Good performance from suspension systems is the key to make a sled fast. A person can easily add 30 hp to a trail sled, but if it can’t handle a bump or navigate a turn, what good does more power do? We had a Yamaha Nytro as part of our fleet last year. Its 973cc, four-stroke, three-cylinder engine made good power, but its suspension systems couldn’t keep up through the moguls as well as we wanted them to. So we turned to Ross Benson at Hygear Suspension in New York for help. And he delivered.
We got Hygear’s Ultimate Trail Pro shock package from its test sled in March, which gave us several weekends to test the setup on Northern Minnesota trails. Hygear set us up with four shocks, mounting hardware and setup instructions. Up front, each Fox FLOAT shock had two external cells. One cell mounted to the sled’s lower A-arm; it was a hydraulic remote reservoir that offered increased oil capacity to keep the shock cool.
The more interesting cell was a piggyback air reservoir that offered 22 clicks of adjustment. This reservoir increased the shock’s overall air capacity to reduce progression and provide a plusher ride.
FLOAT shocks use air as a spring; Yamaha filled the shocks with about 70 psi from the factory. The 542-pound Nytro ER needs high-pressure “springs” to support its weight and to help prevent chassis roll and push in the corners. The problem with high air pressure is that the shock’s rate of compression becomes too progressive, which makes the ride feel stiff at the mid and bottom of the stroke. But there’s one way to make high air pressure work better: more air volume.
With more air volume, a FLOAT shock can use high air pressures without the harsh characteristics because its compression rate is more linear, or less progressive. Think of it like compressing an inflatable ball.
For example, if a 100-pound person stood on a miniature basketball that has 50 psi in its normal state, its pressure would jump up to 100 psi. But if that 100-pound person stood on a full-size basketball with 50 psi, its pressure would only go up to 75 psi because it has more air volume. Hygear’s reservoirs work under the same principle.
The air cell we used also included an air control valve that allows a larger range of air pressures to dial in the ride and performance even more. The clicker valve affects the rate of air flow between the reservoir and shock body to make them more or less progressive. Turning the screw in restricted air flow and stiffened the ride; turning it out made for a more supple feel.
To understand how this air valve works, imagine a syringe full of air and try to compress it as fast as possible. Without restriction, air easily shoots out of the syringe. But with a finger held against the tip, the air won’t escape as easily. With the shock’s valve nearly closed, it will be hard to compress – like air from a syringe would be with a finger over the hole.
Internal components of the FLOAT shocks and their hydraulic reservoirs were improved over stock, too. The easier and more fluid a shock part moves, the better the damper will perform, so Hygear replaced the stock aluminum internal floating piston (IFP) with an air bladder piston that provides a plusher feel than the metal part.
The floating piston is inside the shock body and separates the nitrogen from the oil. Aluminum IFPs rely on a seal to keep the high-pressure gas and oil separate, but seals can leak and drag inside the shock, which creates friction. The bladder piston is more slippery and conforms to irregularities of a shock body, which are especially common on reservoirs that are secured to the machine with hose clamps. The clamps can distort the body.
The Yamaha Pro Active rear suspension was upgraded, too. Hygear Suspension added a 22-click, compression adjustable reservoir with a dual-rate, coil-over spring to the front track shock. The softer, shorter spring is used to provide a supple ride over smaller bumps at slow speed while the larger spring comes into play with big bumps and high speeds.
In the rear shock, low-speed valving was softened to keep the ride plush at slow speeds and through moderate bumps. High-speed valving in the shock’s reservoir was boosted to reduce bottoming.
Instructions said to move the torsion spring carriers back about one inch on the rail. This increased each spring’s rate of compression at bottom out because the new position reduced their mechanical advantage.
This complicated stuff made our Nytro a much more capable bumps sled than stock.
Going into this product test, we were most concerned with improving the Nytro’s rear suspension because we thought its front end worked fine. Before the suspension upgrades, there was a disconnect between the front and rear suspensions. The Deltabox front end was firm like a cross-country race sled, but the rear end was cushy. We crashed through the Pro Active’s travel like it was a falling-rate design.
After installing the upgraded FLOATs, we realized how much better the sled performed. The suspension was now bold enough to suck up big hits and corner relatively flat.
We found Hygear’s “stock” FLOAT settings, which were smack-dab in the middle at click No. 11, too firm, so we backed out the screw to allow easier airflow. The supple front end was smooth and steady through chatter. Handling was more precise and the sled felt tighter.
The machine’s ride quality was greatly improved with Hygear Suspension’s changes and the chassis was more controllable. Our confidence over 1-foot moguls was improved tenfold. We used to cringe and hope for the best if we suddenly came upon a row of bumps. After the mods, we just hit ’em.
Freeville, New York