SSDION

After having a lot of trouble making my SS camaro hook, I decided to tune the suspension. I read a lot about pinion angle and everybody seemed confused about why pinion angle is important for traction. Here is what I've found:

Pinion angle has nothing to do with driveshaft and crankshaft centerline except if you don't want any vibration. It's true to say that ujoints angles have to be equal, opposite and minimal between crankshaft and pinion to minimize vibration (Pinion paralel to crankshaft). This relation is mathematic and physic if you want to cancel ujoints angles and avoid vibrations. This is called driveline angles.

On the other hand, I was wondering why Madman wanted to ajust pinion nose down relative to the ground if it's supposed to be paralel to the crankshaft. I discovered that when pinion is pointing down, relocating bracket angle changes relative to the vertical and plants tires into the ground

I did 2 small drawings to understand the suspension geometry with -2 and +2 pinion angle. I discovered that when pinion is pointing down, it loads tires and when it's pointing up, it's unloads tires.

So If you want traction, I think you have to go with Madman technic but you can experience vibrations if drivelines angles are too large. You need to play with transmission support height, body angle, tires height, engine angle to compensate for vibrations and have the best driveline angle you can without tearing up ujoints. But pinion has to stay nose down (-2 deg) relative to the ground. Driveshaft and tranny have nothing to do with suspension geometry and tires loading.

This is just a suposition but I think it makes sense. Maybe i'm wrong but I think it's a good explanation

What do you think about my theory guys?

SSDION
Quebec, Canada

SSDION

Sorry, there is an error on the +2 drawing. Angle is supposed to be 92, not 102 degres

Drowned

Wow, those drawings really cleared my mind about how our suspension works... thanks!

This thread needs more attention

leadfoot4

iTrader: (1)

I think you've got a good handle on it........

purdueranger

iTrader: (11)

nice AutoCAD drawings.

ssvert99

iTrader: (26)

you are correct in your statements, but pinion angle has everything to do with driveshaft/crankshaft angle. these figures are all relative to ride height and the angle of the engine/trans within the car. the main focus is what the car is used for and the particular desires of the driver. the crank/pinion angles being the same are good for driveshaft vibrations and highway use yes, but depending on the ride height of the rearend within the car, it can be either positive or negative pinion angle.
the rearend will lift the pinion when torque is applied in a forward gear, therefore a negative pinion angle is needed to keep the suspension/tires loaded under power. how much angle is dependent on the car. available torque, tire compound, gear ratios, transmission type, suspension geometry, etc., all play a role in what is optimum angle needed.
not all cars are the same, but your average f-body car at stock ride height with some sort of aftermarket torque arm seems to work well at -2* for a starting point. this angle is the difference between the angle of the driveshaft and the angle of the pinion. not to be measured pinion compared to the horizon.

sdm1234

iTrader: (8)

im looking at the drawings (which are quite nice!) but i have one question. the relocation bracket angles are different in each picture. does adjusting the torque arm alter the angle of the bracket? i was thinking that it was a static component. also, are the relocation brackets for the LCAs? what about factory brackets?

leadfoot4

iTrader: (1)

Yes, altering the pinion angle changes the angle of the LCA bracket because the brackets are welded to the axle. As you rotate the axle by adjusting the pinion angle, the LCA brackets rotate also. It doesn't matter about the relocation brackets, because they are attached (welded, usually) to the OE brackets, and just allow the LCA to attach in a lower position.

sdm1234

iTrader: (8)

thanks leadfoot4 it makes a little more sense to me. but how does the axle rotate? isn't it just a solid piece that only moves up and down, not pitch-wise? please help me... i'm confused...

djsanchez2

iTrader: (14)

Good write-up. A visual seems to be of more benfit to alot of people.

Sdm1234- When you adjust the pinion angle, it moves the nose of the entire rearend either up or down. Since it is one solid unit, when you adjust the nose down it tilts the entire thing down, affecting everthing attached to it. This includes springs, shocks, phb, etc. (Hell even the caliper moves position slightly.) Thats why madman makes those lil shock relocation tabs so the shocks do'nt bind or break when an aggressive angle is needed.

sdm1234

iTrader: (8)

thanks djsanchez2. i didn't know the nose of the rear can tilt. everything is starting to fall into place in my head now haha.

stangkiller

i keep seeing -2 deg for stock ride height, but what about guys (myself included) who have lowered cars?

djsanchez2

iTrader: (14)

It will be the same. It will just require more adjustment to achieve the -2 degrees. But that is just a base line number. Cars with more play in the suspension generally like a lil more angle. Mine for example like -3.5 degrees unlowered. When it was lowered it liked -2 through -2.5 degrees. And this is going w/ Madman's method of setting the angle.

From what i understand the bushing type has more effect on what your suspension will like anglewise.

Stock rubber = more angle
Poly mounts = mid range
Solid mounts = less angle

^^^ That is how it has been described to me. Take i with a grain of salt though, as there will always be a disagreement for a different method.

CutlassRacer

Ditto that, this goes for G-body and A-body GM cars as well.

leadfoot4

iTrader: (1)

SDM, if you have an adjustable torque arm, the lower leg of the arm has a "turnbuckle" sort of deal. By lengthening or shortening the link, with the upper link remaining the same, you "rotate" the axle. This is how you change your pinion angle. After this is set, then the motion is just "up and down".

The OE torque arm doen't do this, so yes, it's just "up and down", as you mentioned.

sdm1234

iTrader: (8)

ok great thanks leadfoot4. i took a look under the car and i understand it now.

Eric95

iTrader: (3)

ok im starting to understand this now..but say you lowered a car about 1.25" with a stock or other non-adjustable torque arm, where would that put the pinion angle?

leadfoot4

iTrader: (1)

I would think that it would take you negative.....

djsanchez2

iTrader: (14)

^^ Nope. Lowering the car will raise the nose of the rearend changing the pinion angle in the positive direction. Learned that by trial and error lol.

leadfoot4

iTrader: (1)

Yeah, but the rear is "rotating" in an arc defined by the torque arm and the LCAs.