devinsixtyseven said:
Bob-
I have a bazillion questions and probably don't even know how to ask them properly
.
Could you elaborate on track width's effect on under/oversteer? For instance, if you have a given wheelbase, and extend the track width several inches, how is over/understeer affected? What if you extend the wheelbase? How about both at once?
Thanks,
Sean
To answer completely, we would have to get into a book size post and I am not sure most on here would appreciate me going on that long...so let me be brief, and if you have further questions, feel free to PM me and we can keep it off the main board.
That being said, generally, the track width is one of the major stability factors of a vehicle of any type, by it's relationship to the moment arm length between the combined roll center of the front and rear suspension, and the center of gravity of the loaded truck. In other words, for a loaded vehicle there is an axis running front to rear through the vehicle that represents the center axis the vehicle will roll around when a lateral force (side force from cornering, for example) is applied to the CG of the vehicle. Many people believe the force is applied to the ground contact patch of the tires, but this is not true. The ground contact patch of the tires is the resultant of the vehicle geometry.
When you widen the track width of a vehicle (assuming no other changes to the suspension geometry) you increase it's natural stability (giving what most racers call "understeer") because the length of the CG moment arm trying to roll the vehicle over becomes less, in proportion to the track width. For example, you have a vehicle with a moment arm of 12 inches and a loading of 2000 lbs. The example track width is also 12 inches. In this example, you have a force of 2000 lbs trying to turn the car over, because you have a slope percentage of 100%, or an angle of 45 degrees. If you widen this track width to 10 feet, you now have reduced the effort resultant to just 10%. The loading is still the same, you have just applied it over a longer distance. This wider distance forces the effort required to turn to increase. To illustrate this, think of a dual rear wheel pickup. Generally, the track width on the front axle is wider than the duals (dual track is measured to the midpoint distance between the tandem ground contact patches). By removing the outer rear tires and wheels, you have drastically decreased the rear track width and, for the same loading as in the example, now will cause the tail of the truck to become very "loose" and easily break traction in a corner, while the front end will "plow" off a corner in a straight line.
Be aware this is a VERY simplified explanation, and is ignoring a BUNCH of other inputs.
Best regards,
Bob Sheaves
CEO
catNET Incorporated
http://www.catnetsolutions.com
