Gear Reduction: A Quick Guide on How Super ATV Porgal Gear Lifts Work

Feb 14th 2020

We're sure at some point, you have heard UTV enthusiasts talk about gear reduction. Many riders like to get in the seat of their ATV/UTV and punch on the gas without giving much thought to the hamsters in the drivetrain components that are turning the wheels. You shake your head and act like you understand, but really, it all seems a little fuzzy. After all, it involves math... and math sucks.

This guide is to answer some common questions about this mystical force that lets your cousin ride like a pro, while you are getting winched out of the holler. We are going to help you understand why gear reduction is important, why you might need it, and how you can get it. Spend some time reading now, and you will be talking ratios and torque with the best of them.

Why should You care about Gear Ratio?

You should care about gear reduction mostly because it helps to provide more torque and power to the ground.

Another word most claim to understand, but just in case you don't - we are going to explain it. Torque is the amount of power that your engine produces to turn your tires. Simply put, the more torque your Polaris, Can-Am, or the machine of your choice can produce, the faster you can accelerate or the easier your engine can turn your wheels.

May the Force Be With You [in lb/ft that is.]

This force is measured in pounds per foot (lb/ft). Think of this as how hard you need to crank a foot-long wrench. If you are tuning a lug-nut with 20 foot-pounds you are applying 20 lbs of force at the end of the wrench to turn the bolt. (If you really want to geek out, check out this cool article about different reduction types.) Your engine is turning your wheels just like a wrench turns a bolt, but with a lot more force. This is where the gears come in. They help to produce this force on your wheels that is generated by the engine.

What Do Gears Have to Do with Torque?

Depending on how your Side by Side is geared, torque can result in two things, speed and power. If your Side by Side has a higher gear ratio then it might take longer to get rolling, but once it does it will go fast. On the other hand, a machine of the same size/weight with a lower gear ratio will have lots of power to get rolling but might not reach as high of a speed. This may sound familiar from your high school physics class. Basically, this means that smaller gears can turn one revolution more quickly than larger gears. They don't produce as much force during those revolutions, but they can go faster. This is a very simplified example, your transmission has more than one gear, but you get what we are trying to say (we hope).

Animated model of working gear reduction This animation shows a working gear reducer. The smaller gear is turning at a faster rate than the larger gear.

What is the Difference Between a CVT and a Traditional Transmission?

Illustration of a working CVT style UTV transmission
A Continuosly Variable Transmission (pictured here) uses a pulley and belt to shift "gears"

We don't want to confuse you, but most UTVs don't have a transmission that is shifted like a traditional car transmission. Most manufacturers, including Polaris, Can-Am, and Yamaha (except for the YXZ model) have equipped their machines with CVT style transmissions. This stands for Continuously Variable Transmission. We won't go too deep into how these transmissions work. You can take a look at the video if you want to know more, but some would argue that these transmissions don't have a true "gear ratio."

Instead, they adjust continuously while accelerating. It's like having one magical gear that's variable across all driving situations. You feel the engine shifting from one gear to the next like in a normal car. All you'll notice is changes in engine speed, or RPM: higher for acceleration, lower for cruising. Even though the transmission operates differently – it does have gears, and based on their size (and ratio), they will help determine the amount of torque the engine is able to provide to your wheels.

Do I need more torque?

Do you need more torque? That is a good question. It really depends on how you ride, but more than likely the answer is, at some point, yes. A side by side that rolls off the showroom floor usually has a clutch and transmission set up for a balance of speed and power based on stock equipment. Your average ATV/UTV rider might find this completely adequate, but if you are all about hitting the trails and getting the blood pumping, you probably have already upgraded your machine. The list of upgrades that can potentially affect the performance of your ride is long, but we are going to focus one of the biggest culprits. Tire size.

How Does Tire Size Affect My Torque?

Nothing makes your new ride look bad-ass like some big o'l tires. They aren't' just for looks either. Bigger tires help you get better clearance on the trail and get better leverage on obstacles too. However, if you add bigger tires to a stock machine it comes at a price, you lose torque. Here is why. First, you are adding weight. An increase from a 25" stock tire on a Polaris Ranger XP to a 32" tire could add as much as 250 pounds or more to your machine. Also, that weight is being added to the very thing that the engine is trying to turn, your wheels. If you have a factory clutch setup, this makes it more difficult for your engine.

Big tires on a UTV can affect the torque
A Side by Side with increased tire size can experience a loss in power. Installing GDP Portal Gear Lifts can help.

Big Tire Challenges.

The second (and biggest) torque killer with larger tires is the distance around the tire, or the circumference. When most riders say bigger tires, they are talking about the height off the ground. This is how tires are sold. The size of a tire is the height of the tire from the ground, but taller also means it measures greater in the distance AROUND the tire. If we think about the tire as a gear it takes more force to roll a bigger tire 1 revolution because it needs to travel a farther distance.

An Easy Way to Determine the Gear Reduction You Need.

You can skip reading this next part and use this gear reduction calculator, or you can keep reading and learn something new. We suggest you keep reading.

If you marked two tires, one 25" and one 32," and rolled them both together for a total of one complete revolution -- or the distance it takes for that mark to travel from the ground all the way around and back again the 25" tire would travel about 78.5 inches while the 32" tire would roll about 100.5 inches. Trust us on this one- it's math...we know, math sucks. (If you want to know more about the math check out the article on determining gear ratios.) To roll that bigger tire the extra distance your engine is working harder because it needs to spin it more to make one revolution. In this example, if we figure the percent increase from 78.5 inches of travel to 100.5 inches we find that you are losing 28% of your torque. This translates into a loss of speed and power.

And now, my friends, we have come full circle. If you want to make up for that loss caused by your bigger tires you need more need a gear reduction! How much reduction do you need? The answer is enough to replace what you lost by increasing your tire size. If you go from a 25" tire to a 32" tire you would need a reduction of about 28%.

I'm Sold. How Do I Reduce My Gear Ratio?

The two best ways to reduce your gear ratio on your UTV or ATV is to install a transmission gear reduction kit or install a portal gear lift kit. You have to decide which is right for your budget and for your skill level in the garage.

Advantages of Transmission Reduction Kit.

Simply put, the biggest advantage is price. This will cost a lot less than a portal gear lift. You won’t spend more money, but you will spend more time. A lot of it. Most transmission kits on the market offer between 12%-25% gear reduction, and they require you to take apart your transmission and replace the factory gears. This can be tricky if you aren’t a weekend warrior with a wrench, and if you have a dealer do it, you probably won’t save any money.

If cracking open your transmission doesn't seem like a great idea to you, we recommend that you look at getting a set of portals. Here are some of the advantages:

Advantages of GDP Portal Gear Lift kit.

  1. Portals are easy to install.
  2. Unlike a transmission kit, there isn't a need to replace your factory gears. Instead, a portal gear lift is attached to the end of an axle at the wheel hub. The reduction and increased power come from the gears that are built into the box that operates at the wheel. This makes installation much less time consuming and accessible to all riders.

    Diagram of internal gear structure for portal gear lifts
    SuperATV's GDP Portal Gear Lifts (shown here) transfer engine power to the wheels via a gear recuder mechanism contained in the lift housing.

  3. The additional power is applied directly to the tire.
  4. Portals transfer the force of the engine more closely to the object being turned (the tire) so there is less stress on the drive shaft and the factory transmission.

  5. You retain factory steering geometry.
  6. You probably need more torque because you added bigger tires or a lift. Remember? That means you also probably put your axles to work at an angle that they aren't used to because they are now connected to your wheel hubs from a different height than factory. This can cause a lot of stress and wear. An advantage of gear down with a GDP Portal lift is that it relocates the axle centerline so that it retains much of the factory steering geometry.

  7. Increased ground clearance.
  8. Not only are you going to get ground clearance from your bigger tires, if you use a portal lift gear reduction you will get an increased height of 4"-6" depending on which lift you choose. This is a big advantage that you won't get by simply putting in a transmission gear reduction kit.

  9. Higher reduction ratios.
  10. Finally, SuperATV GDP Portals allow a greater reduction than any transmission kit. This is really important if you have big heavy tires or need additional torque for heavy rock crawling or climbing. The GDP 4" Portal Lift provides a 30% gear reduction and the 6" GDP Lift gives a torque producing 45% reduction. If you need a lot of torque the only way to easily achieve it is with portal gear lifts.

If you want to know more about GDP Portal Gear Lifts and how to install them, make sure to check out more of our How-to pages. Watch our video located below to find out more about how SuperATV engineers our portal gear lifts to be the best tool on the market for getting back your torque.