“Hello sir, how can I help you today?” the salesman behind the counter asks.
“Well, I just purchased this new side-by-side and now I want to put some new tires on it—you know, like those big ones right there,” the customer says. “They look cool.”
The salesman looks at the tires and responds, “Those are the Super Mud Destroyers. They’re a 30-inch tire which can be too large for some UTVs and are designed for mud only. What type of riding will you be doing in your new side-by-side, Sir?”
The customer explains, “Oh you know, a little bit of everything. Mostly camping and stuff, but it doesn’t matter. I like those Destroyers or whatever you called them. I’ll take ‘em.”
Two weeks later the customer comes back to the dealer and asks for the same salesman.
“Hello sir, it’s good to see you again,” the salesman says. “How do you like your new side-by-side?”
“Well, my wife and I have now put more than 500 miles on our side-by-side but I’m a bit disappointed actually. It doesn’t go very fast and the tires are really noisy. Plus it doesn’t seem to have much power and my tires seem to be half-way worn out already. Any ideas why?”
The salesman replies, “Those tires you chose are much bigger than stock and in most cases require a different clutch setup to compensate for the added gear ratio and heavier weight which can hurt acceleration and top speed. Not only that, but because they are an aggressive tread, they make more tire noise and tend to wear quicker than other tires if driven on pavement.
“They are a great tire for mud where they will outperform the stock tires, but they can be a disadvantage everywhere else. They are a purpose-built tire.”
This scene is an example of a UTV owner installing the wrong tire on his UTV for the type of conditions he usually drives it in.
UTV tires are just like tires for any other wheeled vehicles: there are many different tire options, each with a different intended use. Variables that need to be considered when choosing a tire include vehicle speed, weight, terrain type, tire wear, side wall strength, wheel type, noise and cost.
However, many customers choose a tire based on looks alone. It’s important to consider how the UTV and tires will be used when choosing which one to install on your UTV.
Tire Size
As we have all heard before, size matters. And it has never been truer than it is with UTV tires. Tire size can be a huge factor in UTV performance. Changing tire size can affect things like ground clearance, top speed, corner speed, center of gravity and traction.
For many people, changing to a different size tire will help their UTV perform better for the conditions they plan on driving in. But if you’re going to change your tire size you first need to know what size you have.
All tires have numbers molded into them from the factory that indicate the size. For example, let’s say you look at your UTV tire and it has the letters/numbers 25x8R-12. The 25 represents the height of the tire in inches. The 8 represents the width of the tire in inches and the 12 represents the diameter of the wheel. Now that you know what tire size you have, you can decide what tire size you want to change to.
For people who spend most of their time off road, installing a taller tire will offer increased ground clearance. It gives them the ability to crawl over stumps, cross creeks and maneuver over rock ledges. The taller the tire, the larger the obstacle they can drive over.
Tire size also affects gear ratio. A taller tire will result in a higher gear ratio while a smaller tire will result in a lower gear ratio. This can be both good and bad. A taller tire offers the potential for a higher top speed, but only if the tire has less weight, less rolling resistance and the clutches have been properly calibrated for the larger tire (more on this later).
On the flip side, a tall tire can also be a disadvantage. Get the tire too big and it will rub on body parts, fenders and wheel wells as well as raise the vehicle’s center of gravity. Additionally, taller tires usually weigh more than a comparable smaller tire, requiring more power to turn them. The heavier the tire or more aggressive the tread, the more power they rob. This hurts acceleration and top speed.
Smaller tires can be an advantage in some cases as well. Closed course moto and grand prix type racers prefer a wider, smaller diameter, low ply tire to give the vehicle a lower center of gravity for better cornering and stability. Major ground clearance is not needed for most track type racing so the lower the vehicle rides the better it will handle.
Another advantage of smaller tires is that they typically weigh less than their larger relatives. Less rotating weight requires less horsepower, resulting in better acceleration and speed. And as stated before, reducing tire size will lower the final gear ratio. This will help acceleration and power but potentially reduce top speed and sometimes require the clutches to be re-calibrated for the smaller size.
Tire Weight
The rule is pretty simple: the heavier something is, the more force required to move it. This is especially true when you’re talking about something that rotates at high speeds. If acceleration and speed are important to you then weight should be as well.
As a general rule, the larger the tire, the more it will weigh, but this is not always the case. There are several factors that affect how heavy a tire is. For example, carcass design, tire thickness or ply, tread pattern and of course overall size all contribute to weight. Occasionally there will be a tire that, though larger in size, will weigh less than a smaller tire because of differences in carcass design, tread and ply.
More often than not, the thickness of the sidewall or “ply” can be a clue as to how heavy the tire will be when comparing tires without a scale. A 2-ply tire will have a tendency to be much lighter than the same size tire that has 6 or 8 plies, but typically the more plies a tire has, the stronger and more durable the tire will be.
Tread Design
Tread pattern is what can really fool a buyer. It’s easy to get sucked into what looks cool and aggressive or, on the flip side, what looks like the perfect tire for a Saturday back road trip. But as our little scenario above displayed, it has more to do with where and how you ride than anything. So what type of tread is the best for each condition? Let’s break it down into two categories: tall, skinny tread and short, wider tread.
Tall, skinny tread with large gaps between each tread are used for softer soils and mud where penetration and cleanout is extremely important. These tread designs generally wear quicker when used on hard surfaces and typically have more road noise. They are often less stable due to the higher thread profile and can perform poorly at high speeds.
Shorter, wider tread with narrow gaps between each tread are often used for harder surfaces such as rock, hard dirt and gravel where cleanout is not important but contact surface area is. These tread designs typically offer longer tread life with less road noise. They are better for high speeds, but offer less traction in soft soil conditions and mud.
Air Pressure/Sidewall Flex
Air pressure is a huge factor in tire performance. Some types of terrain require low tire pressure for maximum traction and performance while others require the opposite.
A tire will have better grip with lower tire pressure and more sidewall flex. This is the case when driving in rough terrain like what would be encountered when traveling in the backcountry over logs, rocks, stumps and ruts. At slow speeds, tires can be run as low as four pounds in these conditions.
Keep in mind lower pressures increase the risk of a flat caused by sidewall puncture, tear or bead breakage around rocks or trees. Rim damage can also occur from hard impacts when running a lower tire pressure so it is a good idea to use a heavier ply tire and keep speeds to a minimum.
Rock crawling or riding on sand can utilize pressures as low as three or four pounds if the speeds are kept low.
A bead lock rim can be a life saver in these conditions, allowing you to run very low air pressure without getting a flat, sometimes as low as one or two pounds. These types of pressure would not be safe to run at high speeds, as the stability and handling of the vehicle would be very poor as well as the risk for a flat or rim damage would be extremely high.
Again, to reduce sidewall punctures, a heavier ply tire is recommended.
Higher tire pressure is more suited for conditions where stability and speed are more critical. Now we’re not talking the kind of pressure you would see in a car or a truck. Rather, 8-14 pounds is usually recommended for most UTV tires to be stable and safe at most speeds (consult tire and UTV manufacturers’ specifications for final air pressure settings). In fact, a tire with more air will generally go faster for a couple reasons. First, the rounder (or narrower in this instance) the tread pattern portion of the tire is, the less rolling resistance it has, and second, some tires will get larger down the center line with higher air pressure, effectively giving the vehicle a higher gear ratio.
Rolling Resistance
We kind of touched on this already but rolling resistance is more of a factor in UTV performance than most people realize, especially when talking about acceleration and top speed.
Features of the tire that affect rolling resistance are things like carcass design, manufacturing methods, tread design, tire weight, height and width. The problem is it’s tough to know by looking at a tire if manufacturing or carcass design are good until you actually test the tire.
In general, a narrower tire will roll easier than a wider tire because of friction and drag.
Remember the old days when all the race cars had really tall narrow bicycle type tires--they had very little traction but had extremely low rolling resistance. The same theory applies to a UTV tire. If you want to increase top speed, a narrower, lightweight tire will help.
Clutch Calibration Clutch calibration is one of the most misunderstood and overlooked categories when it comes to tires. Because most UTVs use a centrifugal transmission system, performance can be affected by changes in load. Changing tires almost always changes the load placed on the clutches and motor, which will effect acceleration, response and top speed.
The good thing is that performance can be returned and, in most cases, increased by recalibrating the clutches to work specifically with your new tire choice.
Aftermarket companies manufacture clutch kits that have been specifically designed to offset the performance lost from changing to a different type of tire. You would need to contact the manufacturer of the clutch kit in order to find out more information and applications.
As you can see, there are many variables to be considered when determining which tire is correct for your driving style and terrain. But now that you know what variables to consider, you should have a much better chance of choosing the correct tire for you and preventing the reenactment of the story we saw before.
