Gearing ratios are a crucial setup element in karting. Using different sprockets can change how fast you can go. It’s important to know how to adjust your gear ratios correctly in order to get the results you want, so it’s good to know which size of sprocket is right for your go-kart.
Smaller sprockets will make your go-kart faster in terms of top speed. However, doing so will sacrifice your acceleration out of corners. Larger gearing will have the opposite effect. Therefore, it’s not always as simple as using a smaller sprocket to go faster in a go-kart.
It’s important to use the correct gearing for any circuit. Some circuits suit a kart that’s quick out of corners, while others are better suited to a kart with a high top-end speed. Below, we’ll go into a bit more detail so you can always pick the right setup for each karting circuit you race on.
Go-Kart Gearing Explained
A go-kart is equipped with two sprockets. Due to karts being direct drive (not having different gears), it’s important to get this right. When you look at the rear wheel you will see a larger sprocket at the rear of the chain (behind the wheel) and smaller sprocket at the front of the chain.
These sprockets are round and have small spikes around them called ‘teeth’. The number on the sprocket represents the number of teeth on it, and this is how you differentiate sprockets. So, if the sprocket says 78 on it for example, it has 78 teeth.
Larger sprockets will have more teeth and smaller sprockets will have fewer teeth. Generally, the front sprocket will have 11 or 12 teeth for Rotax engines and between 10 and 12 teeth for IAME ones. The IAME engine can take a smaller front sprocket as it is able to rev higher than the Rotax.
In most cases, the front sprocket won’t change too much. You should mostly focus on the rear sprocket to fine tune your go-kart’s speed.
A larger sprocket (more teeth, shorter gearing) will give your kart faster acceleration out of corners. However, larger sprockets will also cause the engine to top out earlier on the straight, so you will sacrifice your top speed.
Smaller sprockets (less teeth, taller gearing) will give your kart better top speed at the end of the straight, but only to a certain extent. The straight is only a particular length, and the kart can only accelerate up until you need to start braking. Running a smaller sprocket will mean slower acceleration out of corners.
The key is to find a balance between the two where you can overtake on straights but still have enough pull out of slower corners.
Types Of Sprockets
On top of that, you can also find different types of sprockets. You get standard sprockets which have circles cut into the disc. These are durable and get the job done. If you’re focused on performance, you can go for racing sprockets.
These racing sprockets have much larger cut outs in order to make them much lighter. However, this also makes them much more delicate, and they tend to break easily. If you’re planning to run performance sprockets try to stay off the kerbs!
Smaller Gearing Isn’t Always Faster
Smaller gearing will give your kart a higher top speed. However, at some point the straight will come to an end without the kart reaching its top speed. At this point you are sacrificing too much acceleration and will lose out in corners.
Finding the balance in the gear ratios is essential to being fast. But you also need to fine tune the gearing to your driving style. For example, if you are aggressive on the throttle and find that the wheels spin up too quickly you may need to gear down slightly to compensate for that.
Fast And Flowing
Gear ratios will mainly be determined by the characteristics of the race track you are on. If the track is very fast and flowing, you will most likely be running a much smaller sprocket. This is because the lack of slow corners takes away the need for faster acceleration and requires the revs to be kept higher for longer.
Slow And Tight
But if you’re on a slower, tighter, street circuit style track you will be running much larger sprockets in order to get the acceleration out of the slower corners. These circuits also usually have very short straights, so a high-top speed is not necessary.
Drawbacks Of Getting Gear Ratios Wrong
Gear ratios can be easy to get wrong. But at the same time, most people on the track around you will be on the correct gear ratio. As such, when you get it wrong it can be a disaster and you could end up being miles off the pace.
Keep Up With The Pack
Getting the gear ratios right won’t necessarily allow you to produce the world’s fastest lap time, but it will help you to keep up with the pack. Getting the gear ratio perfect is much more difficult, and that could give you the edge on race day in terms of overtaking at the end of the straight.
Having the incorrect gearing can cause you to lose pace in qualifying if your kart is unable to accelerate fast enough out of the corners. On race day you may end up being overtaken by a lot of drivers if your gearing isn’t giving you a high enough top speed.
How To Find The Right Gearing
Finding the right gear ratio can be a real challenge, especially if you are entered into a traveling championship where you race at different tracks from what you’re used to. There are a couple of ways that you can find the right gear ratios.
The first is through testing. This is especially helpful if you’re only racing at one specific racetrack as you will be able to prepare outside of a race weekend. During a race weekend you want to be adjusting setup elements that will give you a bigger advantage rather than trying to figure out the gearing.
Testing gear ratios works best if you have a GPS activated Mychron device. This will allow you to keep track of your top speed at the end of the longest straight. You’ll want to start the gearing higher than usual. You’ll also notice that the engine will hit the rev limiter before the end of the straight (use this as a guide if you do not have a Mychron device).
Keep moving down to smaller gearing until you reach your optimal top speed. You will notice the top speed ‘peak’ when you reach the correct ratio and then begin to decrease again when the gearing becomes too low. This is because you are sacrificing the acceleration at the beginning of the straight (which is also a part of reaching top speed).
You’ll notice that the correct gearing tends to be when the engine just hits the rev limiter for about a second or two at the very end of the longest straight before you hit the brakes. From there you can fine tune the sprockets to give you more acceleration or top end speed depending on what you need or what you prefer.
Ask For Advice
Another way to find the correct gearing is to copy what others are doing. If you have a karting buddy or a coach you could simply ask what gearing they are running. Rivals may be reluctant to give you their gearing set up, but you could still ask for a general guideline and refine it from there.
Another way to find gear ratios for a new circuit is to research it. There are tons of forums and resources on the internet, and you might get lucky and find a set up for the exact circuit you are racing on. Should that fail, you could also try to compare the circuit to a similar one you already know well and use the same gear ratios.
Factors That May Affect The Gearing Ratios Of A Kart
Gear ratios on a kart change depending on numerous factors. These need to be taken into consideration and its important to have a couple of sprockets at the ready in case you need to make a quick change.
Different Tracks And Layouts
The first and most obvious factor that will affect the gear ratios is if there are track layout changes. These can be anything from different circuits to even small layout adjustments such as adding an extra corner or an extra straight. It’s important to take note of these changes and adjust your gearing accordingly.
The second is your driving style. Some drivers have a very smooth and flowing driving style. This allows them to keep the engine spooled and revving at higher RPMs allowing them to reach higher top speeds. Others have a more aggressive and direct driving style that requires faster acceleration. Find your driving style and use the correct gearing for it.
The final factor to consider is the weather. The main challenge will be rain. In the rain, top speeds will drop, which means you will need to run larger gearing in order to get the engine to hit the rev limiter at the end of the straight. However, using this larger gearing means faster acceleration and more torque, which results in more wheelspin. So, you once again need to find the balance.
Just like other parts on the kart, sprockets also need to be maintained. Sprockets can wear out and lose performance over time. You will notice the golden paint chipping away on the teeth revealing the metal underneath.
Sometimes the teeth will also have metallic shavings on them as they begin to wear down. Eventually, the teeth will become worn down and the sprocket will lose its performance and reach the end of its lifespan.
Use Chain Lube
In order to keep sprockets healthy, you need to ensure that you use enough chain lube after driving the kart. This will reduce the friction, which will not only protect the sprocket, but also aid performance. Spraying chain lube directly after driving the kart is more effective as the hot chain will help the lubricant to get into hard-to-reach areas.
Ensure The Alignment Is Correct
When changing your sprocket, it’s crucial to always have the correct alignment. If a sprocket is even slightly askew it can cause a huge amount of damage to it. It’s best to use a laser alignment tool to do this job perfectly.
Tighten The Chain Correctly
Always make sure that your chain is correctly tightened. A chain that is too tight will damage the sprocket. If the chain is too loose you run the risk of it jumping off the sprocket while the engine is running. Ideally you want around 15mm of oscillation on the kart chain, which you can measure with a ruler.
Smaller sprockets will make your kart faster, but only in terms of top speed. Larger sprockets will give your kart faster acceleration but a slower top speed. The key is finding the correct gear ratio for your specific racetrack, so using a smaller sprocket is not always the answer!