The two main reasons to alter the gear ratio of your ATV is to get more acceleration or to get more top speed. A lot of riders will use terms like ‘gear up’ or ‘gear down’ to describe the changes to their gear ratio by swapping out a sprocket for one with a different number of teeth.
You may have also heard people talk about a ‘taller’ or ‘shorter’ gear ratio. But to understand gearing up or gearing down and what it means to your gear ratio, you have to know what the gear ratio is actually a calculation of.
If you’d prefer to skip all the details about gear ratio, there is a chart below you can use to decide what number of teeth you want your sprockets to be. Just remember, the smaller the gear ratio number, the more top speed you’ll get. The larger the gear ratio number, the more acceleration you’ll get.
Gear Ratio Calculations And Terms
To obtain your gear ratio is simple, you can use the chart provided below, or simply divide the number of teeth on the rear sprocket, by the number of teeth on the front sprocket. For example if your rear sprocket had 40 teeth and your front sprocket had 12 teeth. 40/12 = 3.33, your gear ratio would be 3.33.
The term ‘gearing up’ or ‘gearing down’ refers to changing one of your sprockets out with one that has a different amount of teeth, to change your gear ratio. Gearing up may also be called going taller, and gearing down may be called going shorter.
You can gear down by installing a larger rear sprocket (with more teeth) or a smaller front sprocket (less teeth). Gearing down will actually increase your gear ratio number. Gearing down will increases acceleration but will decrease top speed.
You can gear up by installing a smaller rear sprocket (less teeth) or a larger front sprocket (more teeth). Gearing up will decrease your gear ratio number. This will increase your top speed, but decrease your acceleration.
Tire size plays a big role in your gearing. Think about it this way, your gear ratio or ‘final drive ratio’ is changed so your tire rotates more or less per sprocket rotation right. So for every inch you increase your tire size it’s equivalent to 1-2 teeth on the rear sprocket.
Another calculation you could use to give you a better idea is to divide the front sprocket teeth by the rear sprocket teeth, then multiply by tire height in inches and pi. This will give you the amount of ground your tire will cover after one front sprocket rotation.
For example, your front sprocket has 13 teeth, your rear sprocket has 41 teeth, your tire is 22″ tall, and pi is 3.14. The equation would be: 13 / 41 * 22″ * 3.14 = 22.9″
Your tire will travel 22.9 inches for every front sprocket rotation. I know this is getting more in depth than it needs to be, but I find this stuff interesting. If you use this same example, but change the rear sprocket to 44, you will notice the ground covered drops to 20.4″ per rotation.
So we can prove with math this way, that increasing the rear sprocket increases torque and acceleration, but will decrease top speed. With a smaller rear sprocket, more ground will be covered per rotation which increases top speed.
Basically what I meant to say, is that you could effectively gear down your ATV by simply getting larger tires. Larger rear tires will increase acceleration and decrease top speed. While smaller rear tires will decrease acceleration and increase top speed.
Best Gear Ratio For Different Terrain
This really depends on personal preference, but gearing down has always been recommended for tight trail riding and track riding. If you’re going to be cornering a lot and need to slow down and accelerate often, it’s best to gear down to increase torque and acceleration.
Gearing up is great for open stretches and straight-aways. A lot of people that plan to race their quads in straight open areas will gear up their ATV for more top speed.
I would suggest only changing out your rear sprocket for gear ratio changes if you can. One tooth on the front sprocket is equal to about three teeth on the rear sprocket give or take. It’s a lot easier to make small gearing changes if you only swap out the rear sprocket.
Besides, if you use a smaller than stock front sprocket, you will be causing extra wear and tear on the chain. The chain will need to now make a tighter turn around that front sprocket, which will wear it out faster.
I would only adjust the sprocket by a couple teeth at a time. If you don’t know what you’re doing, you could be making major changes in the way your ATV runs.
If you’re riding through mud a lot, and notice your machine bogging down on you, you may need to gear down a little bit. Be careful though, if you gear down too much, you may notice that you need to shift a lot more often.
With a higher gearing, you will need to shift less, but may not have the power to get out of tough spots. Higher gearing is best for flat straight areas that you have no chance of getting stuck in.
Keep in mind that when changing out a sprocket for a different size, you may need to adjust the size of your chain to fit. If you plan on getting a new sprocket, I would look at new chains as well.
For an in depth step by step guide to change out a sprocket, I wrote a How To Change The Chain And Sprockets On An ATV article to help you out.
Gear Ratio Chart
This chart can be a guide for you to help decide what size sprocket you might want to go with. With more rear sprocket teeth, you are increasing your acceleration. With less rear sprocket teeth, you are increasing your top speed.
It’s important to keep your chain and sprockets lubed up and in good working order if you want them to last. It’s true, the sprocket teeth wear down and the chain stretches. But you can help minimize those effects by keeping the chain clean and waxed.
I like to use this Chain Cleaner And Chain Wax Kit from Amazon to keep my chain and sprockets cleaned and working. I like that set because of how easy it is to use the aerosol cans. Just spray the cleaner wipe the chain down, spray some rust protection and chain wax on and you’re good to go.
To find out if you’re chain has stretched you can measure the distance between pins and compare to what’s in your users manual. If you’re replacing your sprocket due to wear, I would suggest also replacing the chain. It’s best for the chain and sprocket to wear together.
If your sprocket looks like this image, replace it. You will notice the teeth on the sprocket wearing out and becoming sharper or scared. If it gets bad enough, it will stop gripping the chain and you’ll feel the sprocket slipping off the chain. When it does finally catch the chain again, it could snap it.