Sub 10 kilos (22lb) has always been a benchmark for the best lightweight mountain bikes. However, with XCO courses becoming more and more technical and riders demanding bigger mountain bike tires and the best dropper posts to tackle them, 10kg bikes are rarer than ever. Our top ten proves that there are still some sweet rides out there if you know where to look. Whether you want an ultimate-spec full suspension bike like Scott’s Spark RC 900 SL AXS, a road bike weight frame from Specialized or a super-unique frameset, there's something for everybody on this list.
In reality, you’d be hard-pressed to tell any difference in the ride of a 10.2kg bike and a 9.8kg bike but the psychological/bragging rights significance of going under 10kg is massive. Developments and demands of riders mean it’s harder than ever to hit that target though. 29-inch wheels, tires and forks will always be heavier than 27.5-inch or 26-inch (remember them?) but their smoother speed makes them an XC essential. Some top racers like Nino Schurter are routinely using 2.4in tires now too, while others are wide rim or wide handlebar fans.
Most of the world’s fastest racers are now using dropper posts for extra control on challenging courses despite a 400-500g penalty over fixed posts. Huge cassettes mean simpler 1x transmissions are often heavier than old double chainring setups too. Even remote control suspension adds significant weight, but again most racers won’t be without it for smashing smoother climbs.
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Best lightweight mountain bikes under 10kg
At 820g for a medium frame with rear axle and seat collar (averaging 760g/1.72lb without), Specialized’s new S-Works Epic HT frame is the lightest mass-production mountain bike chassis you can buy. Not only is it available in a full range of sizes - unlike the Unno - each size gets a slightly different ‘Rider First’ layup to deliver the right ride-feel. Unsurprisingly that’s the cliched ‘compliant over bumps but powerful through the pedals’ character touted by most manufacturers. The super-skinny, blade top seat stays combine with a deliberately damped 30.9mm seatpost to deliver a genuinely forgiving in-the-saddle ride. The sculpted front uses a Brain-equipped, 100mm travel, RockShox SID Ultimate fork. The fork crown uses a short offset for extra stability and the head angle is relaxed at 68.5-degrees. Add ‘short for XC’ 60-70mm stems and 760mm wide handlebars as standard and it’s a surprisingly composed charger on descents. The 30.9mm seatpost size gives you a full range of dropper options, too.
If you’re looking at a sub 9kg bike though you’re probably mostly about the acceleration kick and climbs, and Epic definitely delivers here. It’s not ‘Euro lab test’ rigid underfoot but there’s no trace of morale-sapping twist as the revs drop and the torque peaks. Specialized even fits a Quarq power meter to this flagship AXS spec as standard because it knows watts are as important to racers as weight. The automatic bump sensor built into the Brain fork lets you tune the rigid-to-flowing balance in a uniquely binary way and frees you up from fretting about remote levers, too. It’s got practical as well as podium-hunting detail with a threaded bottom bracket fit and clearance for up to 2.4in tires.
Decades of supporting many of the world’s top racers mean its own brand kit is seriously light, although its low spoke count (24 upfront) wheels can be a bit wayward when worked hard. If you can’t afford this flagship there are four different complete Epic HT bikes down to £2,250 and a frame-only option.
In terms of frame weight, Orbea’s carbon fiber Alma OMR race hardtail isn’t crazy light at over 1kg, but they’ve done something radical to get complete bike weight low enough to kill on the climbs. Depending on what fork you run, Orbea’s 550g Spirit Rigid fork will save you 800-1000g over a 100mm suspension unit to bring complete bike weight well under 9kg. The kinked, super-flat top tube is designed to help dissipate the extra shock coming through from the front end too, although the long, tapered, carbon legs deliver a smoother ride than you’d expect. The super-slim stays are designed for extra flex but there’s still plenty of meat around the cranks and chainstays for kicking hard and making that low weight count. The fork is also the same length as a 100mm travel unit so swapping around won’t disturb the agile, short wheelbase handling.
The same OMR frame appears on the top four Alma models with another four Alma models using the slightly heavier OMP frames. Whatever your starting point, Orbea’s ‘MyO’ customization program lets you pick and mix from a range of components to tune cost, weight and character. You can even choose from multiple color options (fully custom on the top models) so that you get a truly personalized Alma built for you in Orbea’s Basque factory. The direct sell model means they’re generally very good value too although you will have to wait longer for delivery than if you pick an off-the-shelf bike from your local shop.
Mondraker has redesigned the Podium hardtail for 2021, so it has a more conventional look but keeps its light weight and 'Forward Geometry.' The brand claims that it has created the world's lightest production frameset.
Born on DH race tracks thanks to the work of Unno’s Cesar Rojo and others, Forward Geometry was the spark point for the current trend for super-short stems on extended reach frames. Mondraker was the first mainstream brand to be ballsy enough to use the concept right across its range from gravity bikes to cross-country machines. The Podium was designed a while ago now but the 2021 model's geometry has been refreshed, bringing a 463mm reach, 68.5-degree headtube angle, and a 70mm stem on a size large.
If you can afford the price tag for this beast of a hardtail, then you'll be smashing the climbs in no time.
Santa Cruz’s original Highball race hardtail was so stiff it could make your feet numb in under an hour in the wrong shoes and rattle teeth out on rocky descents. That meant we weren’t expecting an easy ride when we met its new race rod. Santa Cruz has completely flipped priorities with the new Highball though, realizing that fighting fatigue and preserving performance is more important than ultimate power punch. While the 69.5-degree head angle is still pretty snappy the 450mm reach (large size) is long for an XC bike, which helps calm control on flat-out fast sections. The frame compliance also noticeably improves the bike’s ability to conform to the trail for traction as well as reducing the chance of you being rattled offline or ricocheting randomly off rocks and drops. The threaded bottom bracket and three bottle cage mounts are designed for the long haul. Despite removing over 200g from the old frame it gets a no weight limit, no questions asked, lifetime frame warranty.
Riders can also opt to equip their Highball with Santa Cruz’s Reserve carbon wheels. They’re covered by a similarly no-nonsense lifetime warranty and again the ride feel is obviously damped and shock smoothing rather than skittish and sketchy. That means you can hit stuff hard without worrying about comfort levels or construction quality and it’ll work great as a daily driver.
Unsurprisingly, power delivery definitely isn’t as taut as some pure racers, but trail connection and rollover performance are excellent.
A couple of years ago now, Trek created an all-new type of full-suspension bike, using what it calls ‘Isostrut,' a tiny but full feature remote control Fox air shock, hidden inside a Kashima gold stanchion that bolts into the cutaway top tube. The flat flex stays then stretch forward to a tube that slides along the stanchion, connected to the shock via top and bottom slots that also stop twist. Add a main pivot just above and in front of the chainring and you’ve got 60mm of travel with all the usual shock rate, pressure and damping adjustments plus a remote control lockout. Fewer pivots and linkages mean reduced mass and maintenance and it also gives a very clean frame look with room for two bottle cages if the race/ride is long or hot.
Trek has certainly committed hard to the concept too, with no carbon-framed, purely hardtail bikes in its XC lineup. ProCaliber 9.7 and below use its road-bike-derived ‘IsoFlex’ scissor frame. Meanwhile, the new Trek Top Fuel beefs up from its previous super-light and twangy incarnation, getting 115mm of travel out back with slacker angles, longer reach and a much stiffer power and precision-friendly ride.
While we personally have not tested the Isotrut-equipped Super Caliber yet, the top racers in the world seem to have no problem making it go fast on the trails. This is a very "XC" bike, so the unique design certainly won't be for everyone.
The current Spark RC900 SL rolls on 29er wheels and, despite the fact it’s a relatively old frame geometry, is still more progressive and tech trail-ready than most. It’s more than accurate enough to get really aggro with too, although singletrack speed fiends should check out the non-RC Spark models which get 120mm of travel and are still lighter than most race frames. Either way, the latest iteration also has the best Spark suspension by far, with proper chunder-calming, speed-breeding performance in its ‘Open' mode. Push the TwinLoc trigger on the bar though and you can toggle into a tauter, reduced travel ‘Traction’ mode for feisty climbs or fully lock it for sprinting, and that response is matched by the front fork, too.
A sub-1,800g chassis weight complete with shock and all the trimmings still makes the lightest, mass-production, full-suspension frame around. With multiple Olympic Gold, World Championship and World Cup wins under its belt there’s no disputing the Spark’s podium-dominating pedigree either.
This year's SL version truly is the ultimate Spark spec, complete with Syncros carbon spoked wheels, integrated Fraser cockpit, Fox SC33 forks and a full suite of SRAM’s game-changing AXS wireless groupset.
Cannondale is another brand that has always had racing close to its maxed-out heart and the F-SI Hi-Mod is loaded with typically left-field features.
Most obvious is the Ocho fork, the latest version of a left-leg-only suspension family that’s now 20 years old. The cantilevered single crown carbon fork (old Lefty forks were double crown) makes it the lightest Cannondale fork yet and it’s also competitively smooth once you find the set-up sweet spot. Even after a double decade on the faceted, inset needle-bearing leg technology, the tracking is still a head bender but you’ll soon learn to make the most of it on aggressive overtakes or tire ripping turns. The 55mm fork offset and short stems as standard make for very fast steering despite a balanced looking 69-degree head angle. The comparatively short reach (440mm on a large) and wheelbase make it an incredibly responsive ripper that needs a steady nerve if things get nasty rather than a naturally confident ride.
The Ballistec carbon frame shaves weight with a narrow shell 30mm press-fit bottom bracket and it was one of the first to adopt road bike style ‘Flat Mount’ disc brake fittings. It also uses a Cannondale-specific Ai wheel offset which you need to factor in when upgrading but, with ENVE carbon rims as standard on this World Cup replica, that’s unlikely to be an issue for power-and-precision fiends. It’s worth pointing out that this top-end Enve bar, post and rim-loaded build rides noticeably stiffer and more rattly over the rough stuff than lower-priced models with more compliant wheelsets. That makes the F-SI Carbon 2 our pick of the Cannondale pack at half the price of the Hi-Mod World Cup, although the gorgeous retro paint jobs of the limited edition ‘Throwback’ framesets will be hard to resist for those who remember the Tinker Juarez and Cadel Evans glory days of Cannondale.
Merida’s Ninety-Six is a totally proven machine, developed in conjunction with some of the most experienced top-level racers. It was also one of the first 29er full-suspension bikes to dip under the 10kg mark thanks to a 1,760g claimed frame weight. If you like your handling fast and your frames whippy it’s still right up there in the fast bike rankings, too.
As the name suggests the CF5 carbon fiber frame gives 96mm of rear-wheel travel via a short-stroke Fox shock with a remote lockout lever. You get a full pivot bearing set-up, not just flex stays, so even at 25 percent sag you actually get a very plush ride if you run the compression damper fully open. That’s great for rooty/rocky traction and making the rear travel seem longer than it is, but we can see most racers defaulting to the middle Trail setting for a tighter, more pedal-friendly feel.
An update to a 148mm Boost rear end has improved rear-end stiffness and the switch to a 44mm offset fork has also added some stability to the steering. That just means the 70-degree head angle is now just fast rather than outright frantic and the skinny frame means it’s still more articulated than accurate in overall feel. To be fair the super-light, minimal tread Continental Race King Race Sport tires aren’t even going to give enough traction to tax the steering much anyway.
The Reynolds TR429 wheels are a tight tracking set-up if you want to put something toothier on and the latest XTR on this 9.9000 version is similarly positive and punchy in feel compared to the previous vague version of Shimano’s flagship group. Unless you’re a diehard double chainring fan the unused front mech tab on the down tube does look a bit awkward though and definitely dates the frame.
Canyon has grown from a small trailer-based spares ‘shop’ at German XC races to a global bike-brand superpower with an ever-increasing number of World Cup and World Championship race wins under its belt.
This top-line hardtail features a 69-degree headtube angle, 1,154mm wheelbase, and 455mm reach on a size large. It also gets a sweet exclusive paint job, and the full build comes in at 8.9 kg.
For the build kit, the bike features a SRAM XX1 Eagle AXS drivetrain and a remote-controlled RockShox SID SL fork. SRAM also provides the braes with Level Ultimates bringing the stopping power. Reynolds Blacklabel XC wheels are paired with Maxxis tires to keep you rolling.
On a budget? There are multiple other Exceed models to choose from with more wallet-friendly build kits. They feature the same frame geometry but will have different components and will be heavier.
Even if you’re never going to be able to afford the €4,000 frame price or the single size doesn’t fit you, it’s still worth checking out the Unno website as an art gallery of aspiration bike building and design presentation. It’s taken ex-World Cup racer and Mondraker collaborator, Cesar Rojo, and his team over four years to create the svelte carbon sculpture of the Aora. The company only makes 50 frames a year in its surgically clean Barcelona design and manufacturing facility.
At 790g (fully equipped) it’s the lightest ‘production’ MTB frame available though and that’s not the only unique thing about it. A 67-degree head angle with minimal 85mm head tube height and super-short 418mm chainstays give it an ultra-responsive kick but confidently progressive handling. The naked finish and flowing lines also give it jaw-dropping looks before you even pick it up.
If you’re looking for the same handmade attention to detail and limited-edition exclusivity in a full suspension bike then Unno’s Horn has the same radical geometry but with 100mm of rear travel. At 1,600g without rear shock and rear axle, it’s not the lightest FS option, but you are getting true twin linkage swingarm mobility rather than just a flexy seat stay design. It's available now but you might need some time to save up.
Best lightweight mountain bikes: what you need to know
1. Full suspension or hardtail?
The other big weight penalty that racers are now routinely paying is opting for a full-suspension bike rather than one of the best hardtail mountain bikes. Unless it’s a super-smooth or strength-sapping high-altitude course most of the men’s World Cup XCO field will be on a double-damped rig, and more and more women are lining up on full sus every race. They’re a lot more fun and forgiving outside the tape if you’re not a completely competition-focused rider. That inevitably means a roughly 250g rear shock plus pivot bearings, other mounting hardware and extra frame parts piling on the weight. As a result, even the ultra-light 1,750g Scott Spark is still 900g heavier than the hardtail Scott Scale and most head-to-head, in-brand comparisons are significantly heavier. Softail bikes like Trek’s new Supercaliber or BMC’s TeamElite split the difference in weight and full suspension function to the point where neither brand now sells a conventional fixed frame pro-level bike.
2. Race Proven
Speaking of race replicas, you’ll often find that brands sell premium versions that are even lighter than the bikes their team riders use. That’s generally due to sponsor demands (RockShox SID forks are heavier than Fox SC32, Shimano XTR is heavier than SRAM XX1 etc.) but sometimes they just fit cost-no-object component mixes to create a super-light show stopper like Scott’s Spark RC 900 SL AXS.
3. Freaks and uniques
Some bikes like Orbea’s rigid forked Alma M-Ltd are lightened further than most of us would regard practical and Niner’s Air 9 RDO can be fitted with a chain tensioning eccentric bottom bracket so you can go single-speed and ditch gears altogether. Ultra-boutique brands like FRM produce complete ultra-light builds while Unno only hand-build its Aora hardtail in a single size. If you really want to see what’s possible then click on the infamous gram hating hangout weightweenies.starbike.com. Or check out how anti-gravity artists like Gustav Gullholm (Dangerholm on Instagram) get Scott Spark and Scale bikes down to 7kg with belt sanders, paint stripper and ultra-light carbon fiber cockpit and seating combinations.
NB: We’ve had to rely largely on manufacturers weights for this run down, so if you want to be sure of weights take your scales with you when you go shopping. Please contact us if any of the numbers are right off so we can update the feature for everyone else.