



Once a car is in motion, the vehicles static weight will move around in a dynamic nature to all four wheels through either one or a combination of acceleration, braking and cornering forces. It interacts through the unsprung weight proportion (as this is what is actually sprung) and the centre of gravity, roll centres of the suspension system. All these forces are ultimately transmitted through various suspension components and either resisted or controlled, in an aid to download on the tyre´s contact patches.

This is why static weight is so important to get right in the first place. As discussed in the static weight page, if we do find out we have a less then perfect weight distribution, it is possible to make suspension tuning adjustments to counter act these in balances. Sometimes the static weight might change due to off track diversion, will sequential damage or misalignments to the car.

If we are not designing a racecar from the drawing board with advantageous weight distribution in the first place, what can we do?

We can use corner weighting to adjust a single spring perch and either make it shorter or longer (adjusting ride height). This changes the car´s static weight distribution. Normally it is better to set minimum ride height settings, which will stop the car bottoming out. This way any adjustment to corner will be increasing height and not compromise the suspension system too much from bottoming out.





Static Weight:

If we take a static car which is fully loaded with all fuels, oils and driver on board, ideally we want equal corner weights distributed equally across the car (50% left, 50% right and at the front and rear of the car).

While the overall car designs drive line layout will play a fundamental importance in the total fore and aft static weights, it is possible to still make some changes to increase this ideal balance harmony (normally through moving components like batteries, fuel cells etc.).

It is always best to to get your static weight measurements in the first instants before making any radical suspension changes. This can be calculated with digital scales designed for the job, and will best be done when new suspension components are fitted to the car.





Drive line and Static Weight.





Front Wheel Drive (FF)= more weight over the front of the vehicle, normally 60:40 split.

Front Engined, Rear Wheel Drive (RF)= tend to be very balanced with 50:50 split possible.

Mid Engined, Rear Wheel Drive (MR)= more weight normally over the rear of the vehicle, 40:60 split.





As soon as the car is in motion, the car's weight will act through the centre of gravity and affect the suspension's roll centre. During acceleration, braking and cornering loads, this is when any uneven static load rates will transmit themselves into understeer or oversteer handling characteristics.





Bear in mind the following rules:





If we increase the FL(front left) and FR (front right) spring perch (adjustment ring), then only ride height increases.

If we increase RL and RR spring perches, then only the ride height increases.

If we either increase the FL and RL or FR and RR ( one side of the car), we only increase the ride height.





Uneven Weights:

If we placed a car on the scales and we could see that the front left (FL) and front right (FR) had a difference of 25 lb/kg between them, this will affect the way the tyres behave under download forces acting through them. Acceleration, braking and cornering (or a combination), will be slightly unbiased and will result in less then optimum performance for the tyre with more weight.

Under Braking the corner with the more weight will be prone to lock up quicker, with cornering loads it will lose traction quicker and side, causing some understeer, also there will be slighter better cornering capacity on one side. With acceleration, the corner with the more weight on, will unload the diagonal rear tyre more, which could cause oversteer tendencies.

Any tyre which is overworked will reach its peak performance quicker, overloading it and raising the temperature and it will also wear out quicker. Corner weighting strive to counteract act these imbalances if not already dealt with in the design stage. The actual drive line layout, tyres and unsprung mass, will contribute to the overall effect to these unbalanced corner weighting issues.





Single Raised Spring Perch:

If we do have an imbalance in the corner weights, we will have to try and even this out, this is done by adjusting a spring perch. If we were to raise a single spring, this has an effect on all the other corner weights.

If we raised the front left corner up, this would have a direct effect on the diagonal rear right corner weight, as it would lower the ride height. The rear right corner would resist the downward force applied to it and additional weight would be transferred to that corner. As the front left and rear right corners are now under more tension (as they are linked from a weight distribution point of view), the front left would also increase its corner weight.

Now that both front left and rear right are carrying more static corner weight and there has not been a increase in unsprung mass. It is logically to assume that the transferred corner weight has come of the front right and rear left corners. As a result they will also increase in ride height, due to the reduction in corner weight acting upon them.

If you have a perfectly balanced car, than you will will want to retain this configuration as it has been engineered into the specifications on the drawing board. Production cars are not perfectively balanced in most cases, from a performance point of view and we can use corner weighting to maximise static weight distribution levels. Sometimes we even have cases of previously balanced cars, running off the track or for other reason becoming cross weight unbalanced. This is where corner weighting can help us out.





Multiple Diagonal Spring Adjustments:

This is where it gets a little more complicated, what if we had the perfect ride heights, but our corner weights were out. We know from adjusting a single spring perch, that it will have an effect on all the other corners, so what can we do?

By adjusting all four corner weights in the same diagonally direction, up or down, we can change static corner weights without affecting ride heights. Effective we are counteracting each diagonal corner while still affecting corner weights.

It is important to know that different vehicle drive line configurations will affect the front and rear ratio´s differently, this is one of the reason to make precise documentation of any adjustments make while corner weighting. Have fun with your corner weighting to achieve the perfectively balance car.





Corner Weight Adjustments, Where to Begin.

Before we adjust the corner weights to get a perfectly balanced car, or as close as is possible under the design constraints, we need to check that the car is race ready and we have the following check list complete:







Tyres (tires) inflated to the desired pressures.

Anti-roll bars (sway bars) are disconnected, as not to add to the springs loading force, which will skew the results.

You have a method of recording the small adjustments , this is very important as it may take multiple changes to get the desired corner weights. It is easy to forget what you have already done on each corner.

Ride height adjusted to minimum levels for suspension compliance if known.

Full fluids in the car including fuel, coolant levels, gearbox oil, power steering etc.

Driver is in position, or is calculated in the final results.

Suspension settings including toe, camber, castor, damping etc.





Changing one spring perch will have the effect of changing the static loading and ride height on all four corners, so it is important to logically approach this. If we change the height of both the front, rear or sides, together, there will be no change in corner weights. Changing diagonal corner either up or down together, will change corner weights but not ride heights.





Setting up the Scales:

Once the car is ready to begin the process of corner weighting, lay the scales out in the corresponding location for each corner. Make sure that the scales are correctly set up as of the manufacturers instruction, all cables plugged in and allow time for them to warm up. Zero the scales to make sure that no weight in registering on any of the corners, also make sure the scales are on a flat surface.

Double check the scales do not need charging, and if possible get somebody else to stand on each scale to make sure you have the same readings and that one of corners is not correct. Paying attention to the scales zeroing back after each release of weight. We should all be ready to start to jack up the car and slide the scales into position. We need to now make sure the car is settled and it is best to bounce the front and back up and down and let the suspension settle.





Keeping records:

We are now ready to begin the spring perch adjustments to optimise corner weighting. It is best to follow the same procedure every time you check the corner weighting on the car. Any adjustments should be thoroughly recorded and the car should be bounced up and down again and let to settle to confirm weight readings. Record as much detail as possible about the whole suspension settings used, this way when lap times are recorded at the track, it can be easier to analyse how different adjustments have impacted pace. Having a chart to record spring turns to height increases can help to save time if you are planning on this process regularly.



