It’s here! It’s really here! The long-travel snowmobile suspension revolution is really here! Oh sure, there was the Arctic Cat Trail Cat in 1979 and the Ski-Doo Blizzard 5500 MX in 1981, but those sleds suffered from high centers of gravity, narrow ski stances, poor shock absorbers and primitive design geometry.
The current long-travel wars seem to have been touched off by the incredible success of FAST Inc.’s M-10 suspension design. For 1996, Polaris, Ski-Doo and Yamaha all have long movement suspension systems available and Arctic Cat offers their Extended Travel Tunnel (ETT) on their 1995 ZR 440.
XTRA, XTRA Read All About It
Polaris was the first manufacturer to offer a new generation, long-travel suspension system. A handful of XLT XTRA models produced in 1994 got people talking and trying out the new concept. A completely new design was introduced on the RXL and XLT XTRAs for 1995 and for 1996, Polaris has two long-travel designs aimed at different applications, the XTRA-10 and the XTRA-12.
The XTRA-12 is, without question, the plusher riding of the two long-travel designs from Polaris and is found on the Indy Classic, Classic Touring, 500 ER, XLT, XLT Touring, XLT Special and the RXL. These models are also equipped with Polaris’ XTRA-12 front suspension package.
The track suspension design offers 10.2 inches of vertical travel (measured from the compressed bump stop on the rail to the torsion spring on the cross shaft.). The ski suspension delivers 9.6 inches of vertical travel for the longest movement OEM package in the snowmobile industry. To help maintain stability with the higher riding system, the ski stance on the XTRA-l2 equipped models has been stretched out to 42.5 inches. Geometry similar to the XCR’s has been used, along with shorter radius rods, to reduce ski scrub and keep the overall width of the machine within 48 inches without the need of special, narrow skis.
The track suspension design allows for a wide range of adjustment for individual riding needs and conditions. The shock on the front arm has a threaded preload adjustment collar and the rear arm torsion springs perch on adjustment cams with four settings. Some XTRA-12 models utilize the Indy Select shock on the front arm of the suspension which incorporates an adjustable compression damping valve. Combined with adjustable limiter straps, the suspension can be custom tuned for an incredibly comfortable ride.
Narrower slide rails, which allow more snow to the rails for lubrication, and two additional idler wheels have been added over the 1995 design to reduce slide rail wear and friction. The long movement system does pull a couple miles per hour off the top-end, however, but it seems a small price for the comfort added by the system.
Changes in setup of the suspension result in very noticeable changes in how the machine handles and rides. One should get a basic understanding of the adjustments of the suspension from the dealer, and then spend an afternoon getting to know how you want your machine to perform. You won’t be disappointed!
The motion ratio of a suspension system is determined by dividing the travel of the shock absorber at each suspension arm by the vertical travel of the slide rail. With each inch of displacement of the slide rail, the travel of the shock absorber is measured and the calculation is made. If the ratio increases with more travel, the design is considered a rising rate system. If the ratio decreases, the system is considered a falling rate type. The Polaris design has about a 17 percent falling rate at both arms.
Twenty-one Polaris models feature the new, XTRA-10 rear suspension system. The design offers 8.2 inches of vertical travel and their Front Rear Scissor Stop (FRSS) which controls the bump attitude of the rear of the suspension. The FRSS consists of two position adjustable bump stops located fore and aft of the drop link from the rear arm at both slide rails. Providing more space between the stop and the drop link allows the suspension to transfer more weight during acceleration, a setup likely to be used by those fortunate enough to ride in deep powder snow. Shortening the distance between the drop link and the stop “couples” the front and rear arms more quickly. This means that as the front arm begins to compress from the force of a bump, the rear arm will start to move with it more quickly, reducing the impact of the bump on the rear of the suspension.
The XTRA-10 suspension is lowered in the chassis on the RMK models allowing better deep snow capability. All models fitted with the XTRA10 suspension have a 41-inch ski stance. The rear shock on most XTRA-10 equipped models is Polaris’ Indy select which features adjustable compression damping. The Indy Ultra, 600 XCR, 600 XCR SP and Storm use a Fox gas shock at the rear.
A longer movement front suspension, also dubbed the XTRA-10, offers 8.4 inches of vertical travel and is fitted on the SKS and RMK models.
The XTRA-10 suspension is noticeably harsher riding than the XTRA-12 and, depending upon how much “sit in” you dial in on the XTRA-12, no better handling. There is, supposedly, less top speed loss with the XTRA-10, but that was hard for us to confirm at the Rode Reports where pounding through moguls and sloshing through wet snow was the order of the day.
Ski-Doo Offers Up Suspension Smorgasbord
Ski-Doo re-entered the long-travel game with its 1995 SC-10 suspension mounted on the Formula SL, Touring LE and SLE and two Skandic models. For 1996, 20 Ski-Doo models ride on one of five versions of its long-travel, SC-10 design. The original SC-10 design by Bombardier was a falling rate design, aimed at comfort not competition. The system provides 9.6 inches of vertical travel at the slide rail. Three falling rate designs of the SC- 10 are found on several Sport, Touring and Mountain models from Ski-Doo for 1996.
The news for ‘96 is the use of two new, rising rate versions of the SC-10. A high-performance version, found on the Formula Z and Formula SS, offers 9.6 inches of vertical travel and incorporates geometry that produces a rising rate at the shock absorber. Both shocks on the track suspension are gas cell type shocks. Ski suspension travel was also upped on the high-performance SC-10 equipped models. Ski travel is at 8 inches, up from Ski-Doo’s standard 6.5 inches of travel with the DSA front end. Ski stance was pushed out to 42 inches for increased stability on the higher riding machine.
The ride quality on the high-performance version of the SC-10 is sensational, but the higher center of gravity is definitely felt when cornering, even with the additional ski stance. The rising rate design helps the SC-10 handle rear axle landings and those high speed sinkers that want to rip your ears off.
The cross-country version of the SC- 10 is mounted on the MX Z 583 and 440. Like the high-performance version, this one is a rising rate design, one aimed at competition. Both MX Zs utilize HPG shocks with internal floating pistons in all locations on the sled. The 440’s shocks are aluminum bodied, rebuild-able versions, allowing the competitor to do some custom calibrating.
The ski suspension for the MX Zs has 7 inches of vertical travel and the springing on the sleds is set up to allow more “sit in” to keep the center of gravity lower. The additional suspension travel is used as rebound travel, keeping the skis and the track in contact with the snow on those fade-away lumps. Ski stance is at 41 inches.
The handling difference between the MX Z and the Formula SS and Z is immediately noticeable. There’s no way a Formula Z is going to snake through the turns like an MX Z. On the other hand, the ride quality of the MX Z is noticeably harsher than that of the Formula Z and SS. Ski-Doo has done an intriguing job of setting the sleds up for their perceived applications.
Yamaha Sets The Standard
Yamaha enters the long-travel wars with its Vmax 500 XT and 600 XT, calling the rear suspension design “Pro-Action Plus.” Vertical travel of the slide rails of the all new design is 10 inches and compression at the front shock occurs at a falling rate while at the rear arm, the rate rises.
Yamaha’s new suspension design is very simple and has very low unsprung weight. The single rear shock operates in an almost horizontal position and does not attach directly to the rails. Both shocks are aluminum bodied rebuild-ables with nitrogen charged internal floating pistons. The front and rear shocks are by Kayaba and both have threaded bodies and spring adjuster collars.
Yamaha uses what they refer to as weight transfer control rods to “link” or “couple” the front and rear arms. Like the Polaris FRSS blocks, the control rods limit the amount of displacement of the front arm before the rear arm is forced to move up with it to avoid the oncoming bump. Plastic shims are used to adjust the amount of weight transfer before the front and rear arms “couple.”
Helping Yamaha’s new long-travel suspension to react to even the smallest bump are six sealed needle bearings, 12 high-density, greasable bushings, six high-density bushings and four greasable plain bearings. Every load point in the suspension rides on a bearing or bushing of some design which allows the suspension to react quickly with virtually no bind. This suspension is very supple yet handles the rough stuff incredibly well.
The front TSS suspension is unchanged on the Vmax 500 XT. Ski stance is at 40 inches and vertical travel is 7.2 inches. The Vmax 600 XT incorporates a spring preload adjustment collar for the TSS springs at the top of the strut. The rear heat exchanger on both XT models has been reshaped and mounts through the back of the tunnel to provide adequate clearance for the Pro-Action Plus suspension system.
Part of any suspension system on a snowmobile is the seat. Yamaha has always had the best seat foam in the industry and all the single seat Vmax models, including the XTs, will get 1.5 inches more of it for 1996. The seat has also been reshaped to allow more maneuverability and the added height provides more legroom.
Still On The Drawing Board
Arctic Cat has yet to release a long-travel rear suspension design. They did introduce their Extended Travel Tunnel (ETI’) design on the ZR 440 last season but have not increased the vertical travel of their FasTrack slide rail over the 6.2 inches of vertical movement found on most of their models. The ETI’ design allows the rear axle to travel through more displacement in the event of a tail landing, but it does little to improve the ride on a mogul infested trail.
Conclusions On The 1996s
The conditions at West Yellowstone for the 1996 Rode Reports were perfect for testing the long-travel suspensions. Warm weather and high rider populations left the trails in horrific condition. Freezing temperatures at night hardened up the nightmare moguls, providing us with an endless sea of tortuous bumps in the ungroomed areas.
The award for the all-around best ride and handling quality of the long-travel sleds has to go to Yamaha and their Pro-Action Plus design. At high and low speeds, the Yamaha design clearly outperformed the others in comfort of ride and handling in the rough. The TSS front suspension seemed to work even better with the Pro-Action Plus rear than on their standard models. Yamaha claims the new suspension has no effect on top speed, a fact we could neither confirm nor deny at the Rode Reports.
The one area of performance that did suffer with the Yamaha design was in weight transfer. The machine would spin fiercely off the line as it begged for more weight to be put on the track during acceleration. Shims could have been removed from the weight transfer control rods but the ride would have suffered somewhat, and with conditions as they were, we preferred the comfort of the ride over a drag race-winning holeshot.
The other conclusion we came to while riding the long-travel sleds was that the boys at Arctco had better have something up their sleeve, for the FasTrack, even with the Err, won’t run with the competition in the rough! SG