pinion angle under acceleration/braking

[fidel]

has anyone done any test or have any obsevations on what the pinion angle does under acceleration and braking.

for example on my 142 the rear axle has half a degree of camber and no toe at ride hieght. so im woundering if the pinion angle twist down or up during acceleration. if it tilted down or the rear squats the i would have a slight toe in, or if its tilting up during acceleration or the rear lifts then i would have a slight toe out.

[stylngle2003]

on the dyno, we watched my rear brake caliper on the driver's side go from 2:00 to about 4:30 between a roll and WOT. of course, my dshaft support was shot, and i had stock torque rods, but still. bad juju

[Poik]

if it tilted down or the rear squats the i would have a slight toe in, or if its tilting up during acceleration or the rear lifts then i would have a slight toe out.
Or vise versa?

[Renny_D]

under acceleration the pinion should move the opposite from the wheels - unless you have a vw with reduction gears.- so wheel turning counter clockwise means pinion turning clock wise - pointing up higher. I'm amazed to hear that the axle cam with some camber stock. Is that true for all 142s or did some one do the heat and bend method with yours?

Thanks
Renny

[fidel]

I'm amazed to hear that the axle cam with some camber stock. Is that true for all 142s or did some one do the heat and bend method with yours?

it was like that on my 145 also. i'm not sure if there all like that. it could just be from 30 years of abuse.

[blkaplan]

under acceleration the pinion should move the opposite from the wheels - unless you have a vw with reduction gears.- so wheel turning counter clockwise means pinion turning clock wise - pointing up higher.


Thats exactly what I thought....

[fidel]

under acceleration the pinion should move the opposite from the wheels - unless you have a vw with reduction gears.- so wheel turning counter clockwise means pinion turning clock wise - pointing up higher.

is this due to the bushing flexing ? what about with a no compliance setup(all hiem joints)?
is the geometry of the rear of a volvo(guess i should be more specific a 240) designed with anti squat ?

[blkaplan]

is this due to the bushing flexing ? what about with a no compliance setup(all hiem joints)?
is the geometry of the rear of a volvo(guess i should be more specific a 240) designed with anti squat ?


Use an angle gauge and find out.

[Renny_D]

is this due to the bushing flexing ? what about with a no compliance setup(all hiem joints)?
is the geometry of the rear of a volvo(guess i should be more specific a 240) designed with anti squat ?

Yes mostly due to bushings. If you have a no flex system then that rotation will be transfered to the links to body. It should put the lower in compression and the upper in tension. I don't think it was designed with anti squat as the links are almost paralell but I could be wrong.

Why are you asking about this?

Thanks
Renny

[blkaplan]

Yes mostly due to bushings. If you have a no flex system then that rotation will be transfered to the links to body. It should put the lower in compression and the upper in tension. I don't think it was designed with anti squat as the links are almost paralell but I could be wrong.

Why are you asking about this?

Thanks
Renny

Trying to figure out a preferred static pinion angle for the rear suspension.

[Renny_D]

Trying to figure out a preferred static pinion angle for the rear suspension.

Set the car at ride height and match pinion to most rearward output shaft on the driveshaft. Least that was what I was taught. S'pose to have the least vibration that way or at least the least vibration at the height the car will be most of the time. No bushing is going to mean lots o vibration..

Thanks
Renny

[blkaplan]

Set the car at ride height and match pinion to most rearward output shaft on the driveshaft. Least that was what I was taught. S'pose to have the least vibration that way or at least the least vibration at the height the car will be most of the time. No bushing is going to mean lots o vibration..

Thanks
Renny

You would be surprised how little vibration there is as long as you have balanced wheels and tires. Its not as bad as one would think.

Thats what I would think too but its easier to pick a precise angle if you know the range so you can get the pinion angle centered through the center of the range.

[fidel]

Yes mostly due to bushings. If you have a no flex system then that rotation will be transfered to the links to body. It should put the lower in compression and the upper in tension. I don't think it was designed with anti squat as the links are almost paralell but I could be wrong.

Why are you asking about this?

Thanks
Renny

well they are almost paralell, but do get closer together at the front mounting points, also they are not the same lenght. guess its time to get out the cardboard and a pegboard to see what happens.

besides what bne said, i'm also tring to figure out what will happen with rear toe under acceleration and braking. if i were to have more rear camber than i have the efects on toe in/out will be greater with pinion angle changes.

[blowndrift]

Here's some generalized info gleaned from racing in GT-1 back in the early 90's. On the Ford 9 bolt it was known that due to the carrier bolting on the front of the housing, you would find more toe-in gain under acceleration and less toe-out gain under braking. With the Chevy type rear( and 240 also it would seem) where the nose and axle were cast and gear access was via a bolt on plate at the rear of the housing there was little toe-in gain under acceleration and more toe-out gain under braking.
Perhaps more specific to your question. According to track conditions we would dial in more pinion angle(nose down) when the track was sticky and less angle as less grip dictated.For instance, the least pinion angle was called for in the rain as too sharp a reaction would brake the tires loose. What happens is when power is applied, the axle rotates backwards raising the pinion nose, this in turn through the trailing arms tries to raise the rear of the car which is of course trying to squat down due to weight transfer. The end result is more downforce on the rear tires giving more grip for acceleration.
Hope that wasn't too much of a ramble and actually helps.

[mikep]

On the Ford 9 bolt

9"?