What is the Effect of Tire Size on ATV Performance?

Posted on April 5, 2018 by Weekend Warrior.

Text: Kyle Bradshaw

ATV-TIREv2When it comes to trucks, jeeps, ATV’s and UTV’s, oftentimes the first modification people make is larger tires. But why is this change made? For many it is just for the look. And for others, it is for increased performance in ground clearance and traction.

Aesthetically, “Bigger is Better” when it comes to ATV / UTV tires, but how big is too big? At what point do larger tires or wheels begin to negatively affect your vehicles handling, potentially putting you into a mechanically unstable or even dangerous situation?  Stay tuned, as we discuss this topic in depth.

IMG_0315Bigger tires can assuredly help you gain ground clearance and traction in sand, deep mud, snow or uneven terrain. As a general rule, most vehicles can safely handle an increase in tire size one or even two sizes larger than stock. From the factory our vehicles have been engineered to perform and behave a certain way with a specific size of wheel and tire combination. A good rule of thumb for an acceptable increase in tire size is 1 size larger for vehicles 500cc or less and up to two sizes larger for vehicles between 500cc and 1000+cc.

Increasing the size of your ATV tires will undoubtedly give your vehicle a much more aggressive look while increasing ground clearance and traction. However, there are some negative effects, which will most likely present themselves if not professionally addressed with quality aftermarket parts and accessories. Some of the potential issues are as follows:

  • Loss of Low End Grunt
  • Increased Clutch Wear
  • Tire Rub on Body Panels / Suspension Components
  • Increased Drive Belt Wear
  • Premature Drive Line Failure – Due to Increased Angles
  • Premature Axle Failure
  • Premature Wheel Bearing Failure
  • Increased Roll-Over Rate

Now that we understand the potential side effects, let us dig into the solutions to these problems so that we can safely and successfully run those big meaty and aggressive tires.

The taller or the larger the tire that you install on your ATV / UTV, the higher the gear ratio will become. Larger tires will also be heavier and will have a larger rotating mass, which will rob low-end torque and power. Your engine will strain harder to get the wheels rolling and once at speed, you will be fine until you encounter an obstacle such as deep sand or mud, where the ability to spin the tires quickly in mud will be diminished. The solution to these issues will be a gear reduction kit or the installation of a clutch kit. These solutions are different… so choose the kit, which will best serve your needs. Essentially…
- Gear Reduction Kits will allow the wheels to spin faster.
- Clutch Kits will allow the engine to rev higher before engaging.

NOTE: Please keep in mind that both of the above fixes will cause a loss in overall top speed.

EPI - Clutch Kit Example

EPI is a fantastic company when it comes to helping riders get bigger tires onto their vehicles. In a conversation with EPI we were told, “Our approach here at EPI Performance is to get our hands on every ATV, UTV and Snowmobile out there. We develop our Clutch Kits by putting on the miles in sand, mud, snow and trails the way you do. It doesn't become an EPI Clutch Kit until we're satisfied with how it performs in the REAL-WORLD of riding.”

But how much will a custom clutch kit such as this cost? It’s actually pretty inexpensive. For example, at right around $300, EPI makes a clutch kit for almost every ATV allowing them to run 27” or 28” tires, take a look:

This EPI Clutch kit will allow your ATV to enjoy these benefits:

  • 398-0202Designed for 27-28" Tires
  • 0-3000' elevation
  • Our best all around use kit
  • Great for trail riding, occasional mud and sand riding, plowing and hauling
  • Makes up for the power loss and slow response of adding oversized tires
  • Better low end and midrange acceleration
  • Quicker backshift which results in crisp throttle response
  • Reduces belt slip and clutch heat

Heavy Duty or Severe Duty Belts

The addition of larger tires and a hopped up clutch kit will make quick work of the OEM or stock CVT drive belt. A Heavy Duty belt, also known as a Sever Duty Belt will most likely be the next upgrade on your list. Here are the benefits of a Severe Duty Belt:

  • Made of highest quality materials
  • Deep double cog style reduces clutch heat
  • Designed for sever duty applications
  • Can handle larger tire sand aftermarket clutch kits

Drivetrain and Suspension Upgrades

The stock drivetrain and suspension components of most ATV / UTV’s are not built to withstand the extra stress that significantly oversized tires bring to the table. These added stresses will accelerate the wear and tear on these components and can lead to premature failure, failure which will most likely happen much faster than with OEM sized tires. To avoid a catastrophic failure, you may want to consider installing the following heavy duty components:

  • Axles
  • CV Joints
  • U-Joints
  • A-Arm Busing and Repair Kits
  • Tie Rod Ends
  • Shocks
  • Wheel Bearings

341-1197Lift Kits & Wheel Spacers
For most ATV / UTV drivers, the main functional reason for installing larger tires is to lift it higher for more ground clearance. With the chassis raised further from the ground, the center of gravity is also raised.  A raised center of gravity can make any ATV / UTV unstable then it was stock while going through corners or traversing sideways on hillsides. Installing a lift kit with a wider stance or a set of wheel spacers can help make your vehicle wider, placing the wheel further from the shocks, struts and exhaust for proper clearance as well as increasing vehicle stability. Lift kits and wheels spacers can also help correct the reduced turning radius caused by larger tires reducing the increased steering resistance caused by the initial tire size increase.

When No Mods Are the Best Mods

Larger than stock tires are badass, but if all you are looking for is a slight increase in ground clearance or appearance you can go up “just a bit” to achieve that look without the need to make any of the aforementioned modifications. The measuring tape will tell all, but generally speaking, ATV / UTV manufacturers typically leave enough space to go up at least one size and maybe two sizes in tires without the risk of rubbing on plastics, shocks or exhausts.

Have Fun & Ride / Drive Safe

IMG_1133We hope that this article has been beneficial in helping to understand what is needed if you want to Super Size your ATV or UTV.  If you keep it mild, fewer modifications will need to be made and you will be able to retain your OEM level of performance. If wanting to go larger than one to two tire sizes, additional modifications will be necessary to protect your vehicle from breakage and to keep your vehicle running in tip-top form.  If you have any questions, please reach out to our Customer Care team via email or call us at 909-889-2761.  Thank you for your support. Until we see you next, take care and ride / drive safe.

Comments
  • Ken Sample
    I have a 500 Polaris ATP w/27” tires on it and it’s tearing up drive belts quickly.What should i do?Clutch kit?
    • Eric Ellis
      Hi Ken, thanks for checking out our blog. Did you have belt issues before you installed the 27" tires? The larger/heavier tires would make the machine work harder as whole and could cause belt problems. A clutch kit would help in reducing belt slippage. EPI offers a variety of clutch kits.
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