2013 Lefty Forks – Stiffer, Lighter, Stronger & More Durable
We’ve seen some race shots of Lefty prototypes earlier this year, but now all is revealed.
According to Lefty product manager Drew Hannah, this is the biggest innovation in Lefty since its inception 13 years ago. Cannondale has always claimed it to be lighter, stiffer and stronger than any other fork on the market thanks to its dual crown inverted design, which puts more material where it’s needed (40mm stanchion at the top, 32mm at the bottom) with two clamps at the top.
Keeping it smooth are four sets of needle bearings that roll between the upper and the lower stanchions. Compare this to the sliding on bushings of other forks, and Cannondale says it’s far smoother. In our experience, it is indeed pretty slick feeling. Because it’s squared off where it rolls on the needle bearings, it can’t twist, and flex is reduced.
There are no shortage of complaints of leaky forks, so with the new Lefty, the wanted to make it lighter, stiffer, stronger and improve durability…
For 2013, they have a new sealed Hybrid Bearing Design. There’s a new external sealing system that’s completely sealed against the elements. With their original design, the square section of the lower slider extended beyond the base of the upper stanchion. This made it impossible to seal well, which is why it had that ugly dust boot.
On the new ones, the tube is now round on the bottom, which allows them to use a much more effective wiper seal, similar to what you see on other forks. It also looks much better, and the new moto-inspired brush guard (optional, as shown here on their demo bike) has an integrated hose/cable guide for the front fork. All in all, it’s much cleaner looking, and it makes use easier because you can use a simple ring around the lowers to determine sag rather than having to measure it.
At the bottom of the upper, there’s a new Durathon Seal. Because the system seals so much better, they were able to put a 10cc oil bath inside the upper. Gravity keeps the oil right on the seal and splashing across the needle bearings. Within the seal is a Glide Bearing (beige) to assist with stiffness as the fork moves deep into its travel. Hannah says it actually gets stiffer the further you go into your travel because of the distance between the bushing and bearings increases (imagine grabbing your handlebar wider and you see why). The combination of the Glide Bearing (which, yes, is a bushing) and the Needle Bearings is what they’re calling Hybrid Bearing Design, and Hannah says the inclusion of the bushing doesn’t affect the smoothness.
Because the lowers are round, the square area is shorter inside the fork and they had to use shorter needle bearing stacks. Above, black is the original, the green is for 29ers and the white is for 26″ Lefty’s. Because these are shorter, the Glide Bearing is required to brace the lower. Even with it, though, Hannah says the Lefty has 1/4 of the friction because it’s using one bushing rather than four in a typical fork. On the trail, this translates to quicker breakaway from static position, which means faster, more supple action over small bumps.
With the Hybrid Bearing design, the new Lefty is laterally stiffer (side to side and front to back). Torsionally, it’s the same as the previous models, and Cannondale says its testing shows the Lefty to be substantially stiffer torsionally than standard forks at all points in its travel. This translates into accurate steering and precise tracking, which makes the rider more confident.
Back to durability. The needle bearings can migrate out of position under compression, which can cause noise and affect total travel. Now, there’s a reset spacer at the top of the upper that resets the needle bearing stacks at bottom out. In the photo above, you can see where the bearings bottom out against the silver spacer at the top. On previous models, you had to manually reset the needle bearings by pulling the fork apart. Now, you just ride. Hannah says if sag is set properly, you’ll probably bottom the fork often enough in normal riding to automatically reset them to the proper position. If not, you can just let all the air out, compress the fork completely, then air it back up and the reset is complete.
Above is merely a demonstration model, normally there’d be only white or only green bearing stacks. In addition to resetting the bearings, the silver spacer serves to terminate the travel when the bearing stacks hit them, creating the bottom out. Notice that the taller 29er needle stack effectively limits the travel because it hits the top spacer before the white 26″ stack would. That, in addition to the spacers’ placement within the upper leg, is how they control travel. The 130mm 26″ Lefty is the same upper and lower as the 100mm 29er Lefty, it’s just these internal bits that limit travel for the bigger wheels.
If you’re curious as to whether you could put a 650B wheel on this, Murray says you could put it on the 29er Lefty. On the 26″ model, you’d be cutting clearance really tight and it’s not recommended. They build in 20mm of clearance for a 26×2.3 tire at the top of the tire to the bottom of the lower fork clamp. That’s under full compression and deflection, so you’d have to hit something really hard, really fast and at an aggressive angle to get the tire that close, but on a 650B wheelset with a similarly fat tire, you’d risk hitting the tire on the “crown”.
Internally, it’s a Solo Air, isolated damping cartridge. The Solo Air tech comes from Rockshox, which they’ve gone with on all 2013 forks, too. Solo Air automatically sets negative air pressure, and it saves about 60g over a coil negative spring. The air spring is at the bottom of the cartridge, the white part in the photo.
The damping controls are in the red part at the top and includes speed sensitive high- and low-speed compression damping circuits. The new Lefty’s have a new alloy oil cap at the top with Durathon glide bearings with a urethane U-ring, which makes the pistons slide faster and easier and makes the system stiffer than with the prior plastic caps…after a break-in period. The urethane U-rings have a tighter seal, and there’s one on each end of the cartridge, plus the new lip seal on the bottom. Service life for the cartridge now jumps from 100 hours to 200 hours. They also have a new damper exchange service for shops to make repairs quicker for riders and easier on the folks in the back of the shop. The new damper cartridge and top cap will also be retrofittable to Lefty’s as far back as 2005.
We had heard rumors the damping characteristics would be changed, but Hannah says they’re the same from last year. It’s just the change in bushings and seals that seem to make them feel firmer at first. We’ll need a long term test to suss out any subtle differences.
For 2013, there are three models: PRB, XLR and Carbon XLR. On the alloy models, the upper is a one-piece unit including the clamps. The carbon model uses a filament wound carbon tube with bonded alloy clamps, and it saves 100g versus the alloy models. PBR uses a push button lockout with external rebound control knob. On the XLRs (carbon model shown above), you get Rockshox’s hydraulic remote lockout button. Retail hasn’t been finalized, but expect them to range from $800 to $1250.
As for “lighter”, the 2013 Lefty’s are the same weight as before, so the improvements were achieved with no weight gain. They’re still lighter than standard two-legged forks by a good margin. While it hasn’t achieved a whole lot of rider adoption, the Lefty For All conversion kit lets you run a Lefty on about any bike. New for 2013 is a tapered specific Lefty For All kit, adding to the straight 1-1/8″ model offered previously. Retail on the kit is $95. Lefty’s will be available in July on bikes, aftermarket will follow later in the year. Parts come from everywhere, but they’re assembled in Bedford, PA.
I rode the new Lefty 29er 100mm on the Scalpel 29 this week, and it’s as precise as ever. It felt noticeably firmer than before, which meant it was a bit rougher over the stutter bumps, but it also didn’t dive through its travel. This could have been as much due to the initial stiction of the new seals on the lower and within the damping cartridge. Hannah says it’ll “loosen” up over time (in a good way, not a flex way). My impressions were shared by pro racer Jeremiah Bishop when we talked to him earlier this year as the first prototypes started showing up. More riding to come!