“You’re missing half your fork!”
Ride a mountain bike with Lefty and you’re bound to hear some variation of that well-worn joke. Though Cannondale’s iconic Lefty fork has been around for over 20 years, some riders still like to mock its appearance and question why it even exists. They probably just don’t know enough about it!
Are Lefty forks weird? Yes. Are they good? Definitely. Cannondale has a long reputation as one of the most innovative brands in cycling and it has never been afraid to break the “rules” of traditional bike design in search of performance.
After spending a few months on Cannondale’s latest Lefty Ocho, I’ve become a bit of a fan. Love it or hate it, the Lefty is unquestionably unique and clever, and it boasts a cult of loyal followers. Read on to learn more about the history of the Lefty, its special technology, pros and cons, my personal experience on the new Lefty Ocho, and why you should consider riding a Lefty.
The Lefty story begins with a suspension product that plenty of vintage mountain bike nerds will be familiar with: the HeadShok.
In the early ‘90s, mountain bike suspension was emerging. The first forks tended to lack stiffness, which compromised control when riding off-road. Cannondale sought to fix that problem with the HeadShock. Introduced in 1992, this new design moved the spring and damper away from the fork legs to inside the head tube and provided 50mm of travel.
Even back in the ‘90s, Cannondale employed a key design feature that would find its way into the Lefty: needle bearings. Instead of bushings used in other forks, the HeadShok moved on four strips of needle bearings sandwiched between the inner and outer tubes, keeping stiction to a minimum.
As riders demanded more travel than the HeadShok could offer, Cannondale moved the technology outside of the head tube and created the downhill-oriented Moto fork in 1996. The Moto was essentially a dual-crown fork made up of two HeadShoks mounted on each side. The fork went through several iterations that usually provided 100-120mm of travel. The most famous version was the Moto DH fork found on the legendary Fulcrum downhill bike.
Soon, Cannondale engineers began experimenting to create a lighter version of the Moto fork for XC and trail riding. They realized the simplest solution was to rely on the Moto's extremely stiff design and essentially chop the fork in half. The Lefty was born, officially launching in 1999.
The Lefty has taken many forms over the last 20 years but was primarily an XC fork with 100-120mm of travel. Recently, the Lefty Supermax provided longer-travel versions for trail and enduro bikes with 130mm-160mm of travel, and the Lefty Olaf was made specifically for fat bikes. In 2015, the Lefty Oliver was introduced as the first production suspension forks for gravel riding. It was found on the Slate gravel bike and provided 30mm of travel.
Cannondale’s latest Lefty offering, the Lefty Ocho, is a cross-country fork with 100-120mm of travel. It is a huge leap forward for the Lefty, packing all of that technology into a single-crown design. Unlike its dual-crown predecessors, the Ocho also uses a conventional tapered steerer, essentially compatible with any modern frame. It’s currently found on the F-Si hardtail and Scalpel full-suspension XC bikes. It is also the basis for the second-generation Lefty Oliver on the Topstone Lefty gravel bike.
Brazilian champion, Henrique Avancini on the Lefty Ocho | Photo: Bartek Wolinski/Red Bull Content Pool
Over the years, the Lefty has had great racing successes. Italian Marco Fontana won a bronze medal at the 2012 London Olympics (where he finished without a saddle!). Henrique Avancini won XCO and XCC races in the 2020 UCI Mountain Bike World Cup, and multiple riders have won Unbound Gravel titles aboard Cannondale Slates equipped with the Lefty Oliver.
The Lefty fork consolidates all the components of a conventional fork into a package that’s essentially half the size. To accomplish this, Cannondale used clever engineering to help the Lefty match and even exceed the performance of conventional XC forks.
Note the flat sides in the upper part of this Lefty Ocho stanchion | Photo: Cannondale.
If you’ve ever played with a rear shock that’s been removed from a bike, you’ll notice that it’s easy to rotate the shaft within the body of the shock. This is because the shock is essentially a cylinder within a cylinder. This is also true of a conventional fork leg. Obviously, rotation is undesirable because the front wheel has to stay aligned with your handlebars to maintain control. To prevent twisting, forks need to be “keyed.” For conventional forks, this is handled by the fork arch and axle that tie the lowers together and prevent them from rotating independently.
Because the Lefty is single-sided, there’s no fork arch or axle with two fixed sides. Instead, it uses a design feature that originated from the first HeadShok. The stanchion itself acts as a key. The upper portion of the stanchion has four flat sides that slide into a tube with matching flat sides to prevent the shaft from twisting. Rather than a conventional cylinder-in-cylinder design, the Lefty is square-in-square. The one exception is the new Lefty Ocho which is three-sided, but more on that later.
A keyed stanchion has a couple of benefits. First, the shape of the tube provides greater fore-aft and torsional stiffness than the round tubes used on conventional forks of the same travel and weight. This stiffness reduces front-wheel deflection and improves steering precision and control in rough terrain. Second, the flat sides allow a Lefty fork to use needle bearings instead of bushings.
Strips of needle bearings used on the flat sides. In the new Lefty Ocho, the three-sided bearing strip is called the "Delta Cage." | Photo: Cannondale.
Needle bearings are a type of roller bearing with long, thin cylindrical rollers resembling needles. Compared to ball bearings and ordinary roller bearings, needle bearings have more surface area in contact with the races, so they can support high loads like those experienced by a suspension fork. A Lefty moves on thin strips of needle bearings that are placed on each flat side of the inner tube.
Conventional forks with round tubes can’t use needle bearings because telescoping assemblies require a flat surface for the bearings to roll across. Instead, conventional forks move on bushings, which are essentially plastic rings. Bushings have more “stiction,” or static friction that needs to be overcome before the fork moves into its travel. When compared to bushings, needle bearings feel nearly frictionless and allow the Lefty to quickly and easily move into its travel.
Bushings also tend to bind when the tubes flex from torsional forces. Needle bearings, however, aren’t affected by this. In a Lefty, the vertical movement of the fork is separated from other forces because the bearings can still spin and move as the fork flexes, allowing it to continue responding to the terrain.
A Red Bull MotoGP Rookies Cup KTM with an inverted or USD fork. Note the stanchions are at the bottom. | Photo: Gold & Goose/Red Bull Content Pool.
For years, high-performance motorcycles have used inverted or upside-down (USD) forks, a design where the stanchions are at the bottom. Because upside-down forks are thicker and stiffer at the head tube where leverage is greatest, they perform better under hard braking and cornering.
Many manufacturers have attempted to bring upside-down forks to mountain biking but most products have been short-lived. The discontinued RockShox RS-1 is a good example, and before that, Manitou’s Dorado, Maverick’s Duc, and Marzocchi’s Shiver, to name only a few. Manufacturers were never able to strike a balance between stiffness with weight. Plus, upside-down forks often required proprietary hubs. Due to its low weight and Cannondale’s continued commitment to the design, the Lefty has been the most successful upside-down mountain bike fork to date.
The Lefty Ocho
The Lefty Ocho was released in 2018 and is the eighth (hence the name) iteration of the Lefty fork. It has a few key design improvements that have made it the best-performing Lefty yet.
The biggest difference between the Ocho and its predecessors is the single-crown design. Since the beginning, Lefty forks have used a dual-crown design, similar to those found on downhill forks. Having a crown that supports the fork both above and below the head tube added stiffness but posed some compatibility issues with frames and stems.
With the Ocho, Cannondale made a fork that is both more elegant and compatible with most frames. The upper assembly has been made thicker than a conventional fork crown to achieve rigidity comparable to the previous dual-crown designs. This allowed Cannondale to use a conventional tapered steerer that will fit most frames and stems.
The four-sided stanchion that was used in all Lefty forks for nearly 20 years was changed to a three-sided design in the Ocho. The reasoning is simple, three strips of roller bearings weigh less than four. Cannondale also claims that there is less friction in the system with fewer contact surfaces.
Because the overall length on the Lefty Ocho is shorter, the air piston and damper were redesigned with a lower stack height to fit into the new chassis. In previous Lefty forks, it was technically possible to add volume spacers, but it generally required aftermarket spacers or a homemade bodge. The Ocho now has proper OEM volume spacers, called Ramp Clamps, for those looking to tune the air spring. Adding a Ramp Clamp increases the force needed to bottom out the fork by about 10 percent.
The Ocho also uses a new StopLock brake mount that lets you remove the entire caliper (necessary to remove the front wheel) by turning a single 5mm hex bolt 180-degrees. It’s quicker and easier to use than the old sliding mounting system, and it provides perfect alignment every time you reinstall the mount.
2021 Cannondale Scalpel Hi-Mod.
The Ocho comes on the 2018+ F-Si hardtail and Scapel full-suspension XC bikes. It is also available aftermarket. There is an alloy version ($1,000, 1,735 grams) that uses a forged aluminum upper, and a top-of-the-line carbon version ($1,500, 1,446 grams) that costs more but weighs nearly 300 grams less. It comes in 55mm offset for 29” models and 50mm for 27.5” models, which Cannondale says suits the slacker head angles of modern XC bikes.
For 2021, Cannondale announced the Lefty Ocho Carbon 120mm (1,550 grams), a longer travel version of the original Ocho with a thicker, stiffer stanchion. It’s designed to compete with light 120mm trail forks like the Fox 34 Step-Cast and RockShox SID.
The Lefty Oliver
Cannondale Slate with the Lefty Oliver.
Gravel cycling is a relatively new genre and gravel bikes are still evolving. When Cannondale’s revolutionary Slate gravel bike was released in 2015, suspension forks weren’t available for drop bar gravel bikes. Cannondale saw an opportunity to use the stiff and lightweight Lefty design in this new application.
The Slate came with a gravel-specific version of the Lefty called the Lefty Oliver. It had the same lightweight chassis as the Lefty PBR carbon with the travel reduced to a modest 30mm. The fork was efficient but took the edge off rough and bumpy gravel roads. The Lefty Oliver has achieved success with multiple wins at Unbound Gravel, the world’s premier gravel race. Other brands have since followed suit and brought gravel-specific suspension forks to market, such as the Lauf Grit, Fox AX, and MRP Baxter forks.
After the Slate was discontinued in 2019, the Topstone Carbon replaced it as Cannondale’s flagship gravel bike. In 2020, Cannondale unveiled the Topstone Lefty, the Slate’s spiritual successor. The Lefty Oliver gravel fork returned, this time based on the sleeker single-crown Lefty Ocho.
The two greatest performance benefits of the Lefty design are greater rigidity and reduced stiction. As explained above, the tube shapes and upside-down design contribute to the greater overall stiffness. Needle bearings reduce stiction compared to bushings and eliminate bushing bind when bending and twisting forces are applied to the fork.
Compared to a conventional fork of the same travel, the stiffer Lefty should provide more precision, control, and active suppleness in rough terrain, or under hard braking and cornering.
These performance benefits can be seen in this demonstration by Beukers Bike Centre below:
The impressive rigidity of the Lefty chassis is clear when the presenter is able to lean his full weight on the fork without substantial flex. With a wheel mounted, the demonstration shows that torsional forces applied to the wheel (like you’d experience riding through a rock garden or a fast corner) have a great effect on the conventional fork’s ability to move, while the Lefty still compresses freely.
Of course, this demo was put on at a Cannondale dealer by a Cannondale representative so it should be taken with a grain of salt. The conditions of the demonstration may be favorable to the Lefty. It’s also over 10 years old and it features forks that are no longer in production. But the key differences shown in this video are still applicable to forks produced today.
Another video I’d encourage the Lefty-curious to examine is Pinkbike’s “28 Bikes Bottomed Out In Ultra Slo Mo (1000 FPS)” video. Viewed in slow motion, the Lefty Ocho visibly flexes less than its competitors, the Fox 32 Step-Cast and the RockShox SID. It even appears stiffer than several heavier trail forks like the Fox 34 and RockShox Pike. Though not exactly scientific, this supports the Lefty’s claim to superior rigidity.
The Lefty is more than light enough for World Cup XC racers. The stiffness helps Henrique Avancini navigate this gnarly rock garden. | Photo: Bartek Wolinski/Red Bull Content Pool.
Notably, this increased rigidity comes without a significant increase in weight. Through the years, the Lefty has remained competitive with the lightest XC forks. The current Lefty Ocho carbon has a claimed weight of 1,446 grams which makes it comparable to the Fox 32 Step-Cast (1,443 grams) and the SID SL Ultimate (1,326 grams) while having stiffness comparable to heavier, more trail-oriented forks like the Fox 34 Step-Cast (1,623 grams) and the 35mm stanchion RockShox SID Ultimate (1,610 grams).
One last thing to note is that it’s possible to remove the tire without removing the front wheel because there’s no right fork leg in the way. This can make changing tires or performing trail-side puncture repair slightly easier. It’s not a big deal, but a fun party trick nonetheless.
So what compromises do riders face when owning and riding a Lefty?
The biggest issue for the average rider is the Lefty’s proprietary technology. Conventional forks can take advantage of widely available components like wheels, headsets, and stems, and easier serviceability.
Because the Lefty is single-sided, it can’t use a conventional fork axle. It requires a proprietary Lefty hub that mates with the tapered axle. (The axle is actually another contributor to the Lefty’s stiffness. It is forged as a single piece with the stanchion, and the tapered shape creates a strong and rigid structure.) Because it requires a special hub, replacing or upgrading wheels can be an added expense. Riders looking to change their front wheel have limited off-the-shelf options and may need to rely on custom wheelbuilders.
Removing the front wheel also requires removing the brake caliper because the wheel is removed horizontally rather than vertically. This is a non-issue with the Lefty Ocho’s StopLock brake mount, but on older models, it can be a slightly annoying procedure requiring riders to undo brake mount bolts to remove the caliper.
The previous generation dual-crown Lefty forks also used a straight 1.5” steerer that required Lefty-specific headsets and stems. That is no longer the case with the new Lefty Ocho, which uses a conventional tapered steerer, but riders interested in Cannondale bikes with the older Lefty forks should be aware that they require stems compatible with 1.5” steerers, if they plan on customizing their cockpit.
Serviceability is the biggest concern a potential Lefty owner might have. Most conventional forks are easily serviced at most bike shops. However, due to proprietary technology, parts, and tools, Lefty forks need to be serviced by Cannondale dealers or authorized HeadShok service centers. With older Lefty models, if parts fail and need to be replaced, riders could potentially face reduced availability and higher prices. Buyers looking at older discontinued versions of the Lefty (essentially everything besides the Lefty Ocho and new Lefty Oliver) should carefully consider serviceability and parts availability.
As models like the Lefty Ultra, Supermax, and Hybrid age, parts and people who know how to fix them will be harder to find.
Intrepid home mechanics can potentially do the work themselves since service kits and instructions can be found online. Or, if you don’t live near a Cannondale dealer, you could also ship your Lefty to an approved service center. There are good options in the U.S. that specialize in Lefty forks.
Lefty service intervals aren’t too different from those suggested for Fox and RockShox forks. Major services for the air spring are recommended every 100 hours/annually, and every 200 hours/biannually for the damper.
The one notable difference is the suggested 50 hour “bearing reset.” All Lefty forks need periodic resetting of the needle bearings. Over time, the needle bearing strips can migrate from their original position, reducing the available travel. A bearing reset is actually required service for all linear/needle bearing devices. Resetting the bearings is a quick and easy process. Simply remove the air and firmly bottom the fork out a few times and the bearings will be repositioned. It takes about the same amount of time as putting air in your tires or lubing your chain.
There is one final thing to note: For many Lefty skeptics, the greatest downside is its appearance. Humans are a species drawn to symmetry, and some have become so accustomed to the appearance of conventional forks, that the single-sided Lefty can seem unnatural. Of course, beauty is in the eye of the beholder, and I for one think the Lefty forks look incredibly cool. And no, Lefty forks don't pull to one side.
I have always been a bit Lefty-curious, eyeing the many Lefty-equipped bikes that come and go through The Pro’s Closet. I had tested an older Scalpel, but didn’t actually ride a Lefty long-term until the Cannondale Slate. It wasn’t a mountain bike, but the precision and feel of the Lefty Oliver gave me a taste of what to expect from its longer-travel cousins.
I finally got a Lefty mountain bike when I picked up a special-edition F-Si hardtail. I wanted to know how the Lefty would perform on technical trails so I tested the bike at Hall Ranch, a local spot known for fast and loose descents and a technical, extended rock garden with rugged features that can overwhelm most lightweight XC bikes.
Though not excessively heavy, I am no featherweight XC rider. I weigh 185 pounds and I can easily exceed 200 pounds with riding gear. Because of my weight, I can feel most XC forks flex when charging into rough terrain. The flex I felt riding the Fox 32 Step-Cast was a major reason why I’ve ridden a Fox 34 Step-Cast on my last two XC bikes. The stiffer fork makes me feel more confident on tough descents. That isn’t a knock against the 32 Step-Cast. XC forks serve a specific purpose and low weight is their biggest priority. Experienced XC racers know how to ride these forks and respect their limitations.
The carbon Lefty Ocho, however, feels nothing like the Fox 32s and RockShox SIDs I’ve ridden in the past. It’s so torsionally rigid that it feels closer to the trail-oriented Fox 34 Step-Cast. It’s perhaps even a touch stiffer. I was impressed with how immediately confident I felt smashing the front end of the F-Si into rocks and landing deep off jumps and drops. The suggested air pressure was pretty close to bang on, and I haven't feel the need to add any volume spacers.
I can’t say I’ve ever noticed a conventional fork bind when loading it up through rough terrain, g-outs, or fast corners. But I can say that the Lefty Ocho always feels extremely supple, especially for a fork with a mere 100mm of travel. Thanks to the needle bearings and the fork’s ability to remain active under torsional forces, the traction and sensitivity are both exceptional.
I'm pushing the bike harder than expected with the Lefty Ocho. I put trail tires on to complement its excellent downhill performance.
My personal opinion right now is that the Lefty Ocho is the best performing XC fork on the market. Though its main competitors, the Fox 32 Step-Cast and RockShox SID SL, edge out the Lefty Ocho in the weight department, I don’t think they come close to the Lefty’s stiffness or initial sensitivity. To me, it’s most noticeable when hitting a square edge at speed, plowing into chattery roots and rocks, or landing nose-heavy off a drop. The Lefty is simply more adept when the riding gets rough and wild.
I have yet to service the fork, but I live near a Cannondale dealer so I don’t foresee any issues. The only item on my wish list for the Lefty Ocho is the option for a lock-out control on the crown. Currently, it’s only available with a remote lockout. I’d welcome an option similar to the previous generation Lefty PBR which used a push-button lockout on top of the fork to cut down on handlebar clutter. The new Lefty Ocho 120mm (1,550 grams) discards the remote, and could be the answer if I ever want to upgrade to an even stiffer fork with a bit more travel.
Riding is believing, so it’s at least worth seeing how the Lefty feels on the trail. However, the current generation Lefty Ocho only provides 100-120mm of travel and is aimed at XC and trail riding, so it won’t work for every type of mountain biker. Though it’d likely be welcome, there are no plans to create a long-travel version of the Lefty Ocho. Cannondale seems happy to keep the Lefty in the short-travel realm, turning to Fox and RockShox forks for its longer-travel trail and enduro bikes.
The Lefty Ocho is ideal for hard-charging XC riders who value stiffness and handling more than having the lowest weight possible (though keep in mind that at 21.5 pounds, my F-Si is still very light). When it comes to maximizing downhill and cornering performance in a lightweight package, the Lefty Ocho is hard to beat. It works so well on the F-Si that I expect it can only get better when paired with the full-suspension Scalpel or the Topstone gravel bike (reviews to come).
The Lefty Ocho also suits me because I actually enjoy all the curious looks it gets out on the trail. Nerds like me love weird bike tech and the odd “you’re missing half your fork” quip has actually led to some fun, in-depth conversations. Most people just want to know how the fork rides. Overall, it’s left a strong impression on me and I speak very highly of it. I wasn’t ever a Lefty skeptic, but after spending time on a Lefty, I’m definitely becoming a believer.
Are you a Lefty skeptic or believer? Do you ride a Lefty fork? Do you want to? Let us know in the comments!