Spohn FG-604 - Manual (Page 2)

Setting Pinion Angle
There are two angles to deal with:
1) Driveshaft angle
2) Pinion angle
You subtract pinion angle from driveshaft angle to get TRUE pinion angle
Here's how you do it:
First, had you measured your stock drive shaft angle and pinion angle before you removed
your stock torque arm, you would have calculated a 0 deg. TRUE pinion angle. This is how all
cars come from the factory.
Using an angle finder place it on the underside of the driveshaft and record the angle
indicated.
Next, place the angle finder under the pinion yoke and record the angle indicated.
Record both angles from the driver’s side of the car. On the driveshaft anything to the left of 0
is positive, on the rear end anything to the right of 0 is negative.
Subtract the pinion angle from the driveshaft angle. The result is "TRUE Pinion
Angle".
In order to apply preload you need negative TRUE pinion angle. Adjust the upper control arms
so that the front of the pinion goes down; continue to check each angle until the pinion angle
is more degrees down than the driveshaft angle.
We recommend –1 degrees on a mildly modified daily driven car. For high horsepower
applications we have gotten the best results with –2 to –3 degrees. There is no reason to run
more negative then that, it will actually hurt your performance because it will induce driveline
bind.
You don't want to drive around with your suspension preloaded all the time, it's a lot of
unnecessary binding on the u-joints and suspension. It should only be used when racing.
Here's a tip. When adjusting for your TRUE pinion angle, count the number of flats (or the 1/6
of a turn) as you turn the adjuster, to know how many it takes to adjust 1 degree of negative
TRUE pinion angle and in what direction (clockwise, or counter-clockwise). Once you know
that, then adjusting the arms at the track or before a race will take almost no time, and no
angle finder will be needed.
You will quickly learn that it does not take many turns to adjust the angle by several degrees,
so go slowly and check your angles often.