What About Full Suspension Mountain Bikes?
Full suspension mountain bikes make lots of sense for lots of people. Rather than asking your body to absorb the worst of rough, rocky terrain, your bike's rear shock takes the abuse for you. If you have chronic back or neck aches, a full-suspension bike will allow you to ride further than you ever thought possible. Riding full-suspension is similar to having a tank you can barrel over terrain rather than having to finesse your way through it. My motto? Just run over it! Hmmm...I wonder if that would work with some of the people I've dated.... Full-suspension isn't just some passing fad -- it's pretty darn unbelieveable how much more fun riding off road can be on a full-suspension.
Let's kill off a myth here. Some people think full-suspension is just for going downhill. Hardly. You get the benefit of having extra traction for going uphill. The rear shock keeps your rear wheel on the ground, so rather than bouncing up rocky climbs, your rear wheel digs in and lets you spin to the top. Cannondale sums up the full-suspension experience quite nicely: "non-stop traction whether you're climbing, holding your line, or carving turns. You're controlling the ride, not merely surviving it."
I like what's known as "fully active" rear suspension. This basically means your seat, crankset and bottom bracket are on the main triangle of the frame. Whether you're seated or standing, you always keep your body weight on the frame, allowing the rear suspension to stay active at all times. Your rear shock is free to compress and rebound without restriction. If your saddle, crankset and bottom bracket are attached to the rear swingarm of the frame (known as an "unified rear triangle" design), when you stand out of the saddle virtually none of your body weight is over the frame, thereby inhibiting the swingarm from activating. Think of it like this: when you stand on an URT bike, your rear shock disappears. This creates one major problem on technical descents you spend so much time out of the saddle using body english to steer the bike, you end up losing your rear suspension when you need it most. The only situation when an URT design is advantageous is when you're sprinting out of the saddle. I spend lots more time going downhill than we do sprinting Tour de France-like to a finish line, so I'll take the fully active bike any day.
Let's talk about a few full suspension bikes just for examples...
The Specialized FSR uses the most highly regarded rear suspension design out there the four bar Horst linkage design. Why do a half-dozen of Specialized's competitors pay them an annual licensing fee in order to use the Horst linkage design on their own frames?
1. It's fully active. Its 3" of travel is responsive enough for small bumps, yet beefy enough for the big hits. There are rear shocks out there with more travel.
2. It's fully independent. More so than any other rear suspension made, your pedal stroke won't cause the rear shock to engage, or vice-versa. How? It's all about dialing in the pivot placement within the four-bar system.
3. It's fully functional. To really work well, a suspension design has to last for years with a minimum of service. The sealed pivots in the FSR linkage won't develop lateral slop over time.
The Cannondale Raven is an engineering marvel. It's made out of a super-light magnesium spine wound up with thermoplastic carbon fiber skins. The spine handles the direct force of impacts, while the carbon fiber skins resist torsional loads generated by pedaling forces. The Raven doesn't flex, so you won't lose any handling precision. It weighs 4.7 lbs, over 1.3 lbs lighter than the 1st-generation Raven. The Raven uses Cannondale's fully active Super-V design with a lightweight CAAD4 rear swingarm. Is it a cross-country thoroughbred? No. But no other full suspension bike delivers the Raven's plushness and comfort in rough off-road terrain.
Headshok Front Suspension
· Nothing in mountain biking has gone through more technological change over the last ten years than front suspension. The first several generations of mountain bike suspension resulted in telescoping forks that were little more than simplified, slimmed-down motorcycle forks. They were primitive in every way: they didn't offer much compression travel, they bottomed out all the time, they required constant upkeep, and they had a unacceptably high failure rate. Seal-blowing, leak-prone hydraulic-sprung systems were considered cutting edge for all too long. Thankfully, the internals of these forks have evolved over time. Nowadays oil has been replaced either by air, or by coil springs and urethane bumpers. These new systems are more responsive to small bumps, and they're more resistant to bottoming out. They're lighter, they offer more compression travel, and you can ride them longer before having to perform routine maintenance.
· There is still bad news to report, though. Even though suspension fork internals have evolved, the external structure of the suspension fork has remained virtually unchanged. There are two main pieces to the body of a suspension fork: The lower legs and the stanchion tubes (the upper legs). When your bike hits an object, your fork compresses because the stanchion tubes slide downward into the lower legs. All that holds these two pieces together is a 0.5" tall nylon bushing pressed into the upper lip of each lower leg immediately below the accordion-like shock boot. This design is problematic for two central reasons:
(1) There's only so much abuse a tiny ring of nylon can endure before it begins to deform. Given the enormous force behind your typical impact on a mountain bike ride, it should come as no surprise that over time these nylon bushings ovalize. Once the bushings ovalize (and they always do), the detrimental effects are easily noticeable. It feels like you have loose headset bearings since your fork's lower legs can rock forward and backward independently of the stanchion tubes. Because of this independent leg movement, your bike's handling becomes sloppy and unpredictable. To make matters worse, ovalized bushings make the internals of the fork more prone to contamination. As your stanchion tubes become contaminated, they won't slide smoothly. Again, your fork will begin to act unpredictably.
(2) The impact force when you hit an obstacle is almost never directed squarely upward into the fork legs. The impact generally has some side force to it, putting more demands on one fork leg over the other. In short, one leg wants to compress more than the other. Your bike's propensity to hold its line in these moments deteriorates. Even though a suspension fork is designed to enhance your ability to control your bike, in this all-to-frequent situation the opposite comes true: you lose some of your ability to anticipate where your bike is tracking.
· An obvious question arises: If the cause of these problems is the ovalization of over-stressed bushings, then why not make the bushings taller? By allowing for more shared space between the lower legs and the stanchion tubes, wouldn't this prevent bushing ovalization? In theory, that seems to be a great solution. The main problem, though, is that if you use a taller bushing, you create so much friction between the lower legs and the stanchion tubes that only the most violent impacts would cause the fork to engage. This static friction, known in the bike world as "stiction", is still one of the greatest problems with suspension forks. Even with a short 0.5" bushing, suspension forks still show a consistent unwillingness to engage smaller, less dramatic impacts. Beyond this, a taller bushing wouldn't eliminate the fork's propensity toward uneven leg compression.
· And this is where the story of the Cannondale Headshok front suspension system begins. It shares the more advanced internal features of leading suspension forks, while offering a tremendous advantage in terms of durability and handling. The Headshok's internals are quite similar to those found on high-end suspension forks. You get 70mm of travel using an ultra-light airsprung system. You can adjust the compression characteristics of the suspension by adding or removing air pressure from the shock. You can dial in the perfect ride quality, whether you weigh 110 or 310 lbs. It's a hydraulically-damped system, too, so your rebounding always feels smooth and controlled, no matter the force of the impact. An added bonus is that you can lock the shock out completely while you ride. If you're riding on paved roads, and especially when you're climbing smooth fire road trails, a front suspension fork acts unnervingly like a pogo stick. A fork's tendency to bob wastes energy and ruins your climbing rhythm. You can lock out the Headshok by flipping a dial on your stem. Other forks have partial lockouts, but the Headshok is the only suspension system with a complete lockout.
· What really sets the Headshok apart is its external structure. The Headshok
operates through the use of a telescoping steerer tube that travels inside the
headtube of the frame itself. Unlike a suspension fork, the fork legs in a Headshok
system are completely rigid. This is a simple solution to the problem of independent
fork leg compression. With a Headshok, the fork legs and the front wheel always
travel in unison, giving it unparalleled tracking performance.
· The steerer tube of the Headshok and the headtube of the frame
share over four inches of space. Shims take up every millimeter of the
gap between the two tubes. Unlike the nylon bushings in a suspension
fork, these shims won't deteriorate over time, so your tracking precision
will never be compromised. Beyond this, the steerer glides on four towers of 22 roller bearings, giving it stiction-free responsiveness to small bumps and repetitive
washboard bumps. No suspension fork can match the Headshok's sensitivity to slight hits. The durability of the Headshok is second-to-none. The internals are less exposed to mud and grime for two reasons: (1) They're higher up on the bike, (inside the headtube of the frame, not inside the fork legs), so muck from the trail has to fly further to work it's way inside the suspension. (2) The Headshok is sealed up by a shock boot that won't slip and by a pair of massive cartridge bearings that simply won't admit contamination. This means more hours of riding without having to perform maintenance.
What's the very latest in Headshok technology? It's a brilliant solution to
an age-old suspension quandary. Riders have always searched for the
added performance of a long travel suspension fork (100mm of travel)
without having to suffer excessive fork weight and flex. The answer?
The revolutionary HeadShok Lefty fork. It features a single telescoping
blade that dramatically reduces weight while delivering 100mm of travel.
The Lefty weighs 3.7 pounds, including axle, making it very possibly the
lightest long-travel fork anywhere.
Like other Headshok forks, the Lefty has four corresponding flats on both
the oversized aluminum stanchion and slider, with 88 needle bearings rolling
easily between the flats for unparalleled response to small bumps.
The Lefty's dedicated CODA hub features sealed cartridge bearings and
a weight saving tapered chrome-moly axle. The axle has a burly 25mm
outside diameter on its left (supported) side for strength, and a slimmer
15mm o.d. on the unsupported right-hand side where the loads are
significantly less. For easy wheel removal, the hub is outfitted with a
self-extracting bolt that draws the wheel off of the axle as the bolt is
loosened. The new disc brake-specific fork is air-sprung and oil-damped.
An on-the-fly lockout control temporarily deactivates the fork
(for bob-free sprints or road rides to the trail-head), and an
on-the-fly rebound adjuster lets the rider match the Lefty's performance
to the terrain.
For 2001 Cannondale introduced their ELO for the Headshok Lefty.
The Electronic Lock-Out feature is activated by a small handlebar-mounted
push-button that activates and de-activates the Lefty. Compatible with all shifters and brake levers, the lock-out button can be mounted to either side of the handlebars for right or left-handed operation. The E.L.O. takes less than a second to activate - less time than it takes to operate any manual lock-out - and it features a one-way valve that allows the Lefty to re-extend if it's activated when the fork is compressed.
A red LED on top of the Lefty's stanchion provides a quick visual indication when the fork is locked-out. The key to E.L.O. is a miniature Swiss motor located near the top of the Lefty's oversized stanchion tube. The lightweight motor runs off an easily replaceable 9-volt lithium battery, and it closes and opens a valve to either lock the fork out or resume normal suspension operation. Along with E.L.O., selected Lefty's also feature a new weight-saving titanium axle that trims 91 grams from the fork's weight. And since the push-button, battery and motor are the same approximate weight as the manual lock-out knob they replace, the ability to keep both hands on the handlebars while locking-out the fork actually comes with an overall weight reduction.
