pinion angle

can you set angle with jack stands under rear axle and front lower control arms? doing old school s/s springs 5/7 nose down

Yes.

While it may work, my experience says It’s more likely that the car won’t sit the same on stands as it does on the tires. The dynamics of leverage at the front suspension may be working against you.

Set it on the ground, preferably at race weight with a but in the seat. Measure the current angle of the yoke on the rear end, and the output shaft of the transmission with a simple magnetic angle finder. Do the math to figure the angle like that. Then make the required adjustments at the perches and re-measure.

If you don’t have wheels & tires yet, I’d try to borrow some for a day, or just wait until you can do it correctly.

Only my 2c. Good luck.

Front suspension doesn’t come in to play setting pinion angle - all that matters is the correct weight is on the rear axle. You want the vehicle to be as close to normal as it would be setting on the ground - horizontally speaking.

I’m admittedly and probably splitting hairs, but that’s not totally true. The load on or off the front suspension will be directly and inversely related to the load on the rear suspension. If the rear suspension is not loaded as it would be with the car static on the ground, the pinion will not be at the same angle as it will be with the suspension in the static loaded position. This difference may be very slight, but if you’re going to set pinion angle, especially in a race car, you might as well be as accurate as possible.

AND ….. here we go , ! ! !

Jack stands under the rear is OK PROVIDED you support the front at the front spindle center, to get proper rear axle loading . Both for/ aft position and angle of the chassis will affect rear axle load.

I would get the car ready to race wet (all fluids at race levels) before dealing with and setting the pinion angle. Do that last! Make sure you have the race tires set at the pressure you will run them at the track also, check it with the driver in the seat dressed ready to race also

So what would be the proper degree?

I always set my pinion angle with SS springs around 4*-5*. I also use stiffer shocks, like adjustable Ranchos which tighten up the rear suspension. The theory I follow is that the harder a car leaves, the stiffer the shocks should be for suspension control. Since stiffer shocks can limit separation, you don't need to go to the extreme end of the pinion angle recommendations. Separation is needed, but with shock technology and other mods, the extreme separation you saw in the early days isn't needed. Check the slip-spline angle too - around 2*?

would not be a complete year without the annual pinion angle argument and discussion post !

The perfect ‘angle’ is dead center from the trans main shaft. Of course we can’t get that because of suspension travel but even 1degree uses up HP so try to get zero degrees going down the tract, the most axel movement only lasts about 1-1/2 seconds or less. If you set angle so it climbs to center on launch then it will be angled down the rest of the race, using HP. That’s when it should be centered. If you can watch the vid a dude made of u-joint over angling, big eye opener.

Easy. Cheap. Works.

Like I said before - keep the car horizontal. Jack stands under the control arms or like shown - front tires on a buck.

Depending on the size of your [censored], add your weight to the driver seat doing any front end alignment, pinion angle setup, rear suspension preloads, weight bias setup.

There are plenty of YouTube videos of rear suspension dynamics from launch to the traps showing rear axle windup - I think DiZuster did a few.

CMcAllister - nice set of bucks.

Some 2x4s and deck screws. Have several sets. Any cage work, suspension set up, interior, electrical, plumbing, etc. goes on them. Car is supported correctly and I'm not crawling around on the floor or trying to get under it to turn screws. Scale pads fit. I can get it real close and level on them. No lift supports in the way or running it up and down.

I like to see from 4 to 7 degrees difference between the pinion shaft and the driveshaft being uphill compared to the pinion shaft. The intersecting angle looks like a V,
If the pinion shaft angle is exactly level then the driveshaft needs to be uphill from 4 to 7 degrees positive If the pinion shaft is negative 3 degrees downhill then the driveshaft needs to be 1 to 4 degrees up hill to get the differences you want to have

Good point to keep in mind: If you get d/s rumble on de-accel flatten the angle 1* and try again.
As mentioned spring stiffness and shocks can take a certain amount of diff rotation out of the equation.

Question
If u set pinion angle with a set of 28 inch tall tires and then switch to 30 inch tall tires, what does this taller tire do to pinion angle

Makes them higher off the ground ?

Some things never change

Nothing, unless you raise or lower the housing in the car at the same time.

It doesnt do anything to the pinion angle but it does tilt the whole car more.. puts more weight on the front
end and most likely to cause you to spin more

I need to make a set of these. I have a bunch of 2x4 cut offs I can use up. I might attach plywood around the outside to eliminate any chance of the wobleeze. Is that a word?

Mine, about 25 years old, 1” plywood sides 3/4” top