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Best of the best: Cyclist’s favourite lightweight bikes

8 Dec 2020

A great climber’s bike needs to be a lot more than simply lightweight. Cyclist’s expert testers choose their favourites

Photography: Mike Massaro

Back in the early 1900s the idea of a bike weighing less than 15kg was a pipe dream. But by the 1960s a skinny steel racer could comfortably hit 10kg, and with a little help from ‘drillium’ – the fad that saw mechanics and riders drill holes in brake levers and chainrings to shave grams – even lighter.

Eddy Merckx’s Hour Record bike of 1972, built (and drilled) by Ernesto Colnago, weighed just 5.75kg, and even De Rosa’s heart logo was a result of weight saving, with Ugo De Rosa drilling three holes into a bottom bracket shell then cutting a triangle between them to lose excess material.

Aluminium followed steel, with Italian manufacturer Alan creating the original mass-production aluminium frame, which weighed as little as 1.6kg, in 1972. A few years later titanium joined the party, among the first the 1974 Teledyne Titan whose 2kg frame was a third lighter than comparable steel.

And then carbon fibre came along and started chipping away, bike by bike, at weight targets once thought impossible to reach.

The biggest target was the UCI weight limit of 6.8kg, which might have seemed optimistically low when it was introduced in 2000 but is now embarrassingly outdated. As early as 2004 Canyon engineer Hans Christian Smolik created the experimental Projekt 3.7, a 3.7kg, 16-gear bike.

In 2006 the Germans were at it again, debuting the Projekt 6.8, a 6.8kg disc brake road bike. In fact weight seems a bit of a theme in Germany, with the record for the lightest rideable bike standing at 2.7kg – a custom project started by German Gunter Mai, then finished off by Jason Woznick of Fairwheel Bikes in Tucson, Arizona.

As for production – ie, not custom – bikes, the feathery crown rests with German brand AX Lightness, whose Vial Evo Ultra tips the scales at 4.4kg thanks in part to a frame weighing under 600g. Most recently Specialized has hit the headlines with its Aethos (see p13), a sub-6kg fully built racer that the company claims has the lightest disc-frame ever built – just 585g for a size 56cm.

It’s incredible stuff, but there is a big but. When we put together the list of our favourite lightweight bikes it soon became clear that weight wouldn’t actually be the defining factor. Otherwise a bike such as the Tifosi Mons, which stole 15 minutes of fame by dressing up in the most expensive parts and weighing a claimed 4.6kg, would be on the list.

Not that it’s a bad bike, but it is an example of how if you throw enough money at a light-ish frame (780g) you can hit crazy-light numbers – 790g AX Lightness tubular wheels anyone? That isn’t really cricket.

No, bike design has come so far that at the top end riders can and should expect a more holistic approach, such that stiffness, comfort and even aerodynamics need not be sacrificed.

Weight matters and it underpins our choices here, but there’s much more to these bikes than meets the scales.

For a guide to the best road bikes money can buy, click here 
To see Cyclist's pick of the best aero bikes, click here

Specialized Tarmac SL7

As chosen by editor-at-large Stu Bowers

Read Stu's full review of the Specialized S-Works Tarmac SL7 here

Can a bike be an icon of a sport the way an athlete can? I don’t see why not, in which case the Tarmac is that icon. It’s the Eddy Merckx of bikes – the most successful of all time – having won World Championships, Olympic titles, Spring Classics, Grand Tours… it’s hard to find a race the Tarmac hasn’t excelled in. But there is a common denominator behind much of its success: weight.

The Tarmac has always been Specialized’s lightest, an accomplished all-rounder but one that shines brightest when the road points up. It’s the bike the pros reach for when there’s a summit finish or indeed any big climb. But despite such success Specialized hasn’t always gotten things spot on.

The Tarmac family is so venerable it can trace its roots back nearly two decades, the 2002 aluminium Tarmac E5 chalking up wins under Mario Cipollini before the full-carbon models found favour with Tom Boonen.

Yet since then it has been through a number of revisions, some good, some not so good (here’s looking at you, weird-handling SL2 and annoying-proprietary-wheelset SL5) before arriving at this, the Tarmac SL7. And this time around it’s outstanding.

The key difference here is that Specialized has used the very latest computer modelling techniques and its in-house wind-tunnel to merge the aero performance of its Venge into the Tarmac’s characteristics – cue wide, deep Roval wheels, dropped seatstays and fully integrated cables, all wrapped up in a 6.8kg package (S-Works size 56cm). Its frame weighs less than 800g including paint and hardware, making it one of the first lightweight bikes slippery enough to earn the tag ‘aero-road’.

To flesh that out with some numbers, Specialized says the Tarmac SL7 is 45 seconds faster over a 40km time-trial than the previous SL6 and loses just 2.5W in drag – mere seconds – to the current Venge.


Under normal circumstances I’d almost certainly have had the chance to take the SL7 to the mountains to test it in its natural habitat, but as it was launched amid a global pandemic testing has been restricted to my local routes. That hasn’t stopped me from getting a true sense of this bike’s capabilities.

I’ve ridden almost every version of both the Tarmac and the Venge in the past, and while each new bike generally felt like a general improvement, the Tarmac SL7 feels like it has invented its own category.

I don’t say that lightly. This bike’s predecessor, the SL6, was a standout bike that all in the Cyclist office agreed was one of best disc bikes of 2018/19. So too the latest Venge, which is a superbly fast bike that also manages to be decently light at 7.1kg.

And yet the Tarmac SL7 eclipses them both, in the Venge’s case so much so that the manufacturer has now officially withdrawn the bike from its range (albeit it will continue to produce the frameset for the time being). A lightweight bike killing off its aero sibling? Even just six months ago that would have been unthinkable.

This is why the Tarmac SL7 makes the cut here. It is light enough to be a true climber’s bike yet it could also lay claim to being one of the best-handling bikes on the market. It delivers an electrifying sense of power transfer on climbs, which combined with its low weight means it launches into attacks and accelerates with ease, eating up the road on steep gradients.

Beyond that it is also extremely agile, with a stable and unfaltering demeanour on descents and a road-hugging stance in corners. Then there’s the speed it can hold on flat and rolling terrain – the aero credentials make themselves well known.

If there’s a chink in this bike’s armour I haven’t been able to find it. It’s not even uncomfortable. Tot these things up and this bike proves that we no longer have to accept compromises in handling, stiffness and comfort if we want to go fast uphill or down.

The race to the Holy Grail, that magical triumvirate of low weight, aerodynamics and amenable ride feel, I think is over. I can’t help but wonder how long it will be before other brands start to combine their superbikes in a similar way. 

Learn more about the Tarmac SL7 from Specialized here.

Factor O2 VAM

As chosen by tech editor Sam Challis

Read Sam's full review of the Factor O2 Vam here.

A dusting on the scales must be supported by capability on the road, which is why the O2 VAM made its mark on me. With the frameset coming in under a kilo thanks to a frame weighing a claimed 667g (54cm), a top-end build hovers around 6.6kg.

That’s a disc brake bike coming in 200g under the UCI weight limit, using components that are top-spec but ultimately conventional.

Despite the bike’s skinny silhouette, features such as the ‘wide stance’ seatstays and sculpted bottom bracket junction mean the O2 VAM is stiff enough at the rear for sprint efforts – and that’s coming from an 84kg rider.

Combined with its low weight and disc brakes, that rigidity makes for a brilliantly reactive bike that accelerates and brakes with pleasing promptness. Few bikes have allowed me to dart around the technical Dorset lanes I ride on with the same level of confidence. Firing into turns and powering out of them is consistently rewarding.

The VAM is comfortable and handles well too. The lightest carbon fibres are by definition the stiffest, so to roll around and not have my fillings shaken out, or to find the bike doesn’t hop around like popcorn kernels in a microwave when cornering, was a welcome surprise. I’ve rarely felt so planted on such a lightweight bike.

I’m of the opinion it might even be pretty aero. While Factor shares no data to prove my point, I certainly didn’t feel the bike was holding me back at high speed. Plus the VAM presents a clean, slim profile to the wind, engineers having cleverly integrated cables without increasing the frontal area of the head tube.

To do this a D-shaped steerer tube has been employed so the cables have space to run through the head tube without the need to upsize the upper headset bearing.

The knowledge

In short, the O2 VAM is a complete bike. Its combination of attributes marks it out as something special. What I like is that Rob Gitelis, industry veteran and Factor’s owner, is candid about the fact the bike required some pretty special engineering knowhow and fabrication methods to get to where it is. A superhero is only as good as its origin story and Factor doesn’t scrimp on the details.

Gitelis says this is the most expensive frameset he has ever made. When you consider he has owned factories that manufactured for Cervélo and Scott, and that Factor also boasts the extremely complex One in its range (featuring a split down tube and external fork steerer) you can start to appreciate the sentiment.

The main tubes use Nippon Graphite Pitch fibre, an incredibly stiff, incredibly costly and very difficult material to work with. Boron filaments have been added to the seat tube for both compliance and their ability to cope with the compressive forces of the rider’s weight.

Textreme, a premium spread-tow fibre often used as a top layer for visual effect, has been used as the base structure at tube junctions, chosen for its proficiency at being moulded into complex shapes.

All these unusual materials are subjected to equally unusual manufacturing methods. Latex-covered Styrofoam mandrels are used in the moulds, so it’s possible to compress the composite at a higher pressure and thus expunge more resin. Every gram counts.

Gitelis says the bike was only financially viable because he owns his own factory so can absorb costs from individual projects into the expenses of the business as a whole.

Knowing it took decades of experience, cutting-edge fabrication techniques and a flagrant disregard for production cost adds to the O2 VAM’s appeal for me. Such forthright concessions are in contrast to the ambiguous marketing information we’re fed from many other brands. They rationalise the end product and its performance really nicely.

The core tenet of the bike is that it pushes things to extremes in some areas – the top tube is so fragile under compression that the bike ships with a ‘do not sit’ sticker along the middle – to create balance in others.

By doing so Factor has been able to create something that stands out in a highly congested category, and the result on the road speaks for itself. 

Learn more about the O2 Vam from Factor here.

Canyon Ultimate CF Evo Disc

As chosen by editor-at-large Stu Bowers

Read Stu's full review of the Canyon Ultimate CF Evo Disc here

I find myself in the peculiar position of championing two bikes in this month’s ‘clash of the light ones’. Having already made the case for the Specialized Tarmac I can’t ignore that there is another bike that deserves to be in the mix, one I’ve tested in its many guises over the years and which in this latest incarnation can boast a disc brake frame weight of just 641g. No wonder it gets the name ‘Ultimate’.

When it launched in 2019 the Ultimate CF Evo Disc (the first outing of what is now the Ultimate CFR) claimed to be a record-breaking bike, the world’s first sub-6kg disc brake bike. Not wishing to split hairs, the size medium I tested (issue 93) was a smidgen over at 6.16kg, but it was still unfathomably light for a disc bike, bearing in mind even now there are very few such bikes under 7kg.

I still recall the look of sheer amazement on the face of anyone who picked it up, but there was another reason why the Ultimate immediately sprang to mind when we started discussing our favourite featherweight racers. It was a bike that was instrumental in helping me achieve something I never thought I would do: being the first home in a mountainous European sportive.

The Figure Of Hate in the Pyrenees is a sportive that boasts nearly 5,000m of ascent over a gruelling 195km-long figure of eight, yet there were times when it actually felt like I was cheating. I’ll never forget the feeling as I tackled the biggest climb of the day, the hors catégorie Col de Pailhères.

With every pedal stroke the Ultimate surged forward as if turbo-boosted, and I can honestly say I’ve never crested a 2,000m peak feeling as fresh as I did that day. I’d attribute 90% of that to the bike. So too managing to escape my rivals on that climb and never looking back.

Ups and downs

What goes up must, of course, come down so unless you’re only interested in summit finishes and getting a lift back down the mountain then a lightweight bike must do more than just defy gravity.

The Ultimate really surprised me in this regard, being equally impressive in poise and handling down the many sinuous mountain descents of the Pyrenees. Because it was so light it needed just the deftest of touches to move it around but not in a manner that made it feel flighty or unstable, as was proven by the fact I hit a personal record of 92kmh on one descent. So not only did I climb faster than ever, I descended faster too.

Furthermore there was not a jolt of harshness to the ride feel, a fact I put down in large part to the seatpost assembly.  It was Canyon that pioneered the idea of a silicone sleeve wrapped around a seatpost that’s clamped lower down inside the seat tube. The rationale is there is more seatpost length available to flex, with the silicone offering some damping and filling what would otherwise be a gap between frame and post.

In this top-spec build that seatpost is an 87g Schmolke TLO, and with lowered clamp and sleeve combined the Ultimate remains the most vertically compliant bike I’ve ever tested that doesn’t contain pivots or springs. The result is that the Ultimate is day-to-day practical, as happy back in the UK as it was in the Pyrenees.

I’ve often been asked, ‘Can a road bike ever be too light?’ The answer isn’t straightforward. I’ve tested some very light bikes whose low weight has come at the cost of many of the other desirable traits, specifically stiffness and stability.

Some light bikes are too flexy due to the use of less material, others are skittish due to their high stiffness-to-weight ratio. But that’s not the case with the Ultimate. It is without doubt the most capable climbing bike I’ve tested.

It has often been said that anyone can make a light bike, but the real challenge is to achieve weight goals without sacrificing ride quality and practicality. A six-kilo bike is all very well but do you really want to ride tubulars every day or worry about being close to the weight limit for that stem? Thus in the Ultimate I feel Canyon has created a bike that does everything a bike needs to do – excels at these things no less – yet somehow does it for a shade over 6kg. 

Learn more about the Ultimate from Canyon here.

Trek Émonda SLR

As chosen by deputy editor James Spender

For a full review of the Trek Emonda SLR9, click here.

Halfway up the climb a guy came past me, out of the saddle because… he had no saddle. Given that the seatpost was still dangerously protruding I can’t say this was done for weight-saving, but what I can say is we were still 40km from the end of the Taiwan KOM. I can also say that by the time I struggled over the line this guy was already at the top in the queue for the food.

For those unfamiliar, the Taiwan KOM Challenge is 105km and runs from sea level to 3,275m. It is also excruciatingly hard and it’s why, when I rode it in 2017 along with my seatless chum, I decided I needed every advantage I could get from my bike. Thus I plumped for what at the time was one of the lightest production bikes available, the second-generation Trek Émonda SLR 9, kerb weight 6.08kg for a size 56cm.

To hit these numbers – the frame was a staggering 640g, the lightest of its day – Trek had employed every trick in the book. The frame featured a strikingly sloped top tube in the ‘compact Giants of the 1990s’ vein, a design that uses less material than a traditional shape.

There was also an integrated seatmast, another feature to save grams as it does away with the overlapping material of a seatpost. In the Émonda’s case it enabled more compliance too, offsetting what might otherwise have been an uncomfortable ride given the very stiff carbon fibres employed and the all-carbon, zero padding Bontrager XXX saddle – one of the lightest saddles available at 68g but one that wasn’t quite to my backside’s tastes.

Were I to have taken up full-time relations with this bike the saddle would have had to go, but otherwise I was utterly hooked. Bikes had been getting heavier with the advent of ‘everything aero’ and disc brakes, but here was a purists’ race bike.

Light at all costs, and light because it had been designed holistically. Added to that saddle was a set of specifically designed Bontrager Speed Stop rim brakes, Bontrager Aeolus 3 D3 wheels, a Bontrager XXX cockpit and even Bontrager tyres – the 185g (25mm) R4 Hard-Case Lites. By using its component arm Bontrager in tandem, Trek had blazed trails with one of the first homogenously designed road bikes.

Learn more about the Emonda from Trek here.

Heavier but faster

At the Taiwan KOM I came in five hours and nine minutes after, and only 181 places down from, eventual winner Vincenzo Nibali (3 hours 19 minutes). I was two places behind Rob Gitelis riding one of his original Factor O2s and competing in the over-50s category. Perhaps his bike was even lighter, yet I look back on that experience and think I couldn’t have chosen a better ride partner.

I did ride that Factor latterly (though to note, the O2 VAM is the lightened variation) and while it is impressive, the Émonda trumped the O2 in handling and comfort. In fact it trumped everything for a long while. Weight aside is was a ‘complete’ bike, light but near impeccable in every other regard too.

In the three years since, the Émonda has undergone a further facelift followed by full-on replacement surgery. First it got disc brakes, then earlier this year it got an entire overhaul. Gone is the compact shape, with the bike now looking much more regular side-on, although closer inspection reveals aerodynamically sculpted tubes and hidden cabling. Still, the ethos remains the same, even if somewhat a product of its time.

The new Émonda frame is actually 38g heavier than the outgoing model but, says Trek, it generates 180g less drag. That’s an 18-watt power saving or the equivalent of arriving at the finish line in 59 minutes when the previous generation would take 60.

This is indicative of where lightweight bikes are headed – it’s not good enough to just be light – but it does seem strange that the 2017 SLR 9 weighed 6.08kg, whereas the new SLR 9 weighs 6.82kg. But that’s disc brakes, aero tube profiles and hidden cables for you, all wonderful things to make a bike go faster, but all elements that manufacturers are desperately trying to pare down.

If the bike is faster overall, one can’t complain. Now where do I sign up for the next Taiwan KOM?

And the winner is...

They’re all light, but which is our light fantastic?

It’s an exceedingly tough call but while we each had our personal favourite, when we totted up the second place votes (OK, totted is a bit grand, we only had three to count), there was a clear… draw. That wasn’t supposed to happen.

Stu’s favourite alternative was the Trek Émonda, while James chose the Canyon Ultimate. This left Sam to be incredibly unhelpful, having given a somewhat leftfield vote to the BMC Teammachine (although the BMC does deserve honourable mention). So it was back to socially distanced arguing up a windy hillside in the New Forest (at the time of arguing, a Tier 1 area).

Unequivocal was the fact that the Ultimate was the significantly lighter bike, yet all agreed the Émonda is truly excellent, a worthy steed and unlike the others, boasting some seriously flamboyant paintwork.

Brands often sneak gram-savings in via lack of paint, which can weigh well over 100g a frame, so it’s little surprise the other three bikes here are basically variations on black. But while the Émonda would win a catwalk we’re not that superficial. No, the defining factor came down to day-to-day usability.

The Tarmac SL7 could well be said to be a superb all-rounder but it doesn’t excel – or perhaps excite – in any one area. The Émonda by contrast does, being wonderfully stiff and punchy up climbs and out of the traps. So too the Ultimate. But when the road gets rougher the Émonda gets a touch jarring while the Ultimate continues to roll with pronounced comfort, and all told the Ultimate just handles that much more sweetly. Which is a rare thing in a truly lightweight bike, and it’s why the Canyon Ultimate CFR is our overall winner.

It will get you to the top first by a nose, but will have you at the bottom by several bike lengths and a broad smile.