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Tracking Your Sled's Performance

Published online: Jan 04, 2005 Feature Robbie Holman
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It has been my experience that when someone gets a new sled, the first things they buy are a pipe, reeds and a few lightweight parts. More horsepower means more torque at the drive shaft. Sooner or later the track starts to ratchet. This is true for mountain sleds as well as short track sleds in the Midwest and East. Mountain sleds use longer tracks to get traction and short track sleds use studs. Either way the new owner tightens up his track to reduce ratcheting.
That is fine, but a tight track doesn't roll as easily as a loose track.
You can see this on your own sled at home. Put it on a stand and take off the belt so you can rotate the track. Use a fisherman's scale and see how much force it takes to make the track move. Now loosen the track so that you can get your finger between the track and the hyfax. Measure how much force it takes to spin the track now. You should see quite a reduction. My sled with a 162-inch track with an 8-inch big wheel kit and a set of anti-ratchet drivers (combo drivers or extroverts) pulls at 10-12 lbs. Any drag over 10-12 lbs. is like having your brake on all the time. You could be-and probably are-using 3-5 hp just to overcome that extra drag at 40 to 50 miles an hour.
It's only logical that the less resistance is in the drive system, the greater track speed will be. Anti-ratchet drivers and big wheel kits help to lower that resistance. That means increased performance without affecting the reliability of your engine.
If you are replacing your present track, you will be able to increase your performance by buying a track with a 3-inch pitch. A track with a 3-inch pitch will weigh less than a 2.52-inch pitch track of equal length. An old rule of thumb is that for every pound of rotating mass you can remove, it is like taking 7 pounds off your sled. Putting a 5-6 pound lighter track on your sled will increase track speed.
When you are selecting what size of 3-inch pitch anti-ratchet drivers, you should consider several things. An 8-tooth 3-inch driver is approximately one-half inch bigger than the 9-tooth 2.52-inch driver you probably have in your stock sled. A 7-tooth 3-inch driver is a 1/2-inch smaller. A bigger driver might seem the logical choice. Not necessarily-tracks act like conveyor belts, carrying snow and air to the front of the tunnel and around the drive axle. If there isn't anywhere for this air and snow to go, it piles up in the front of the tunnel and slows the track down. Unless you have a lot of room up front, it will be better for you to use the smaller driver.
A third item you should think about is chaincase gearing. Mountain sleds as they come from the factory are geared too high for mountain riding. There is a simple way to see how efficient your gearing is. Mark the inside sheave of your primary clutch with a permanent marker and go riding. After you have gone on a couple of trips, look at the mark. If the mark hasn't been wiped off of the sheave, you can gear down and not affect the top speed of your sled.
I have talked with people who are afraid to gear down, because it will affect their top speed. If you aren't wiping all of the mark off the clutch, then either you don't have the horsepower to go as fast as you are geared or the top speed of your sled doesn't fit your riding style. Lower gears increase drive belt life because the normal operating range is moved out further from the center on the primary clutch. More of the belt is in contact with the clutch sheaves and is less prone to slip and reduces belt temperature. You will also gain more throttle control at the lower speeds. Your engagement will be smoother and you will be able to get started in really soft snow without digging a hole.

(EDITOR'S NOTE: Holman is the owner of Avid Products. For more information, contact 866-666-2843 or www.avid-products.com.)

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