1QUIKWS6

iTrader: (61)

When I installed my Spohn T/A I already had an appointment for an alignment - so I figured I'd leave it up to the shop to set my pinion angle since they could drive the car up on their low rack easier than if I had to jack the car up all around and keep it level with suspension loaded.

Well now I have a vibration at 70mph, so I properly raised the car, made sure it was level and suspension was loaded as if on the ground. I measured the DS angle and got (2) degrees (pointing down to the ground), then measured the rear angle by placing gage on flat mounting surface of T/A mount on rear and got (0) degrees.

To get True Pinion Angle you subtract the rear angle from the DS angle so:

(2)-(0)= (2) degrees TPA

So I say WTF, this is way off from the -1 or -2 degrees I should be running? When I call the shop he claims he is correct because the (2) degree DS angle is really (-2) since it's pointing to the ground, hence:

(-2)-(0) = (-2) degrees TPA

I still say I am correct and that you don't impart a negative sign to the DS angle just because it's pointing to the ground - besides that, I had no vibration prior to him setting the angle.

My contention is that I should adjust the T/A so that the rear is actually pointing down to the ground in front by (3) degrees to get:

(2)-(3)= (-1) degrees TPA

Which one of us (if either) is correct?

TIA,
-Jay-

ninobrn99

iTrader: (8)

if i read this right, you got it right.

Bud M

iTrader: (1)

From a 0 angle, you would adjust the torque arm moving the pinion downward to the desired setting. So it sounds like they did it right.

UMI Performance

iTrader: (77)

Jay,

It sounds like the garage has it right. The vibration over 70 MPH is common with a negative angle and assuming this is a tunnel mounted torque arm. You may have to run this at 0 degrees on the street to get rid of the vibration and set it when and if you go to the track.

Hope that helps,
Ryan

No Juice

iTrader: (11)

I thought pinion angle was determined using the transmission tail shaft and not the drive shaft? Ryan can you shed some light on this?

1QUIKWS6

iTrader: (61)

The instructions for setting the Pinion Angle direct from Spohn tell you to measure the DS angle and the rear angle at the flat area where the torque arm mounts and subtract the rear angle from the DS angle.

I know there are quite a few different methods of how to find the angle - I just went by the instructions from the mfg. of my T/A.

SleeperD

iTrader: (1)

You add the angles, not subtract, so its -2+0=-2 (unless your instructions say otherwise )

Good article here. http://www.carcraft.com/howto/91758/

1QUIKWS6

iTrader: (61)

And there in lies the problem! Here are the directions for setting PA straight from the instructions included with the Spohn T/A:

"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, no suspension bind.

Using an angle finder place it on the driveshaft (a flat smooth spot) and record the angle indicated.

Next, place the angle finder on 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.

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.

Good luck with your new Spohn Performance, Inc. torque arm. We wish you turn lovers the highest of G's, and all of you drag racers the lowest of 60' times!"

So WTF! You ask 10 different people how to set PA - and you get 10 completely DIFFERENT answers. I'm mean, holy **** - this ain't rocket science - it's a simple adjustment

Why oh why can't there just be ONE correct way to do this??????????????

Steve in Seattle

THANK YOU!

I damn near drove off with a -11 PA. :p

Spohn's products are great, but those damn directions just arn't nearly as informative as that one picture in the article.

Yes, I get that downwards angles are negative, but subtracting negative's is equal to adding a positive... my set up could have been real ugly (Thankfully it looked so horrid I wouldn't dare drivce it that way):

DSA = -6
PA = -5

TPA = DSA-PA
TPA = (-6) - (-5)
TPA = (-6) + 5
TPA = -1

See how screwed up that is... why the hell can't people just SAY the damn driveshaft should make a 179 degree angle with the pinion centerline... vertex pointing downwards of course. Could have saved me a damn hour on the net figuring out that no one uses the damn frickin naming conventions.

Time to crawl under the bird and tool that TQ Arm back to reasonable numbers (like -4 and +2)... thankfully I read the Helms manual and it said the working angle (which apparently is what everyone keeps calling a True Pinion Angle) should never exceed 6 degrees.

*sigh*... glad I got that off my chest.