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The problem with being an aging mountain biker is that while my skills may improve slightly, the rocks don't get softer with each passing year. I've come to accept, for example, that I'll never clean up the Teacup Trail in Sedona when I ride from the west side of town to the fun, gentle trails like Adobe Jack around Soldier Pass. But I stupidly keep trying, fractures be damned, because what's also true: year after year, the bike's suspension keeps getting better.

Garage mechanics have been tinkering with bicycle suspension since around 1888. Full-suspension bikes, equipped with a front fork and a smaller rear shock, became widespread in the 1990s, when brands like Specialized, Trek and Santa Cruz took the results of their tinkering out of the garage and into the light of day.

I bought my first full suspension mountain bike, a Santa Cruz Superlight, in 2000. With 100mm of travel (maximum suspension distance compresses while absorbing shock) in the rear shock and 120mm of travel up front, it gave me the confidence to ride lines through the rocks of New Mexico that I wouldn't have dreamed of riding on my Specialized Stumpjumper hardtail, which only had front suspension.

Today's full-suspension bikes have so much comfort that the world's best downhill racers can safely crush events like Red Bull's Hardline Tasmania, a course that combines brutal technical features with massive jumps, because they have front shocks with 200-220mm of travel.

I've ridden a full-suspension bike for the past three decades, and I've been testing bikes for WIRED since a poorly planned trip to the Mojave Desert in 2014. But there are experts far greater than me when it comes to explaining how suspension works. So I asked Vernon Felton, director of product at Canyon, former editor-in-chief of Pinkbike, and former editor-in-chief of Bike magazine, to explain it to us.

What is suspension?

“Mountain bikes are designed to take you over mountains…and all the rocks and roots that stand between you and your destination,” says Felton. Sure, he adds, you can mountain bike over all kinds of obstacles without a suspension fork or rear shock, but "doing it, without the aid of suspension, requires a lot of very skillful body English and takes a toll on your body and your energy level."

How does it work?

"Suspension almost always consists of a spring (made of a metal coil or sealed air canister) that compresses when your wheels encounter rocks, roots, ruts, etc., and some sort of 'rebound damper' that slows the spring as it bounces back into its unloaded form," says Felton. “Without a shock unit (or “damper”), your bike would bounce uncontrollably like a pogo stick every time you hit a big enough bump.”

Better bike brands, he adds, work tirelessly with companies like Fox Racing and RockShox to "adjust these spongy elements so that they work optimally with the bike company's frame design. The bike's weight, style, and precise linkage placement all affect how the suspension works; therefore, companies use specific 'tweaks' to optimize the flow of oil inside the shock and change the feel of the suspension."

Why do you need oil? When a bike hits a rock, the suspension, whether a coil spring or air spring, is compressed. At this point, a piston forces oil upward through small or large openings and valves, depending on the speed of impact. This creates resistance, also called damping, which controls how quickly the suspension compresses. Once the obstacle is cleared, the shock absorber “bounces” or returns to its original length. The “melody” of a shock essentially controls how quickly this process occurs and, to some extent, how much impact the shock, rather than your arms, legs, back, neck, shoulders, and every other part of the body, will absorb.

How does suspension differ between a cross country, trail, enduro, and downhill mountain bike?

“Ultimately, all suspension is designed to do the same thing: help you climb rough terrain with greater ease, speed, comfort and control,” says Felton. But different styles of mountain biking, as well as widely varying terrain, require different suspension styles and levels.

“A cross-country racer is looking for the lightest, most efficient bike,” says Felton. "They place a high value on how quickly the bike allows them to climb big mountains. As a result, off-road suspension tends to have fewer inches of travel, and the suspension may feel firm to a more casual rider."

Trail, enduro and downhill riders, meanwhile, says Felton, "want to maximize speed on the toughest descents and so typically equip their bikes with suspension that offers greater suspension travel and a smoother, more forgiving ride quality."

Is e-bike suspension different?

E-bikes are “invariably” different, Felton says, because you add a motor and battery to the mix, which impacts suspension performance. Likewise, the motor introduces a surge of torque through the pedals which also impacts the suspension (often causing the shock to compress even when riding on smooth terrain).

To compensate, companies like Specialized custom tune suspension forks and rear shocks so that they perform optimally despite the extra weight and power added to the mountain bike mix.

There are, Felton adds, some specially modified suspension forks that feature sturdier components designed to keep the forks from flexing too much given the system's greater weight and riding speed.

What should consumers look for in e-bike suspension?

“Most of the weight of an electric mountain bike comes from adding a battery,” says Felton. Batteries are getting lighter by the day, but a typical electric mountain bike battery can weigh around 7 to 11 pounds. The bigger the battery, the more fuel cells it contains… and the more weight added to your bike.

“If you want to make your electric bike lighter, start by finding a bike with a smaller battery. This can easily reduce the overall weight of the bike. Just understand that a smaller battery also means fewer miles per battery charge,” says Felton, “so you need to weigh the importance of weight versus miles per charge (or “range”).

Ultimately, e-bikes help you ride further and faster. So, look for the best quality suspension possible. But unless you're a master garage DIYer, you might want to stick for now to an e-bike that features front and rear shocks created by the forefathers of suspension.

“You want the softest feel, least flex, and best durability when doing long, high-speed rides,” says Felton. “Look for suspension from brands like RockShox, Fox, Cane Creek and Marzocchi. These brands have been making world-class mountain bike suspension since the 90s.”

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