Bikes of the Bunch: Unno Aora, the world’s lightest mountain bike frame

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Anyone reading this will have been bitten by the cycling bug, a bite that causes a deep obsession with no cure. But what happens when that bug consumes your life?

Adam Kerin of Zero Friction Cycling knows this all too well. In the past few years, the former police officer has spent his work days, evenings and weekends focussed on a small online business that specialises in drivetrain efficiency and durability. He’s quickly gathering a wealth of knowledge in the space, and you’ll likely recognise his name from our previous best chain lube feature.

Kerin has long been into cycling, but a few years ago he was bit once again. This time by mountain biking, and it didn’t take long before he was obsessed with marginal gains within a whole new segment.

‘Superbike’ is a term thrown around a little too much in the road bike world, but rarely is it said about a hardtail mountain bike. But that’s exactly what Kerin set out to build himself to better his cross country race results.

With some advanced knowledge in speed optimisation, an impressive amount of research, four months of waiting on boutique parts, and a (very) generous budget, the result is an 8.5kg bike built to remain reliable for cross country and marathon mountain bike racing. Here we dive deep into what Kerin considers the best-performing hardtail money can buy.

A 730g mountain bike frame from Spain

Kerin only found mountain biking at the age of 42, and as the Adelaide local will attest, he never believed it would lead him to chasing A-grade podiums. His 2016 Trek Top Fuel 9.9 is by no means a slouch on the race track, but having the bittersweet taste of second place on his tongue, he thought it was time to get a bike that played into his climbing strengths. The search for the ultimate hardtail began.

It was good friend of Kerin’s that put him onto Unno, a small mountain bike frame company based in Barcelona, Spain. The company specialise in in-house-made carbon fibre frames that typically push the boundaries – whether it be geometry, painstaking design, weight or simply, price. In the case of the Aora, it’s the world’s lightest hardtail frame, tipping the scales at just 790g including the derailleur hanger, rear axle and seat clamp.

The key face behind the brand, Cesar Rojo, is best known for his pioneering approach to geometry. He was responsible for the early envelope-pushing designs from Mondraker bikes, and has certainly helped shape the current movement for cross country bikes to offer more trail-friendly geometry.

And while the weight and approach to geometry had Kerin drooling, the selling point was arguably the exclusivity of owning a bike that is limited to a 50-unit annual production and is produced in a single size. Yep, just one size, and at 177cm, Kerin fit it well.

Unno Aora bikes of the bunch - dream race hardtail
It wasn’t long before Kerin would receive a large white box covered in a silhouette of the carbon pieces used to make it. Not only was it the first of its kind in Australia, but it was also the first to leave Spain.

“The frame was all I had dreamed of and more,” says Kerin. “It looked beautiful, the finishes at bottom bracket, headset and other mounting points were flawless. And the claimed weight of 730g for a bare frame was bang on. What’s more, despite that astoundingly low weight, they didn’t skimp on anything.

“[The frame features] full carbon tube guides for the rear brake line and rear mech – so it was literally just pushing the line in and it popped out the other end for rear brake. Full internal routing guides are rare, and definitely unexpected on a frame this light!”

With such an impressively light frame in hand, Kerin explains that he had to restrain himself from simply chasing grams. “It would have been easy to go for a sub-8kg build, maybe even nudging 7.5kg, however, this will be my number one race bike, and so some selections were based on what I believed would deliver me the absolute best performance, and sometimes a bit of extra weight is well worth having.”

Shimano versus SRAM, a battle of 12-speed groups

Kerin’s internal battle was between SRAM’s Eagle AXS 12-speed wireless and Shimano’s XTR M9100 12-speed mechanical.

Unno Aora bikes of the bunch - dream race hardtail
SRAM’s new Eagle AXS wireless is a very desirable groupset, but it wasn’t a clear decision for Kerin.

“The reality is for the last five years SRAM has grabbed hold of Shimano’s underwear and given them an atomic wedgie when it comes to the MTB market,” Kerin says. “SRAM 1×11 and then Eagle 12-speed groupsets have absolutely dominated and for very good reason.”

Despite that, Kerin still wanted to stick with Shimano’s new XTR. It’s lighter and from the brand Kerin has had the best experience with across multiple disciplines.

“You would think Shimano would want as few barriers to customers wanting to try Shimano over SRAM Eagle,” he says. “Instead, they throw an enormous barrier in the way of not open licensing the Micro Spline hub.

“When I was making purchases, I had a choice of three hubs – Shimano Scylence [which was subsequently cancelled], DT Swiss, or White Industries. Nothing against DT Swiss or White Industries, but all the wheels I was considering from very lightweight Extralite or AX Lightness, to the Crankbrothers Synthesis I settled on, I literally could not purchase with a Micro Spline freehub [Industry Nine has since been granted a license to offer Micro Spline hubs].”

In the end, Kerin sees it as Shimano forcing his hand to try out SRAM’s new AXS wireless. He now loves the clean one-less-cable look it provides.

“Once I saw them I couldn’t unsee them — they just had to be part of this build,” says Kerin of his decision to equip the Unno with CaneCreek’s eeWings titanium cranks. “[There’s] no strong argument to spend over double on these supposedly damn near indestructible cranks versus other, lighter, offerings like SRAM’s XX1 AXS or RaceFace Next SL.”

Unno Aora bikes of the bunch - dream race hardtail
Bling, everywhere.

Those cranks are fitted with a deliberately matched titanium oval ring from Absolute Black. “The last time I checked, the major studies were a little inconclusive in determining benefit for oval rings for endurance efforts,” explains Kerin. “However, the top studies do show a strong likelihood there is a benefit for short high power efforts. Of course that applies to XC events, and even in MTB endurance events one is repeatedly faced with short steep ramps that require 400 to 600w for around 30 to 60 secs just to get up them.

“As soon as I switched it was easier on such climbs to get past the dead-spot in the pedal stroke, and I’ve been a convert for MTB and CX since – although I haven’t gotten around to putting them on my road bikes yet.”

The choices of a drivetrain efficiency expert

As someone who spends his days obsessing over what makes one chain lube better than another, or how certain coatings impact chain wear, Kerin’s personal choices in drivetrain upgrades are worth your attention.

The biggest gains available are with the chain. No matter the chain used, Kerin coats it with Molten Speed Wax – a product that’s applied through submersing the chain in a hot bath of the modified paraffin wax mixture. “I only need to boil the kettle to clean the chain after a dusty or muddy race,” says Kerin.

As a teaser for an article in the works, Kerin chooses to use a different chain depending on whether he’s training or racing. “[The] SRAM Eagle XX1 / AXS chains are the longest-lasting in the world, but they have been tested by two separate independent labs as being very slow.” For racing, Kerin chooses KMC’s Eagle x12 chain, “[which has been] tested as pretty much fastest chain to date, but is also extremely short-lived, with controlled machine testing being not too great, and field testing taking an average of 600km of mountain biking for it to reach .5% wear mark.”

According to Kerin, it’s a case of 4W versus 8W at 250W load. Stay tuned on this topic — an in-depth feature exclusive to CyclingTips is in the works.

Unno Aora bikes of the bunch - dream race hardtail
There’s a number of small pieces hidden away, each designed to bring another level of performance to what the mainstream brands offer.

Looking to the rear derailleur and Kerin has splurged for an ultra-premium CeramicSpeed 3D-printed titanium jockey wheel in a larger 14T, but interestingly, only for the lower tension wheel, while the top pulley is kept stock.

“When it comes to any little frictional savings with jockey wheel upgrades, the lion’s share comes from the tension wheel,” Kerin says. “Should the lovely CeramicSpeed bearing get a tough time with contamination, I then have a spare wheel [CeramicSpeed sells the wheels in pairs] to pop on whilst I sort it out with an ultrasonic clean.” As an added bonus, it matches those titanium cranks.

Speaking of those pulley wheels, Kerin says “It is a Rolls Royce build and CeramicSpeed [is] still the Formula One of bearings. Personally, I can pop bearings out for ultrasonic cleaning willy nilly, and it’s an easy choice on this spare-nothing dream build.”

However, he actively recommends differently for most customers. “I do offer CeramicSpeed upgrades, but HSC and Kogel are still fast and at a more sane price point,” he says. “It is often well worth it for a customer to upgrade from a cheap, draggy bottom bracket to a HSC or Kogel and save 1W or more, but it is hard to recommend spending double or even triple that to save a further 0.1W with a CeramicSpeed.”


Equally boutique component selections

It’s clear there’s still room for road disc brakes to come down in weight when you see a product like Trickstuff’s 316g Piccola brakeset. Yep, 316g for the pair, including levers, hoses, brake pads and fluid – just add rotors. And they offer an adapter that allows the SRAM AXS shifter to mount directly to the lever, saving more grams again.

Unno Aora bikes of the bunch - dream race hardtail
The lightest disc brakes on the market apparently work extremely well, too.

“It’s a very clever design where the master cylinder is braced by handlebar rather than needing its own reinforced body,” Kerin says. “Plus, they look amazing and work incredibly well, too. They are, however, just as expensive as they are irresistible.”

Those brakes are set up with Quaxar IRIS rotors: “they’re lightweight, look awesome, and have the best braking power and modulation of any 160mm disc I have tried yet,” Kerin says. “It will take something special to make me want to try something over these now.”

And what about wheels?

“While there were certainly lighter options, the Crankbrothers Synthesis are arguably the highest performing XC wheelset,” Kerin says. “The same friend who put me onto the Unno also put me onto these wheels, and everything about them simply clicked with me. I really liked how they went about their testing of theories between stiff vs compliance wheels.”

Unno Aora bikes of the bunch - dream race hardtail
The Crankbrothers Synthesis wheels feature different designs front to rear.

The creation of these wheels came about when Jason Schiers, co-founder of Enve Composites, and former Adelaide local Mello Bowmeister (of Bowmeister wheels), came together. In their extensive blind testing with a group of nearly 100 riders, they found people were evenly split on preferring stiff wheels (like Enve) versus more compliant wheels (like Bowmeister). That same sample group was given a stiff front wheel and compliant rear, and it was almost universally disliked. The opposite proved true when riders were given a compliant front wheel and a stiff rear – exactly what the Synthesis aims to do.

In addition to the special compliant and stiff combination, the front wheel offers a 26mm internal width, with a narrower 24.5mm at rear. They’re built upon the new Industry Nine Hydra hubs with an incredibly fast half-a-degree of engagement. “They’re not exactly heavy at 1540grams for the pair, however, that’s still about 400grams heavier than the lightest XC wheels,” Kerin says. “I believe that extra weight will pay me back when riding at my limit on the trails.”

Kerin took the same approach with his choice in tyres, saddle and pedals, too. Half a kilogram could have been saved in the tyres if this bike was about a number on the scale, but rather Kerin has equipped puncture-resistant tubeless tyres from Schwalbe. The choice in a SQ Labs saddle is based on perfect comfort during previous 12-hour endurance race attempts.

Unno Aora bikes of the bunch - dream race hardtail
HT pedals are not a common pick, but Kerin prefers them.

The HT pedals weigh somewhere between Shimano XTR and Crankbrothers Egg Beater pedals, but, says Kerin, “I can pretty much just throw my foot anywhere in the vicinity of the pedal and it clicks in.” That’s a slightly different experience to when I tested the same HT Leopard M1 Titanium pedals a couple of years ago.

Suspension fork choice was a battle between the Fox Step Cast 32 and the RockShox SID Ultimate Kerin eventually went with. “While the Fox is a little lighter and the performance is highly regarded, I went with the RockShox based purely on the service support offered in Australia,” he says. “I have a RockShox on my Trek and SRAM have also bent over backwards to ensure I’m not without it for long, while lots of people with Fox have warned me that service turnaround is far from quick.”

Unno Aora bikes of the bunch - dream race hardtail
These little pieces of plastic give you something to rest against without having to have your thumb under the grip.

Finally, you may notice some peculiar little nubs protruding from the inner side of the grips. These are TOGS, or Thumb Over Grip System. “I am one of those strange people who rides with their thumb over the bar,” says Kerin. “I always subconsciously move my thumb to the top. I ride with a soft grip and let things move around and self-correct.

“They’re one of my absolute favourite little items; I would now feel lost without them. Everyone should buy a pair as I need to ensure they stay in business forever, otherwise, I need to buy 10 pairs to last me for life.”

Named Artemis

“I’m one of those people that names all of my bikes,” Kerin says. “I’ve named the bike Artemis, the goddess of the hunt. I named it well before the Artemis project was announced to put a woman on the moon. I think NASA stole it from me.”

All told, this special Unno, Artemis, tips the scales at just 8.5kg with pedals and 100ml of tubeless tyre sealant sloshing around in each tyre. “I went as light as possible where feasible, but the performance was not compromised for weight,” he says. “Still, my rigid cyclocross bike is 8.6kg, and it’s similar in weight to many Cervelo S5 and Specialized Venge road bikes I see.

“I will be hunting A-grade podiums and the elusive 12-hour win at the Dirty Weekend where I have finished second the last two years in a row. I sure hope I’m faster on this given the investment,” laughed Kerin.

Build details

  • Frame: Unno Aora
  • Fork: RockShox SID Ultimate, 100mm with remote lockout
  • Headset: Chris King
  • Wheelset: Crankbrothers Synthesis XCT, Industry Nine Hydra hubs
  • Rear derailleur: SRAM Eagle AXS wireless, tension (lower) wheel changed to CeramicSpeed titanium narrow wide 14t.
  • Cassette: SRAM Eagle AXS, 10-50T
  • Chain: SRAM Eagle AXS for training, KMC x12 Eagle for racing
  • Crankset: Cane Creek eeWings titanium with Absolute Black titanium 34T oval chain ring
  • Shifter: SRAM Eagle AXS
  • Brakes: Trickstuff Piccola
  • Brake rotors: Quaxar IRIS Titanium-coated 160mm
  • Bottom bracket: CeramicSpeed PF4130 for BB92
  • Front tyre: Schwalbe Rocket Ron, 29×2.25in
  • Rear tyre: Schwalbe Racing Ray, 29×2.25in
  • Seatpost: MCFK
  • Saddle: SQ Labs 611 Ergowave Active Carbon
  • Handlebars: MCFK XC bars, 680mm wide
  • Stem: MCFK
  • Grips: ESI Chunky silicon
  • Pedals: HT M1 Titanium
  • Bottle cage: Tune Wassertrager 2.0 (just one at the moment)
  • Extras: TOGS (Thumb Over Grip System)


Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

Unno Aora bikes of the bunch - dream race hardtail

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