Out of the box: Fox’s Terralogic fork technology


Call it fate. I recently purchased a Santa Cruz Highball frame and needed a fork to complete my build, and while I searched an email was forwarded to me from Fox looking for a tester for this fork.

The fork happens to be a Fox 32 Float 29, 100mm FIT Terralogic model, and yes, I’d like to test it. This model is available with either a 9mm drop-out or with an included 15mm thru-axle, which I opted for, and with either a tapered or 1 1/8” straight steerer. Kashima coated uppers, Terralogic threshold, rebound, and an air spring with updated damping for 2014 are all included.

The Terralogic technology was first introduced in 2004 and before that Fox partnered with Specialized to develop the Brain for its full-suspension rigs. If you’re not familiar, here’s the basics: when Terralogic is engaged, the fork rides as if it were locked out. Stand up, mash the pedals, pump the bars back and forth and there’s very little movement in the fork. When you hit a bump, the force from below activates the suspension by pushing the lowers up. As the lowers rise, a brass mass, which seemingly moves but really stays in place relative to the fork, reveals a piston for the oil to flow through and the suspension to become active. The amount of force needed for activation is controlled by a threshold adjuster. A return spring eventually pushes the brass mass back into place when the trail smoothes out, restricting again the flow of oil.


In 2007, the Terralogic models were discontinued, then revamped and reintroduced to the market for Fox’s 2011 line. What did they change? On the older models, it took a hit to activate the suspension, so the first encounter was always harsh. The return spring was also too heavy, which compromised performance.

In the 2011 models and after, including this one, the brass mass is twice as heavy and the return spring lighter, so with the first impact the suspension becomes active. The lighter spring also allows the brass mass to “move” more easily, so smaller bumps and low speed compression greatly influence the performance.

I’ve got about six rides on the fork, and so far I’m wondering why I didn’t go the Terralogic way sooner. I love it and it fits my riding style, plus I don’t need to keep flipping a lock out switch.

Will it work out in the long term? Look for a full review in an upcoming issue of Dirt Rag.