ezryde suspension

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Snowmobiles are being reinvented daily at aftermarket performance shops.

While the Big 4 deliver fine products, it's often the aftermar-keteers who stretch beyond the norm to a "wow" level. Great Lakes Sound & Vibration (GLSV) Inc. is one of them, an engineering consulting firm in Michigan's Upper Peninsula that specializes in acoustic, vibration and shock reduction. Its latest, the EZRyde rear suspension, redefines control for both trail and mountain sleds.

The design got its start when GLSV's owner and avid snowmobiler, Steve Polakowski, realized rear suspensions could be much better. GLSV had executed an array of noise and vibration contracts for the snowmobile industry along with some shock and isolation projects. So it seemed a natural extension to tackle suspensions.

We first saw the EZRyde last February at our annual Mountain Mod Ride when Max Maxedon of Tri-City Performance introduced us to it and to Polakowski. We noted how simple this suspension is. It offers improved deep snow performance, traction, weight transfer, side hilling ability, handling/control and wicked bump absorption. All of this while cutting about 15 lbs.

Maxedon and Bret Rasmussen, owner of Snowmobile Research Services, have been using it and have been wowed by it.

Last winter the new rear suspension made its debut on the Rocky Mountain Snowmobile Hillclimb Association (RMSHA) circuit too. Racers using it included Rick Ward, Shane Hart and Dennis Durmis. Ward won the Pro Master Mod in all events he entered with the EZRyde. He also posted the fastest time of all the sleds at the World Championships at Jackson Hole.

Polakowski says EZRyde is de-signed to function like a motocross bike's swing-arm suspension, making a snowmobile feel motocross-like. Shock damping, spring rates and control bumpers were designed to provide function in different ride regions.

More travel
In simple terms, the longer it takes an item to come to rest, the lower the shock levels. EZRyde uses more travel during a broader range of disturbances along with controlled bottoming to maximize absorption time. The result is superior performance and ride quality.

EZRyde provides a template that's used to mount the suspension. The template is a ¼-inch thick aluminum sheet with CNC placed holes for locating driveshaft and front and rear mounting holes. This may seem like overkill but it ensures shock angles are optimized, the attack angle is correct and weight transfer is properly set. This also cuts install time and assures critical dimensions are correctly set.

Our main image (opposite page) shows the suspension in a 144-inch Polaris tunnel, it also contains an inset that shows track attack angle. This illustrates how the track angle changes with rear suspension displacement.

The slider joint, a new term (patent pending), is at the bottom of the arm and is designed to allow the skid's rails to move rearward in a slot. Both skid rails also pivot about this joint. The joints are located at the end of the arm, which allows the entire lower skid to move rearward whenever the suspension is displaced. Displacement occurs during acceleration/deceleration, bumps and on uneven terrain. You can see that suspension displacement causes the track attack angle to decrease. It also yields greater tack to ground contact area and helps traction.

Benefits
Just looking at the skid rails you might think they're under-designed or fragile. However, their benefits exceed simple weight reduction.

These skid rails are flexible due to alloy selection and an extrusion process where aluminum billets are pushed through a die to form the rail cross-section. There also is in-house finish cutting and bending. The addition of a scissors-type action between right and left rails simulates the effect provided by EZRyde's twin track suspension. It enables the track to better conform to varying terrain. Flexibility also reduces moments that resist turning or "up righting." The result is superior traction and maneuverability.

Extensive structural fatigue and load path analysis yielded a shock attachment design that may not be obvious or familiar because the front and rear shocks attach to the arm at or near extreme ends of the swing arm. The configuration minimizes armloads, yields lighter components and offers better durability. This strategy enabled GLSV to design the arm using aluminum, an industry first.

We believe the EZRyde is well on the way to setting a new benchmark for rear suspension weight while not sacrificing durability and reliability.

Understand that static weight was only one design criteria. GLSV also tried to minimize in-field and un-sprung weights. In-field weight is a measure of how much snow is retained in the suspension. Unsprung weight is simply defined as suspension weight not attached to the chassis.

GLSV scrutinized every component for overall weight and unsprung weight. This includes mounting of the Compression Dampening (CD) adjust reservoir to the tunnel's underside. The unsprung weight for the EZRyde 144-inch is just 26.5 lbs.

Why is unsprung weight so big?

Reaction forces of the track and skid rails caused by uneven terrain are transmitted by the suspension to the chassis. The lower the unsprung mass, the smaller the forces exerted on the chassis and driver.

Ride quality and mechanical loads are closely related to the ratio of unsprung mass to sprung mass. EZRyde reduces the unsprung weight by about 10 lbs., not including snow pack added as in-field weight. This results in a 27.4% improvement in the unsprung to sprung weight ratio.

Adjusting the EZRyde is simple. The rear spring pack is composed of a main and a tender spring. These are coupled with an adjustable crossover system that enables you to modify the crossover point without changing rates. Changes in the main and tender spring affect initial rate, final rate and crossover point.

Spring and damping changes are simple too, as either or both shocks can be removed in minutes without removing the entire suspension. Weight transfer is adjusted via a series of front suspension mounting locations prescribed by EZRyde. The rear shock comes standard with a 16 position CD adjust clicker.

Finally, preload can be added to either or both front and rear springs. Do this by simply turning a standard preload adjustment nut. EZRyde plans to publish full rear spring pack tuning tables on its Web site.

EZRyde hit the mark by providing a skid that offers reduced weight, improved performance, simplicity, innovation, tunability and durability.

For more info contact: EZRyde at www.ezryde.com; Max Maxedon at Tri-City Performance, 801-298-8081; or Bret Rasmussen at Snowmobile Research Services, 208-221-4294.

-Steve Polakowski contributed to this report