Dirt bikes have come a long way since those early rides of the 1970s.
Like cars, today's dirt bikes bear little resemblance to their 40 year old siblings that once dominated Motocross tracks. Sure, their outward appearance looks similar. Two wheels, a seat, handlebars, foot pegs and drive chain. But a lot more goes into making the modern day dirt bike the beast on the track or off-road and much if it starts with the suspension.
The suspension evolution, as Tom White, who owns and operates The Early Years of Motocross Museum in Villa Park, CA, calls it, gave one of the biggest changes to dirt bike allowing the machine to race faster and tackle larger scale obstacles.
Vintage Dirt Bike
In the beginning, perhaps around the turn of the 20th century, dirt bikes made their presence known. Dirt bike racing, or motocross as it was yet to be called, can be traced back to Europe in the early 1900s. In those days, there wasn't much to the suspension. Rather, a rigid frame greeted riders who braved the off-roading lifestyle. Suspensions finally gave riders relief in the 1930s and the more advanced swinging fork rear suspension arrived in the 1950s, even before equipping the majority of standard street motorcycles.
In 1975, the Yamaha YZ250 ushered in a new era of suspension that most other manufacturers quickly followed - the Monoshock.
The Monoshock Suspension - Photo: Courtesy Yamaha Motorsports
This single shock motocross bike placed the shock below the seat and allowed better riding over rough terrain. Most motocross bikes at the time gave three to four inches of suspension travel, the monoshock offered seven inches front and rear. This revolution in the dirt bike suspension sidelined the twin-shock system and snowballed to where by 1980, riders enjoyed 12-inches of suspension give. It is safe to say that without this modern feature, today's Supercross and Motocross tracks would like quite tame compared to the larger more technical and obstacles riders tackle.
A 1980 Honda RC250 Concept Bike
Yamaha also introduced the rising rate linkage rear suspension but the company lost ground to an innovative design that helped push forward the suspension evolution.
Suzuki one-upped Yamaha in 1981 with the "Full Floater" single shock rear suspension introduced on the RM125. The Full Floater suspension implemented the use of rising rate linkage in the suspension that most manufacturers were already incorporating into their designs. The difference with Suzuki's version was the complexity in that it used a floating linkage on the shock's top and bottom and a set of pull rods connecting the system to the swingarm.
Ad for the Full Floater - Photo: Courtesy SuzukiCycles
The Full Floater system offered a flexible system, yet firm when needed, and handled bumps with ease. This suspension proved quite popular and defined Motocross in the early 1980s. As great as it was, it's overall complex design proved to be its downfall and just five years later Suzuki dumped it. However, many believe the Full Floater opened the door for today's modern suspension systems.
The suspension that handles the dirt bikes Ryan Villopoto and James Stewart ride are engineering marvels. Two components make up the modern suspension: springs and dampening.
The springs in the rear shock are visible, but housed in the fork tubes for the front shocks. Damping, or compression damping and rebound damping, controls the energy absorption when the shock is compressed and then released, usually with oil.
James Stewart's bike uses the triple chamber Showa forks - Photo: Courtesy VitalMX
Suspension damping is controlled through the use of "clickers," essentially small screws that adjust the compression and rebound. If compression is too soft, you'll have a tendency to bottom out, too stiff and you'll replicate what the sport's forefathers rode on so many years ago. If shocks "rebound" too fast after compression the bike tends to kick, but too slow and you won't be ready for the next bump, especially crucial through whoops.
Ivan Tedesco Sporting the WP Air Shock - Photo: Courtesy Transworld Motocross
Air shocks offer the latest advancement in suspension technology by replacing the now traditional oil fork with air forks. The pneumatic spring fork (or air fork) ditched the coil spring and dropped nearly two pounds of weight, reduced friction and oil contamination, and offered better bottoming resistance and easy customization using a basic air pump.
Manufacturers naturally gravitate towards the next best thing, so just like the swinging rear fork suspension of the 50s and the monoshock of the 80s, most dirt bike companies now offer air shocks. In 2013, Honda made standard the air shock on all CRF450Rs.
Coil Spring vs. Air Fork
Someday air shocks will be "vintage" replaced by the next engineering wonder designers dream up. In Motocross, lighter is better so whatever invention makes tomorrow's dirt bikes, expect it to be lighter, agile and perhaps more responsive to the rider without the need for adjustments.
Until then, braap on with whatever suspension keeps you on two wheels.