One of the biggest enemies to a great new set up is a weather change. Suddenly a near perfectly handling car can change dramatically when the track conditions change due to a change in weather. However, with a few simple adjustments the effects of the weather don’t have to impact you too much.
How Does a Weather Change Affect Handling?
When you set your car up for track use or racing it is usually given a set up that is used on a dry circuit where grip conditions are ideal. When the weather changes to rain, damp or snow the surface generates a lower friction co-efficient providing less grip and not providing the tyre with as much traction with all other factors remaining the same. Therefore, you are no longer using your set up to its full potential as the cornering, braking and acceleration forces available in dry weather are no longer achievable.
To help compensate for the lack of grip due to the lower friction co-efficient a few tweaks can be made to the dry set up to try and get the tyre working better in conditions with lower lateral cornering loads.
If you are heading out to a track or a race day where the conditions are dry but are looking like it is going to rain or that worse conditions may appear; it is best to head out with a dry set up rather than going out on a wet set up in the dry. This is because a dry set up will usually work in the rain to a higher standard than a wet set up would work in the dry.
It’s not only a weather change in terms of rain or snow that can impact performance either. A temperature change can also affect the performance of your set up. For example, if you are competing in an endurance event where the environment fluctuates in temperature such as very hot daytime temperatures and very cold night time temperatures; this can have an impact on the handling of your car and can be compensated using set up.
What Equipment Is Required To Make The Adjustments?
In order to make the adjustments track side to react to changing weather conditions the following equipment or components are recommended.
The camber gauge is one of the most cost effective pieces of equipment for the benefits gained from owning it. Most weather changes require an alteration of camber to optimise set up so this is ideal. Two main options exist: a Spirit Camber Gauge and a Digital Camber Gauge. The spirit gauge is the cheapest option and is very effective. The digital camber gauge can be calibrated to the ground that the car is sat on to give a more accurate reading on a non-level surface.
Tyre Pressure Gauge
The tyre pressure gauge is the cheapest piece of equipment on the list but the benefits are large. Keeping track of your tyre pressures on the circuit and being able to adjust them adequately is very important when optimising your set up for changing weather conditions.
Tyre Temperature Pyrometer
The tyre temperature pyrometer is in the optional category of set up equipment as a lot can be done with the tyre pressure gauge and camber gauge. However, if you are determined to achieve the best set up possible then it will become an invaluable piece of your tool kit. The pyrometer will allow you to check that camber, toe and pressure changes are having the correct effect on the tyres and allow the final stages of fine tuning the set up to take place to optimise the tyre for the conditions.
Having adjustable dampers is almost a must have for any serious track car or race car. Most dampers come with rebound adjustment if they are 1 way adjustable which is a useful adjustment to have. However, it is beneficial to upgrade to 2 way adjustable dampers at least to allow for compression damping to be adjusted as well.
Adjustable Anti-Roll Bars
Adjustable anti-roll bars are a useful component for weather changes from dry to rain etc as they allow the cornering stiffness of the car to be altered quickly, easily and effectively. When grip reduces some of the main side effects will be mid corner understeer or oversteer. The anti-roll bar will allow the adjustment necessary to help remove these symptoms from the set up in minutes. Therefore it is a piece of equipment that allows the driver to respond quickly to weather changes mid race or mid event in a similar way to the adjustable dampers whereas camber or toe changes could take more time and equipment.
How to Change from Dry Weather to Wet Weather
If you are running on slick tyres then the best option for wet weather is to fit a wet weather specific tyre to your car which will alter the grip levels in the wet in a positive way. However, the below article and alterations are based on a car that is running a track day tyre such as cut slicks or a road tyre that does not have the option to change tyres so instead requires set up alterations.
The most common weather change is from dry to wet when it rains mid race or track day. The wet circuit means that the same cornering forces are no longer available and therefore, the camber set up becomes less optimal due to the camber being set for the stiff set up to allow the chassis to roll onto the tyre. In the wet less chassis roll will occur with the same set up. Therefore, a quick alteration that can be made is reducing the negative camber on the front and rear wheels. A good way to check if you have set the correct amount of camber is to use the tyre pyrometer to check the temperature of the rubber across the surface and make sure that the temperature distribution is similar across the tyre as the dry set up.
One fast option when the wet weather sets in is to soften the anti-roll bars. This allows the car to roll more in corners which will help provide more grip mid corner by reducing the lateral load transfer rate across the axles giving the tyres increased grip. As the cornering speeds are lower and the grip is lower, the car needs a softer set up in roll to give the same roll angle as a dry set up where higher cornering forces are present to act on the car. It is best to soften the anti-roll bar that is attached to the driven wheels more than the other anti-roll bar to provide more traction in the wet on corner exit when the throttle is applied. The anti-roll bars can then be fine-tuned on track. If you do not have adjustable roll bars and have very stiff anti-roll bars it is common in very wet conditions for anti-roll bars to be fully disconnected as that can provide a higher benefit than leaving them attached.
Another set up change that is more drastic than the above two is to install softer coil springs. This is in the case where anti-roll bars are not adjustable or are on their softest setting and are not providing enough roll still. Therefore, installing softer springs allows the car to roll and move more in the corners to provide more gip at the tyres. Another benefit to installing softer coil springs is that the car can pitch and dive more during acceleration and brakes which will provide more load on the driven wheels if the setup is rear wheel drive and will provide more traction in the wet conditions under braking.
If you have adjustable dampers installed then they can be softened in bump and rebound stiffness to allow the car to roll, pitch and dive more. The car will still roll and pitch at the same rate as the dry set up with them softened due to the forces now being passed through the damper being lower, meaning that the resistance from the dampers also needs to be lower to compensate. This will allow more compliance in the corners and allow the tyre to grip in the wet conditions.
Finally, tyre pressures can be altered which is a change that anyone can do with a tyre pressure gauge. There is some debate around tyre pressures in the wet and the truth is that all tyres will react differently in wet conditions. However, in general for track day tyres such as cut slicks or with grippy road tread, the pressures will need to be increased in wet conditions. This is because the tyre has an optimum operating temperature for grip. In wet conditions the tyre is generating less grip and therefore less heat. There is also the added factor of the water cooling the tyre down as it makes contact with the rubber. Therefore, a higher cold tyre pressure is required to get the compound up to temperature on circuit. Another argument in favour of increasing tyre pressures is that the tyre needs to channel the water from the centre of the tyre out to the edges of the tyre as quickly and efficiently as possible. Therefore, a properly inflated tyre operating at the correct hot pressure and temperature will keep the water channels at their designed angles and elevation to move the water away from the tyre as quickly as possible providing more grip. An argument in favour of lowering pressures in the wet is when high pressures are already used to the extent where the tyre is raised at the edges not putting the entire contact patch in contact with the track surface. Therefore, lowering the pressures slightly will engage the tread more and generate more heat due to more rubber being on the surface, therefore generating more grip. However, this is not in most cases.
How to Change from Hot to Cold Track Temperatures
During long races or cars competing in championships that travel the world competing in many different climates it can be common for track temperatures to alter drastically meaning that set ups will require slight alterations to optimise the grip from the tyres. For this scenario we will assume that the car is set up to race on hot track temperatures and needs to change the set up to race on a colder surface. If your car is going from cold surfaces to hot surfaces then these options can be reversed on your set up.
The first and easiest option to increase grip levels is using tyre pressures. The drop in track temperatures will mean that the tyres will not be achieving the same temperatures and therefore not reaching the same hot tyre pressures. As most tyres have a small window for optimum pressures, the tyre pressure can be increased when cold. A good way to know how much to increase the cold pressure by is to measure the tyre pressure of the hot tyre on the hot surface and keep a note of it. When the track temperatures drop measure the hot pressures and compare to your notes. The difference between the two pressures is the amount that you can try increasing the cold tyre pressure by to get you close to fine tune from.
If you have access to a tyre pyrometer and have your tyres generating the optimum temperatures on the hot surface then it is likely that the temperatures will fall on a colder surface. In some cases, when you have adjusted your cold pressures so that your hot pressures on the cold surface are optimal, the tyre temperatures might still be too low. If the distribution of temperature across the tyres is correct then you can increase the temperature of the compound by increasing the amount of toe. This will generate more scrub on the tyre in a straight line, generating more heat in the compound which will help to achieve the ideal tyre temperatures. However, altering the toe in a set up will have dynamic effects so take care when altering toe and refer to our “How To Adjust and Tune Toe” section for more information.
A lot of options have been selected above for changing conditions. Not all of them need to be done at the same time as this could drastically change the handling of the car which in turn could make you slower due to you not being used to how the car handles. It is best to alter a few such as dampers, anti-roll bars and tyre pressures first and get used to that set up. If you feel that you require even more grip in the wet then you can start altering the other options one by one until you find the best wet set up for you and your car.