A Lefty Fork On Almost Any Frame

WHAT: Project321 Lefty Adaptor HOW MUCH: $199 (clamp-on crown) or $90 (bonded crown) WHERE: Project321.com, 559.906.5253

Long before a consortium of companies created the OnePointFive standard, Cannondale was building forks and frames with oversize 1.5 inch headtubes. Their flagship fork, the Lefty, is one of the more distinct forks to reach the market; with only one leg, it has surprising stiffness, and with the help of Manitou, Fox or Cannondale internals, has gone through a variety of incarnations. There are some that believe that a well-dialed, well-maintained Lefty is one of the finer forks out there. I'm one of those people. However, the OnePointFive standard has yet to become ubiquitous - least of all on XC bikes.

Enter the Project321 Lefty adaptor.

As an aftermarket motorsports compary, Project321 has put their aluminum expertise into creating an adaptor that allows Lefty forks (including the newest Carbon Lefties) to be used with standard 1 and 1/8 inch headtubes. While they’ve been doing this for a few years now, they’ve recently released several new versions of the adaptor that sport impressive aluminum workmanship and decreased weight. It's a simple, clever device; the kit is essentially two machined clamp spacers and a steerer tube (for the bonded Lefty models, clamp-on Lefty models include new top and bottom crowns instead of spacers). But does it work well?

I installed a Lefty DLR on a BMC FourStroke, which has a 1 and 1/8 inch headtube. With most bikes, the installation should be relatively straightforward; removing the factory steerer tube from the Lefty is the toughest part, due to a tiny rivet that holds it in place. Once my overwhelming manly force subdued the lone rivet, it was smooth sailing. While there’s not a whole lot of technical knowledge required, take care to slide the assembly together with the headset, crowns and spacers in the right order.

A Project321 adaptor for a clamp-style Lefty fork

As tends to happen with sound products, I installed the adaptor and promptly forgot it was there at all. Having ridden two of the Project321 adaptors for over three months, I can attest that the setup functions well, with no noticeable loss of stiffness and no maintenance issues. A thin coat of grease on the contact surfaces was sufficient to quell any creaking that might have otherwise popped up.

However, it bears noting that if you endeavor to install one of these, you must be prepared for two eventualities. The first is that your beloved Lefty will no longer be compatible with a 1.5 inch headtube without a little legwork.

The second condition of installation is this: many (cross-country) bikes out there were not designed for the stresses of a dual-crown fork; you might be putting the health of your headtube in jeopardy (not to mention your warranty) if you decide to really abuse this setup beyond the intended uses of your frame.

The adaptor clamps come in two sizes: one for stack heights ranging from 5.350 to 5.750, and the second for heights of 5.725 to 6.125. Your $199 will get you a choice of silver or black adaptor, but custom colors are possible for an additional charge. The adaptor for the Carbon (bonded) Lefties (including the new carbon SL) retails for $90.

In sum, the Project321 adaptor is a viable idea for someone who has some minimal bike know-how and a big C festooned on their heart. It might just mean the combination of a perfect frame and perfect fork - one previously thought impossible.