Snowmobile suspension kits are some of our favorite mods to test because they often produce impressive gains in ride and handling. With Hygear Suspension pushing its Sport X package for Ski-Doo REV-XPs last fall, we ordered one for our 2009 MX Z TNT 600 E-TEC in December.
The Box Contained…
Hygear didn’t ship us the suspension package until February. Owner Ross Benson says he won’t sell a shock setup to a customer until testing with the machine has proved the setup will work. All sleds are different, and what works in one snowmobile might not work in another, he says.
When our box of shocks finally arrived, it included revalved front suspension shocks with progressive, dual-rate Twisted springs and new bottom-out bumpers on the shafts, which added about one-half inch of travel.
The rear end gained a reservoir with 22 compression clicks on the revalved front-track shock with dual-rate springs; the rear shock was also revalved with a clicker reservoir. All base shocks were stock Kayaba aluminum dampers that were original equipment on the 2009 MX Z TNT.
The Twisted spring kits on the Sport X package are adjustable. The small tender spring affects vehicle ride height through adjustment of the threaded collar. Crossover spacers between the tender and main spring affect the spring set’s progressiveness, or firmness. A wide gap between the springs is less progressive and will give a softer ride than a narrow gap.
Hygear uses a rubber bladder inside the reservoirs instead of an aluminum damping piston. Unlike an aluminum piston that slides inside the cavity, the rubber piece remains stationary as it’s squeezed like a balloon during shock compression and rebound, so there’s no friction. It also forms a better seal to separate the oil and nitrogen within the reservoir because the flexible bladder forms to the inside of the reservoir. This is especially important when a clamp is used to fasten the reservoir to a suspension rail or shock because that can distort the body’s shape and affect piston movement.
How Did It Work?
We installed the shocks and confirmed that both front and rear ride heights were set according to Hygear’s instructions. On the trail, the suspension package helped our MX Z corner flatter and faster, but the shocks felt too firm — especially in the front suspension. We softened the compression damping in the rear shocks with a few clicks on each rear shock, which made the skidframe more comfortable and compliant over bumps.
Hygear’s Sport X instruction manual says that springs control ride height and position in the suspension travel; shock valving is used to control bottoming resistance and ride comfort. So, without external adjusters on the front shocks, we sent them back to Hygear because the front end bounced off of bumps rather than absorbing them. The rework only took three days, including shipping.
The company softened the low-speed compression valving, which allowed the shocks to stroke farther into their travel – this made for a noticeable improvement in performance. The sled stuck to the ground rather than deflecting off the bumps. Not only was the sled more comfortable, but also we could ride it faster knowing the suspension would compress rather than bounce.
Winter Is Too Short
With late delivery and snow running out last spring, we didn’t get to spend as much time riding and playing with the suspension package as we’d hoped. Nonetheless, 500 miles of use proved it was a valuable upgrade. But with more time we could’ve experimented with different spring spacers and perhaps found the ultimate ride and handling. The package retails for $1,274.99.