longer is better

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Every time I climb on a longer tracked crossover sled I'm surprised by how agile it can be, even on tight trails.

It really shouldn't surprise me though, I understand the advantage of a longer chassis. Yet when you've spent most of your life racing motorcycles, snowmobiles and cars, you tend to look for the lightest and shortest combination to make sure you're quick in the corners.

You can, however, end up with a race machine that's a lot quicker and more agile than YOU are - even though your ego argues that you're as quick as anyone out there.

Length helps in corners

I once built a racecar with a short wheelbase to get an advantage in the corners. Turns out the car's steering was so quick that I had to make several corrections in each corner. The resulting erratic line through the corners slowed me down and made the car squirrelly to drive. Maybe if I had been Mario Andretti, or had quicker reflexes, I could have handled it. But I faced reality and extended the wheelbase.

The change was amazing. The car became smooth and predictable, a big change from the scary, twitchy handling I was used to with the shorter wheelbase. My corner speeds actually increased and I cut my lap times as I gained confidence that the car wouldn't make any sudden sideways moves in the turns.

Motocross racing provides another example. When Yamaha introduced its Mono Shock suspension in the late 1970s, most everyone was convinced the layout of the suspension was the secret to the improved handling. But I came across a story in a British bike magazine where the author claimed that the reduced tendency of the bike to pitch back and forth over moguls came from the bike's swing-arm that was much longer than other race bikes.

So, we lengthened the swing-arms on our race bikes and found that length to be a big advantage in the moguls. The bikes also steered better in the corners because the driver could now put more weight on the front wheel. All this was in response to problems that started showing up as suspension travel got longer on motocross bikes.

Sound familiar? This is the stage where snowmobile evolution is now.

Length decreases pitch
Snocross racing has led to great strides in suspension design, but as travel increases more pitching is introduced to the chassis. So how do you fix the problem?

Better shock dampening is one way. It controls pitch. Moving the driver forward so he sits in the center of the pitch is another solution. But sooner or later you come to a point where more travel or more dampening doesn't do the job.

Not surprisingly, lengthening the sled slows the pitching frequency and also calms erratic sideways behavior. Bob Eastman used this solution when Polaris came out with the first IFS oval race sled. But the greatly increased grip of the ski carbide made the first prototype so hard to drive that Polaris almost abandoned the concept.

Eastman solved the side-to-side pitch problem by moving the skis forward and lengthening the sleds. This twitchiness wasn't caused by the same pitching motion you get over moguls, but rather a harsh sideways input from the ski's carbide, much like the "hunting" often experienced with harder loaded modern skis.

With a continuous move toward more suspension travel on our snowmobiles, the trend toward more up and down motion has developed. This is especially true on a short-wheelbase sled, wheelbase being the length from the skis to the middle of the track. Lengthening the track moves the rider more to the center of the pitch and gives him or her more control, while smoothing out ride.

That's one reason why longer track sleds are becoming more popular. The "crossover" models use lengths from 128 inches to 144 inches, with the 136-inch track currently being the most popular.

Why it works so well
A sled with a longer track rides smoother over large moguls with a lot less chassis pitch, and it almost ignores smaller stutters or ripples that otherwise make the rear-end nervous.

While we may fancy ourselves a Blair Morgan over the moguls, it's hard on the body to get pitched up, down and sideways by a short track. If you've ever seen Blair in action, his secret to taking big moguls is very careful timing and a good choice of lines, something he probably picked up while motocross racing.

On snowmobile trips where I need to charge hard down the trails, I try to land myself on a longer track "crossover" machine because in the bumps it's much easier on the body than a shorter tracked machine. Arctic Cat's Crossfire 700 was a nice example of the breed this past season.

My all-time favorite and probably the original crossover machine was the Polaris SKS with a 136-inch track. Aside from better flotation on the snow, which made it popular in the mountains, the machine handled surprisingly well on trails. At the time, the suspension travel was nowhere near as long as our newer sleds, but the longer track made it stable and predictable in the turns because the sled actually was reacting slower to the bumps. Likewise it made the sled ride smoother in the rough, with added traction.

The SKS was meant more as a mountain sled, but soon became popular in the Midwest because of its handling and ride.

Another nice surprise has been Yamaha's Rage. Its 136-inch Ripsaw track adds stability and delivers good traction. But the best feature is its ability to transfer weight off the front, making the machine feel lighter. The Rage is fun to slide around corners, you never feel that the rear end is going to come around and pass you. I also like the Pro Action CK suspensions. The combination gives a flatter ride in the rough and I feel better throwing this around on trails than the shorter Vector.

I also fell in love with the Ski-Doo 1000 X Renegade in the short time I rode it on twisty trails in our Utah test session last spring. It has the right combination of traction and handling for the big motor.

The Renegade feels surprisingly light because the power lifts the front on demand, but the rear-end is planted with a controllable drift in corners due to its longer track. It was great to be able to stay with lighter sleds in corners and blow them off at will on short straights.

A new favorite
A short studded 121-inch track has been the favorite on groomed Midwest trails for years now, but with increased suspension travel and more powerful engines, the 136-inch track in various lug sizes is fast gaining ground.

Longer has a lot of advantages - less pitching in large moguls, smoother ride in stutter bumps, more traction and a more controllable ride in corners. Cars, motorcycles and snowmobiles all have to obey the same physical laws, and, it's safe to say, lessons learned in one area usually apply in the others.

After all, we shouldn't be surprised that what worked on cars and motorcycles, also works on snowmobiles. In fact, it's very reassuring.