Tricked Toys Wheel, Offset Axle & Track Size Guide
Tricked toys offset axles are generally designed to be run with the offset facing towards the front of the sled. However, in some applications the axle can be run with the offset facing the back of the sled. It can become confusing when you are trying to change the size of your rear wheels, as sometimes you may require a longer track, or special offset axle for certain applications. In this guide we will teach you how to make these decisions so the products you buy are compatible with the ideas you have!
Forward Facing Offset
For application using a forward-facing offset there is some information which must be considered. Forward facing offsets allow for a 1” – 2” increase in wheel Diameter. Wheels should be mounted in “Hole 2” for a 1” increase in wheel diameter and “Hole 3” for a 2” increase in wheel diameter. This means that you can go from a 7.1” wheel to an 8” or 9” wheel, or from an 8” wheel to a 9” or 10” wheel. (NOTE: 11” wheels are only viable in specific and custom applications). “Hole 1” is where the offset axle mounts to the windows of the rails. With a 136” track or longer a 2” offset (wheel diameter increase of 2”) is the maximum amount achievable without any further modifications.
Figure 1.
Backward Facing Offset
Backward facing offset axles are commonly used for drag racing applications. This generally means using a larger rear wheel as well as a longer track. This reduces the friction coefficient of the wheel which conserves horsepower, which is lost in the transfer of energy from the drivetrain to the track. The longer track also improves the traction the track gets. Both scenarios together ultimately enhance the performance of the snowmobile for drag racing applications.
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The problem arises when trying to determine how much extra track length the wheel utilizes, as well as how much track length the backward facing offset utilizes. The next part of this guide will explain how to determine the total track length that is used by these two different situations.
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Firstly, we must determine what the half circumference of the wheel is. The half circumference of the wheel is the surface of the wheel which is engaged with the track which is generally half. The equations and results are displayed below for our oversized wheels.
The next step in this process is to subtract the wheel size you’re currently using from the wheel size which you desire to use. The equation is shown Below.
As an example, if we want to go from an 8” wheel to a 10” wheel you must subtract 12.56 from 15.70 the result of this subtraction is 3.14 inches. This means that your track must be an additional 3 inches longer. However, we must then consider how much track length is taken by the backward facing offset.
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The distance between “Hole 3” and “Hole 1” from Figure 1 is how much the rail is being extended by (considering where the axle is in the adjustable window of the rail). That distance is 1.65” this number must be multiplied by 2 to become 3.3” the reason we multiply it by 2 is because the increase in relative rail length is equal to 2 times that in track length (because the track of the snowmobile runs in a loop around the rail meaning there is an increase in length on the top and bottom).
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Considering 3.3” and 3.14” from our earlier example; we add those values together to get the total amount the track needs to be increased by, which is 6.44” roughly 6.5”. At Tricked Toys we find that most people looking to use their sled in drag racing applications have a 137” track and go to a 144” track while also increasing their wheels from 8” to 10”, this is because the additional 7” of track length is taken up by the backward offset and increase in wheel size. It is also important to acknowledge that the window in the rail which the axle is mounted to has roughly 1.25” of adjustability in either direction ([2.5” Rail Window]/2 = 1.25”). This means that in our example if the axle was originally mounted in the centre of the window, we would have 6.5” ± 1.25” of required track length increase, which is 5.25” ~ 7.75”. this means that increasing your track length from 137” to 144” (7” increase) is well within the acceptable range.