Spohn 399 - Manual (Page 3)

3
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 flat surface where the torque arm mounts to the rear end (this
surface is parallel with the pinion shaft) 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 torque arm 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 adjusting nut, 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 arm at the track or before a race will take almost no time, and no angle finder will be
needed.
Adjusting your Spohn Torque Arm: You adjust the pinion angle by turning the pinion angle
adjuster, (located at the rear of the lower torque arm tube) either clockwise or counter-clockwise. As
you turn the adjuster you will see the pinion nose of the rear housing moving up/down. Moving the
rear housing's pinion nose down will give you more of a negative pinion angle degree, and up will give
you more of a positive pinion angle degree.
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.