Revision History:

August 15, 2005: LFS Suspension Calc 0.5 
	--first release
August 20, 2005: LFS Suspension Calc 0.6 
	--Total rework of fundamentally broken first version

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Introduction:

This spreadsheet is a very simple calculator to help you set up your car's suspension in the game Live For Speed.

This is not intended to be a replacement for the more famous LFS Setup Analyser by Colcob. This program is just intended to do a few slightly complicated calculations for you, so you can figure out how stiff to make your springs, and how much damping to use. You'll still have to do some work yourself, probably with the aid of Bob Smith's Gear Ratio Calculator (which does all the downforce work for you). I also recommend reading Bob Smith's Advanced Setup guide for information on what this spreadsheet is doing, and why.

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Explanation of fields:

All fields have a space for Front and Rear, which correspond to the front and rear of the car. Some fields are input fields; you put the data into these fields yourself. Some fields are calculated fields; the data in these fields is determined by what you put in the input fields. Some of the calculated fields are data that are shown only for clarity, while others are the output values that you will be putting into LFS.

Force (N): Input Field. The downward force being exerted on each end of the car. This is the combined force of the weight of the car, the fuel, the driver, and any aerodynamics the car may have. I strongly recommend using Bob Smith's Gear Ratio Calculator (which includes a downforce calculator) to get these values. Getting them wrong will make everything else wrong.

Equivalent Mass (Kg): Data. The equivalent mass of the car on each end as extrapolated from the downward force, assuming 1G vertical acceleration, a.k.a. normal gravity. If you are using aerodynamic downforce, this will be greater than the actual mass of the car at a standstill.

Optimum Frequency (Hz): Input Field. The optimum suspension frequency at each end of the car for each 1000 Kg of mass. For racing vehicles, this will probably be in the range of 1.8-2.2 Hz. Lower frequencies result in a softer suspension, while higher frequencies result in a stiffer suspension.

Adjusted Frequency (Hz): Data. The suspension frequency as adjusted for the effective mass of the car, assuming the optimum frequency specified above. If these values differ by more than 0.75 or so, the car may handle poorly and you should consider changing the optimum frequncies.

Spring Rate (N/m): Output Field. The stiffness of the springs required to achieve the adjusted suspension frequency, taking into accound the equivalent mass of the car. Note that the setupd sliders in LFS are in k(N/m), so divide this value by 1000 to get the value you will actually put into LFS.

Critical Damping (N/m/s): Data. The exact strength of the dampers required to bring the suspension to a full stop with neither excess movement or excess damping. In practice this is actually rather more damping than results in best handling, thus the next 4 fields.

Rebound Reduction (%): Input Field. What percentage of the critical damping rate you wish to use for rebound damping. Typical values are 0.85-0.9.

Compression Reduction (%): Input Field. What percentage of the critical damping rate you wish to use for compression damping. Typical values are 50%-80% *of your rebound reduction*. So, if you are using 0.85 for rebound reduction and want to use weaker compression damping, use 50% of 0.85, which is 0.425, not 0.5. This is a very rough guideline--compression damping is usually less than rebound damping, but some racers use more, to achieve specific handling effects.

Adjusted Rebound (N/m/s): Output Field. Strength of your rebound damping, as affected by your rebound reduction. Note the slider in LFS measures this in k(N/m/s), so divide by 1000 to get the value you will actually enter.

Adjusted Compression (N/m/s): Output Field. As above, only for the compression damping.

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LFS Suspension Calc is copyright 2005 to Ian McClure, aka Scarab, aka 5th Earth.

These files may be distributeed freely, as long as both the spreadsheet and this readme document remain wholly unaltered, and are never distributed seperately.