by Carlo Forni
Tech Talk. Chassis tuning – part 1
The main and most important item of kart competition is surely the chassis and its tuning and setup. Engine tuning can give some 3 or 4 tenths of a second of lap time reduction, but chassis setup and tuning can make more than a second of lap time difference.
First step, the choice
Not all chassis are the same. Different constructors produce different chassis with different shapes and materials. It is also true that some constructors have their chassis made by others. Anyway when starting to tune your chassis make a step back, first choose well your chassis. The kind of tires used, the weight limits in the category you intend to race in and the height of the driver are important parameters that need to be considered when choosing your chassis. Usually every chassis producer has different models of chassis for different uses. Some models have a higher basic grip on all four wheels or just at the front or at the rear.
It is true that if we have to use soft tires and are a heavy and-or tall driver we need a chassis that has not too much basic grip. Such a chassis we call generally a “free” chassis. On the other hand hard compound tires need weight and height (to a limit) of the driver and a chassis that has already a very high basic grip. I have verified personally that chassis that have a longer distance between front and rear wheels are much more “free” than shorter chassis.
An even better hint for you is to check directly on the track. Go and see some races, verify which chassis are the winning ones in the different categories and choose amongst the first ones that are the most performing in your category. Verify if particularly tall or heavy drivers manage to be competitive with particular chassis. In particular verify if drivers similar to you for what regards physical characteristics manage to be competitive with particular models of chassis. Use all these indications for the choice of your chassis.
Parameters for chassis tuning
After having chosen the chassis we will have to deal with all its parameters. Some are regulations that can be done once and are difficult to be varied quickly during a race. Some other parameters can be varied changing some components of the chassis and finally, the last ones are parameters that can easily be varied on the chassis.
For example seat positioning has an enormous importance in chassis setup, even though it is usually underestimated, but can be varied mounting and dismounting the seat, sometimes even drilling new holes in the seat. Changing seat position changes weight distribution on the four wheels. The material of such component is also important and can change both in its type and thickness. Usually glass fiber seats are used, but also carbon fiber (stiffer and more expensive) materials have been utilized in the last years.
Rear axle type, thickness and material, is another important parameter. Changing a rear axle represents a change in a component of the chassis, a substitution that is not extremely rapid, but can be done quite easily (especially if the axle is clean with no rust and perfectly straight). Other substitutions of chassis components are the braking systems or only the brake pads (materials can be changed and sometimes performance varies sensibly). Also wheel types can be varied in shape and material (aluminum or magnesium) and front and rear hubs (length and material).
Finally camber and caster angles regulation, convergence, front and rear carriage modifications, front and rear heights, tire pressure, front, rear and lateral removable bars (if present) are amongst the parameters that can be varied rapidly when tuning a chassis.
Regulations for every track
You will notice in all your testing and races that every track has its particular characteristics and your chassis will adapt differently on each of them. So some chassis have better performance on some tracks compared to others. Fast or slow tracks, high and low grip asphalts together with different weather conditions such as hotter or colder, vary the performance of each chassis. Regulations can be done to adapt your kart to the different conditions. So you will never find the perfect setup for all conditions, but surely a base from which to start must be found. Especially weight distribution is so important and can be a good start for your chassis tuning. Start from such a parameter and then understand how every other regulation can act on your chassis performance. Some parameters have greater effect then others on performance. Start from the first ones to obtain good performance and then act on the second ones to reach excellence.