Trek Top Fuel 9.9 Race Shop Limited 2018 Orange/ Black MTB Bike

RE:aktiv

Better flow, better ride

Any mountain biker understands the bliss that comes with zeroing in on the trail and nothing else. No outside distractions—including inconsistent suspension performance. That’s what it’s all about. More flow is RE:aktiv’s greatest gift.

You’ll accelerate as aggressively as you can without losing efficiency to pedal bob. You’ll confidently take gnarly, technical lines knowing that your rear shock will provide an instant, supple response. You’ll feel the difference of a shock that immediately transitions from soft to firm as you fly out of corners. You’ll experience the beauty of simply being in the moment.

RE:aktiv does exactly what you need it to do, exactly when you need it to. No more adjustments on the trail, no more choice between efficiency or control—pure confidence and enjoyment no matter what the trail brings you.

From the racetrack to the gravity park

What do Formula One and mountain biking have in common? Both sports put extreme demands on suspension systems, requiring the utmost stability and control in straights and corners, coupled with the capability to instantaneously respond to sudden bumps. For years, the ultimate challenge for mountain bike suspension engineers has been designing a shock that is firm and supportive while pedaling and in the corners, but capable of being plush and yielding to handle sudden impacts without knocking you off your line.

RE:aktiv is the most efficient technology to do just that. What inertia valves attempted for years has finally been realized. The RE:aktiv ride is firm under pedaling efforts, but provides a smooth, instantaneous transition to plush control, giving you confidence to ride your bike as it should be ridden. The key point is that RE:aktiv gives you the best of both worlds all the time. It is not two settings, but an integral part of the rear shock’s design that ensures you’re ready for any obstacle the trail throws your way.

Developed in collaboration with the experts at Penske Racing Shocks, the global leader in custom design for auto racing suspension, and FOX, RE:aktiv is the result of the best minds in suspension design seeking out the most refined damping technology mountain biking has ever seen.

Regressive Damping & Formula 1

RE:aktiv’s intuitiveness is a product of its regressive damping system. Proven in the demanding crucible of F1 circuits, regressive damping is dynamic and versatile. Most mountain bike suspension systems employ progressive or digressive damping, which simply do not respond as efficiently to a variety of obstacles. Such systems also have a difficult time transitioning from the active, support and control suspension action required in corners to the pedaling efficiency necessary to regain speed on straightaways or less technical sections of trail.

When Trek’s engineers realized how effective this technology was in Formula One—where drivers encounter bumps and fly into corners at 200 mph—they knew it had an application to our sport. Penske Racing Shocks is the best, so a partnership was formed and prototypes were developed. FOX and Trek brought the expertise needed to scale up Penske’s custom designs, and RE:aktiv was born.

Regressive damping is the most adaptive

Effective damping is a vital component of suspension performance. Damping makes your ride rigid when on the pedals, but it stands in your way when confronting obstacles or ripping through corners.

Regressive damping works when it should, and only when it should, because its engagement is sensitive to shaft velocity. What affects shaft velocity? Most rider inputs, like pedaling, produce low velocity, whereas most environmental inputs are the result of encounters with eruptive shapes, and result in high shaft velocity. With RE:aktiv, inputs that produce low shaft velocity do not affect performance but a threshold exists where anything that exceeds it immediately and dramatically changes the function of the shock. A sudden increase of shaft velocity—or how quickly the shock is trying to compress—opens the suspension up and allows for a supple and controlled response. It’s like having two different shocks on your bike.

Normal rider input cannot produce enough velocity through pedaling to open the shock, which is the basis for RE:aktiv’s ability to distinguish pedaling from environmental inputs that require engagement of the suspension. When abrupt obstacles are encountered, the shock gets out of its own way. The process reverses as quickly as it begins, meaning you don’t lose it on the obstacle but don’t sacrifice efficiency in the transition either. The speed of this transition is what gives RE:aktiv its unique feel—one that riders have been seeking for years.

No hesitation

For years, inertia valves provided damping in mountain bike suspension. While this technology is very good at keeping closed and providing efficiency, it is not successful in adapting to changes in the terrain.

RE:aktiv was designed to address the primary drawback of these systems—they require too much input to engage. Because inertia valves respond to g force, the shock often fails to open up when it should. Your shock may not fully engage until the second or third hit of a techy section, and you sacrifice control and feedback in the meantime.

The problem persists on the other end of the obstacle or corner, where a lag period occurs before the shock realizes it is no longer needed and the damping function reengages. Essentially, inertia valves work, they’re just slow to recognize what’s happening around them. They become easily confused in off-road applications because they don’t easily identify different inputs, and don’t know whether to close or open on variable terrain. Simply put, other technologies lack the intuitiveness and immediate response that RE:aktiv provides.

Set and forget

RE:aktiv was designed to complement existing suspension settings, such as climb and trail modes. RE:aktiv can function effectively in all three settings, allowing you to simply pick the proper setting and let her rip. Wouldn’t it be nice to no longer interrupt your flow to flip between suspension settings during a ride? It simply makes the shock better all the time.