ultegra 6800 11 speed group and Fulcrum's Racing Quattro Wheels make this an epic value for money top racer! 4ZA take care of the rest of the finishing kit with components from their Stratos range."
The Merlin Nitro SL is a pro-level-proven frame and it is impressive to ride.
Frame and fork
Tell us about the materials used in the frame and fork?
The Merlin is constructed from 24 ton high modulus carbon fibre and includes a full carbon fibre fork, aluminium dropouts aside.
Tell us about the geometry of the frame and fork?
Full details are here: https://www.merlincycles.com/resources/images/Merlin%20Nitro%20SL_GEO_ne...
Things are pretty aggressive, as you'd expect from a full-on race bike.
How was the bike in terms of height and reach? How did it compare to other bikes of the same stated size?
Stack of 545mm and reach of 385mm is pretty typical for a bike in a 54cm size, and the ratio of 1:41 is what you'd expect for a race bike.
Riding the bike
Was the bike comfortable to ride? Tell us how you felt about the ride quality.
Yes, supremely so.
Did the bike feel stiff in the right places? Did any part of the bike feel too stiff or too flexible?
Yes, it delivers on all levels without being overly harsh.
How did the bike transfer power? Did it feel efficient?
Power transfer is impressive throughout the frame.
Was there any toe-clip overlap with the front wheel? If so, was it a problem?
Yes, but no real issue.
How would you describe the steering? Was it lively, neutral or unresponsive? The lively side of neutral.
Tell us some more about the handling. How did the bike feel overall? Did it do particular things well or badly?
The handling is quick without being overly twitchy. I've ridden more 'point and shoot' kind of bikes but the Merlin doesn't lack precision.
Which components had the most effect (good or bad) on the bike's comfort? would you recommend any changes?
It is a good all-round package that works together.
Which components had the most effect (good or bad) on the bike's stiffness? would you recommend any changes?
I liked the 4ZA components as they didn't offer any flex.
Which components had the most effect (good or bad) on the bike's efficiency? would you recommend any changes?
You get a little bit of an aero boost from the Fulcrum wheels.
Tell us some more about the drivetrain. Anything you particularly did or didn't like? Any components which didn't work well together?
Shimano Ultegra 6800 delivers its usual ratio of performance versus price.
Wheels and tyres
Tell us some more about the wheels.Did they work well in the conditions you encountered? Would you change the wheels? If so, what for?
The Quattro LG wheels are solid while offering a decent aero boost thanks to their depth. Swapping them out for some truly lightweight wheels will give the Merlin a massive boost.
Tell us some more about the tyres. Did they work well in the conditions you encountered? Would you change the tyres? If so, what for?
Continental's Ultra Sport tyres are decent performers, but if you really like to push a bike's handling limits then an upgrade would be welcome.
Tell us some more about the controls. Any particularly good or bad components? How would the controls work for larger or smaller riders?
The 4ZA components are Ridley's in-house brand and they are decent quality components without being anything flash. They are spot on for the price.
Did you enjoy riding the bike? Yes
Would you consider buying the bike? Yes
Would you recommend the bike to a friend? Yes
Use this box to explain your score
Merlin has played a blinder here, offering a race-proven frame at such a great price. Yes, two grand is still a lot of money for a bike, but it delivers on every level, especially for those who want to travel a large distance at speed, in comfort.
About the tester
I usually ride: This month's test bike My best bike is: Kinesis Aithien
I've been riding for: 10-20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: time trialling, commuting, club rides, sportives, fixed/singlespeed
With 20 years of road cycling and over 150,000 miles in his legs it's safe to say Stu is happiest when on the bike whatever the weather. Since writing his first review for road.cc back in 2009 he has also had a career in engineering including 3D-CAD design and product development, so has a real passion for all of the latest technology coming through in the industry but is also a sucker for a classic steel frame, skinny tyres, rim brakes and a damn good paintjob.
His fascination with gravel bikes is getting out of control too!