Ride Height - Part 2

Recently we had a vehicle that was measured for frame straightness.  We wanted this vehicle to have a 1/4" rake from front to back and 1/4" from left to right.  The measurements were:

Left Front Right Front
4.25 4.50
Left Rear Right Rear
4.50 4.50

Notice that the Right Rear measurement is the same as the Left Rear and the Right Front.  If the chassis were not bent, this could not be possible.  The Right Rear should be 4.75" because the rake was 1/4" front to back and 1/4" left to right.  What we do is notate that the Right Rear is 1/4" lower than it should be and don't worry about it.  Believe me, the chassis doesn't know it's bent.  We've known chassis's that have been wrecked and are almost an inch bent but still handle well.

The front roll center height and distance from vehicle centerline is a very important consideration when deciding on ride heights.  Most of the time people are trying to get the chassis as low as possible, to lower the center of gravity, not realizing that they are raising the front roll center, which is detrimental to the handling of the chassis.  We find out where the front roll center is and determine what affect lowering the chassis will have on it.  We get the chassis as low as the rules allow as long as it doesn't critically alter the front roll center or after the chassis is lowered we put the front roll center back to the way it was.  Once we get the ride height for the front set, we then set the Left Rear ride height.  Normally it is 1/4" to 1/2" higher than the front usually for forward bite and aerodynamic purposes.  The Right Rear ride height is then recorded because if you change it it will upset one of the other heights.

After you have your vehicle at the proper ride height the weights need to be set and when you put it on the scales you find it isn't even close.

Next tip -  more info on ride heights and weight.

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