Polaris Changes How Wheel Travel is Viewed?
A couple of years ago, Polaris introduced a new way of expressing suspension travel that seemingly turned the tables on one of their biggest competitors.
By injecting the term, "Usable," in front of the term, "Travel," Polaris sought to re-educate potential buyers and introduce them to a different way of looking at suspension travel numbers.
This new metric made Polaris' numbers appear ever so slightly better than their competition's, even though their advertised wheel travel was less.
Was it simply a marketing ploy or a better way of looking at suspension travel?
How is Wheel Travel Calculated?
In a nutshell, suspension or wheel travel is normally considered to be the maximum range of motion a vehicle's suspension has. This is most often measured in inches in the U.S.
In order to measure wheel travel the suspension is compressed to the point that either the spring(s) or shock(s) can no longer be compressed any further. The initial measurement is then taken at the center of the hub at the axle.
The next measurement is again taken at the center of the hub once the suspension is allowed to fully extend.
The wheel travel is the measured distance between the two points.
This can be as little as 5" on a Mini Cooper to 36" on an Unlimited Class off-road truck.
So, Why Should We Look at Wheel Travel in a Different Way?
Wheel travel, as calculated above only tells part of the story.
Let's consider a few facts.
If the bottom of the car slams the ground, frames can crack, bend and even break over time. Skid plates can be damaged or lost. And most concerning, the occupants can be injured, especially in their lower back.
At the other end of the suspension cycle on a UTV, if the suspension is allowed to extend fully without consideration of the angle between the axle and the CV shaft, damage to the CV, axle, or other drive components can occur.
Don't sweat it if you are operating a UTV with an originally equipped suspension. Even though there are a few forum posts out there that imply one of the biggest UTV manufacturers has a unit with a suspension that will indeed bottom out on flat ground 2" to 3" before full compression.
I have not seen data that either supports or disputes this but I would be very surprised if it were true.
Please leave a comment below if you have data pertaining to this subject.
Now, if you decide to start changing things such as replacing the stock suspension arms with an aftermarket long travel kit, you might want to know all of the pros and cons of doing so.
Long Travel Kits for UTVs, once installed, are going to change some things, but I believe the top names in the business have done their homework.
However, there is one thing you may want to know. That is, if you are installing a long travel kit you may want to consider changing to a slightly taller tire in order to take advantage of what the LT kit has to offer.
For the reason that, with the addition of an LT kit, half of the small amount of wheel travel gained will be at the top of the suspension cycle while the other half is at the bottom due to simple physics.
This gained wheel travel at the top of the cycle is going to put your skid plate closer to the ground at full suspension compression. This could be harmful due to potentially allowing the bottom of the car to hit the ground when it may not have before, with the stock A-Arms.
For instance, when installing a long travel kit on my Yamaha YXZ I also increased the tire size from the stock 27" tires to 32's. When I removed the springs from the rear shocks and allowed the shock bodies to bottom out, the measured ground clearance was 1.25". You don't need to be a rocket scientist to realize what the ground clearance would have been with the stock 27" tires.
Taller tires will help you regain some of that ground clearance lost at full compression. But, as you might suspect the taller tires will cause the UTV to have a little less power at take off but will increase top speed. Bigger tires also create more stress on just about every other suspension piece and drive component.
Therein lies the old race car truth that for every change made, something else is compromised.
With all of this said, you should now have a better understanding of how important just a few of the issues are, that must be considered when designing a suspension system.
So, How did Polaris attempt to Change the Game?
Polaris' new key description is, "Usable Travel."
This is how they word and measure it:
"Usable Travel is measured, with the vehicle in full droop, from the bottom of the tire to the bottom of the skid plate."
Here are a couple of definitions for newcomers:
- Full Compression = Bump
- Full Extension = Droop
The problem is, without all manufacturers providing us with the same numbers, this doesn't help us much when trying to make a comparison.
- How tall are the tires? This makes a difference with their methodology.
- How much clearance is there between the bottom of the car and the ground when the suspension is fully compressed?
Bullet point number 2 brings up another question:
- What is the optimum amount of ground clearance that a UTV should have at full bump? (Suspension Fully Compressed)
What is the optimum amount of ground clearance that a UTV should have at full bump?
There is no right answer to this question for all UTV applications. Someone who rides deep rutted trails or desert races may desire to have more clearance at full bump. Someone who races short courses will definitely want to have the center of gravity of the machine set low as possible leaving very little ground clearance. A weekend warrior who may ride in many different areas with dissimilar terrain may want their ground clearance somewhere in between.
What if the rear skid plate of your UTV hits the ground before the suspension reaches full bump, what good is the left over suspension travel?
In conclusion, Polaris may indeed have found a way to compare themselves to the competition in a meaningful and helpful way. For all that, without more data from Polaris and their competition to make an apples to apples comparison, we simply don't know.
One thing is obvious, Wheel Travel and Usable Travel as described by Polaris, are two totally different beasts and one should not be compared to the other.