Rear track width has a huge effect on the general handling of your kart. However, understanding rear track width can be extremely confusing. This is especially true when you go online and find all kinds of contradicting theories on what adjusting the rear track actually does affect.
So, how does rear track width affect a go-kart? These are key things to consider when adjusting rear track width:
- Understeer vs oversteer
- Hopping and bogging down in corners
- Testing and how to adjust your track width
This article will go into detail about kart mechanics and the forces that apply to the way in which a kart behaves on the track. I will however also provide simpler explanations if you prefer to have a quick answer for rear track width.
What Is Rear Track Width?
Firstly, lets investigate what exactly we mean when we are talking about rear track width. Track width is the measurement between two wheels. In this case, it is the measurement between the two rear wheels, measured from the outer edges of the tires.
Track width measurements are very important to the setup and balance of a kart. It hugely affects the behavior of the kart while it is out on track. Adjusting your track width is about finding what works for you in each situation. Below, we will discuss some variables that need to be considered when adjusting rear track width.
Understeer vs Oversteer
Most drivers know about understeer and oversteer. These are the most key factors when it comes to finding the right balance on the kart. Moreover, this balance of oversteer and understeer is based on personal preference of the driver and on their driving style.
Smoother drivers, like Jenson Button, will prefer understeer, whereas more aggressive drivers like Lewis Hamilton tend to prefer oversteer. There’s no right or wrong end of the spectrum, it’s all about what makes you as the driver more comfortable in the kart and what allows you to go as fast as you can go.
A simplified explanation of these terms: understeer is when you turn, but the kart wants to go straight. The front tires lose grip (traction) and the kart struggles to turn in, drifting more towards the outside of the circuit. Oversteer is when the rear of the kart wants to pass the front end. The rear tires lose grip (traction) and you are essentially drifting.
Understanding this is crucial for the next section! So how does your rear track width affect oversteer and understeer? Well, there is a short and simple answer, and there is a longer, much more detailed answer.
The short and simple answer is: Widening your rear track width gives you more understeer (more rear grip), narrowing your rear width gives you more oversteer (less rear grip).
At the end of the day, you need to fully understand the mechanics of the kart and the different variables to understand why your kart is understeering or oversteering. This is because some people find different results when making the same adjustments, due to the different variables involved.
In order to fully understand what you are doing when adjusting your rear track width, you need to understand how your inside rear tire is lifting off the track. This is the rate at which that wheel lifts (speed) and the duration of time which the wheel spends off the ground.
I should add that having your inside rear tire lifting off the ground is a good thing. If you watch the top karting drivers, you can sometimes very clearly see that wheel lifting off the ground. This is how you get your kart rotated around a corner in the fastest way possible. But it’s not just driver ability, it’s about having the right setup.
Understeer is when your inside rear wheel is not lifting enough, whereas having too much lift, too quickly will cause oversteer and a “snappy” turn in behavior. Try to keep this in mind when adjusting your track width. Also keep in mind that it works in relation to your front track width, so only adjust one at a time otherwise you will lose your kart balance completely.
If you have too much oversteer, you need to widen your rear track width. This means that your kart will have a lower center of gravity, and therefore it will be harder to lift that inside rear wheel.
On top of that, the wheel will also be lifting more slowly, causing more understeer throughout the corner. Widening the rear track width will expose more of the rear axle. This means it becomes softer and more flexible which equals less grip.
In other words, widening your rear track width gives you more understeer, which means your kart will be more stable but have less cornering force (i.e. grip). You have less grip because you are lowering the force that pushes the rear tires into the ground.
Narrowing your rear track width will give your inside rear wheel more lift and cause oversteer. The higher center of gravity caused by a narrower rear track width will give the kart a quicker and more responsive cornering ability. You will find your kart increasing in rear grip the narrower you make your rear track width.
When your track width becomes too narrow, it can cause an overload on the outside rear tire which will cause a sudden loss of traction and you might find yourself either spinning or having to constantly catch the oversteer.
Karts with narrower road track width feel a lot more unpredictable through corners and they become more difficult to control when driving on the limit. They will also become more prone to hopping through corners.
Hopping Or Bogging Down Through Corners
My kart had a problem of bogging down in tight hairpin corners for a long time. I never had a quick exit out of hairpins. I tried different driving styles and looked up YouTube videos to try and figure out what was wrong with my driving technique.
I was adjusting a lot of different elements on the kart to try and solve this problem including the power valve, carburetor jetting, and tire pressures, but nothing seemed to work.
I could still see all of my competitors accelerating out of the hairpin at almost double the pace I was. It was incredibly frustrating to physically see myself losing three tenths of a second per lap just through one corner. The one variable I did not adjust is the rear track width, and this is a common solution to that exact problem.
Another issue which can be caused by running the wrong rear track width is the kart hopping through corners, this can also be caused by bumpier circuits. In both these cases, it is advised to increase the rear track width until the issue is solved. This you will need to do through testing, but more on how to do that later.
As mentioned earlier, widening the track width makes the axle softer and more flexible in order to absorb the bumps and reduce the hopping effect through the corners. This is also useful advice when it comes to bumpier street circuits.
Weather can play a role in which track width setting to run on your kart. Different weather conditions mean that you need to adapt your driving style and kart setup accordingly. Some will need more oversteer and some will need more understeer.
Colder weather and slippery track conditions will require you to run a narrower track width because of the lack of grip caused by the colder track surface and cold tires. Running the narrower track will increase the rate of lift to the inside rear tire and allowing the kart to rotate as quickly as possible.
When the weather is hotter and the track surface is stickier, increasing your rear track width will give you more grip. These are all dependent on weather and track surface conditions, so be sure to make small adjustments to your rear track until you are happy with your setup. I will further discuss this in the next section on testing.
Testing And How To Adjust Your Kart’s Track Width
Adjusting rear track width is something that the majority of drivers and mechanics do with their karts when setting up for a session. Some newer karts, like the CRG Heron, have a new chassis design which allows for quicker and simpler adjustment of the rear track width.
On many other karts though, it needs to be done the usual way. This is done by loosening the wheel hubs and sliding them either in (narrower) or out (wider) along the rear axle. If you do this, be sure to use a tape measure, from the outsides of one rear tire to the outside of the other rear tire. Move both rear tires the exact same amount, or your kart will be unbalanced.
Using spacers on the inside of the wheel hubs can help you to accurately measure how much adjustment you are making.
So, when testing your different rear track width settings, always make your adjustments by 10mm at a time (5mm on each wheel). This is the general recommended amount of adjustment, and you should be able to feel the difference in the kart with each adjustment. Always keep in mind that the maximum rear track width as per the regulations is 140cm.
This section will contain a quick problem and solution section for you to quickly reference how to adjust your rear track width. In each situation, it is recommended that you make your adjustment by 10mm (5mm on each wheel).
Problem: Lack of traction when exiting corners. (Oversteer after the apex of the corner)
Solution: Decrease rear track width
Problem: Oversteer upon corner entry. (The kart is loose and sliding before the apex of the corner)
Solution: Increase rear track width
Problem: Understeer through corners.
Solution: Increase rear track
Problem: The rear of the kart bounces (hopping)
Solution: Increase rear track width
Problem: Bumpy circuit
Solution: Increase rear track width
Problem: Kart lifts too much (front and rear inside wheels lift off the ground)
Solution: Increase rear track width
Problem: Cold weather conditions and slippery track
Solution: Decrease track width
Problem: Hot weather conditions and sticky track
Solution: Increase track width
Rear track width has a huge effect on the general handling of your kart. Many people get it very wrong because they do not understand it. It can be very complicated, and many people can get different results. This is why you can find so many contradicting articles and forums online.
Always remember that there is no single correct setting, each driver is different, and you have to find your setting that suits your driving style. My best advice is to take a few days where you will have consistent weather and no interruptions and just focus on finding your ideal rear track width.
Do not tamper with any other variables. Just change the rear track width little by little and see what it does for you. Write everything down, from the temperature, to your setups and lap times, and how the kart felt to you and keep that for a future reference.