slapper bars and pinion angle?

[70wayfarer]

about to set up the 9" into the rear. leaf springs and am going to use slapper bars.
when setting pinion angle, does the effect of the bars need to be considered.
cheers

 

[ssba]

Depends on how loaded or tight the snubber is to the spring.
If this is track only I would mount the snubbers directly under and contacting the front spring eye.
Spring pack clamped at every leaf forward of the axle housing also reduces pinion wind up.
The less it winds up the less nose down you need to be on your pinion.
You could end up with about 4°

 

[jbc426]

about to set up the 9" into the rear. leaf springs and am going to use slapper bars.
when setting pinion angle, does the effect of the bars need to be considered.
cheers

The most important thing about setting up traction bars is to ensure that the rubber snubber is located directly under and just touching the front spring eye. I had to extend the rear bracket on the traction bar to attain this adjustment.

Once the bars are properly installed, then measure your pinion angle. You will also need to know the transmission centerline angle. Under throttle, these two angles should match up as a parallel line, but not on the same plane. This means while at rest, the pinion angle will be pointing downward in relation to the transmission centerline. Mine was set at 2 degrees down, as the bars limit the rotation of the rear end upward under throttle.

 

[RustyRatRod]

No. Pinion angle and slapper bars are not related. Set the pinion angle between 3-7 degrees depending on what you are doing. Race only, closer to 7, street only closer to 3.....anything else somewhere in the middle.

Once pinion angle is correct, then you can set up the slapper bars. The bars are set by how much air gap there is between the snubber and wherever they contact the car. A lot of people modify the snubber adding a length of grade 8 all thread rod to make the height adjustable.

 

[jbc426]

No. Pinion angle and slapper bars are not related. Set the pinion angle between 3-7 degrees depending on what you are doing. Race only, closer to 7, street only closer to 3.....anything else somewhere in the middle.

Once pinion angle is correct, then you can set up the slapper bars. The bars are set by how much air gap there is between the snubber and wherever they contact the car. A lot of people modify the snubber adding a length of grade 8 all thread rod to make the height adjustable.

Rusty, When I tightened up my slapper bars, it clamped down on the springs on either side of the rear end, stiffened the ride slightly and altered my pinion angle upward by several degrees.

 

[RustyRatRod]

Rusty, When I tightened up my slapper bars, it clamped down on the springs on either side of the rear end, stiffened the ride slightly and altered my pinion angle upward by several degrees.

Yup. That's because you put bars on it that do not bolt to the stock U bolts, didn't you? If you get bars that take the place of the original shock plates, you will have a better outcome. But you still only torque them to 45 LB FT.

 

[70wayfarer]

right, i ended up at 5* down based on hp and will see more track than street. car is going on a chassis dyno in next few weeks so i can see what's what and make any corrections with shims.

RustyRatRod, you say the clamp on style slappers will change pinion angle, and not so the bolt on version. am going to fab my own so will use my shock plates for this.
got a 31 spline detroit locker from roush/yates some time ago and just got a strange nodular case. already had strange 31 spline axles. the locker will replace the troublesome auburn pro 9 i was running.

 

[RustyRatRod]

That's right. They change the angle because they attach at different points. Look at these. See how they would replace the shock plates? They are a GM application but you get what I am saying.

http://www.summitracing.com/parts/lak-21606/overview/

 

[jbc426]

Yup. That's because you put bars on it that do not bolt to the stock U bolts, didn't you? If you get bars that take the place of the original shock plates, you will have a better outcome. But you still only torque them to 45 LB FT.

Yes, I would not want the bars to replace my stock shock plates. The bars I have clamp on in front of and behind the stock spring plates. I altered the length of the rear traction bar mount by making it several inches longer to adjust the front rubber snubber so that it was just touching the front spring eye, and tightened them down. Once the bars are in place, I measure my pinion angle.

The traction bars limits how much the angle can change under acceleration. It plants the rear end downward and lifts the body upward. It did stiffen the ride slightly to, but nothing like a properly adjusted pinion snubber or Caltracs.

Have you ever used the style you are referring too? How would you ever adjust the distance of the front snubber to the front spring eye with the style you are referring too? The only way I see that it can be adjusted is by clamping down that front clamp onto the front spring segment, and then you are altering the pinion angle too.

 

[70wayfarer]

i've not used bars before, but they are more common place at the track than the caltraks. shock plate style slapper bars have been around for decades and have been fabricated by racers and rodders for just as long. the clamp ons not been around anywhere near as long.

 

[Dartswinger70]

I had slappers on my Dart. had some know it all tell me I was wrong to run them because they would make the snubber ineffective, called me a Chevy guy ya ya ya STFU is what I told em

 

[RustyRatRod]

I had slappers on my Dart. had some know it all tell me I was wrong to run them because they would make the snubber ineffective, called me a Chevy guy ya ya ya STFU is what I told em

We have some of those on this forum.......but I say use what you can afford and what works. Hot rodders have been doin it for decades. PArts may be for one application or another, but they are inanimate objects. They don't know what they are being used on. Somebody that looks down their nose at a really good build using "other make" parts is pretty narrow minded in the world of hot rodding.

 

[AJ/FormS]

The pinion snubber can work when you set it up right, and it weighs almost nothing.But for street you can't drive very far and not feel it.Speed bumps are killer; flinging the body up, which then crash lands on the other side. So you end up getting an adjustable one. And then it's a PITA having to adjust it all the time.
Slapper bars can be adjusted pretty easily and do not need the huge range of motion that the P-snubber does.Yeah they're quite a bit heavier, and you'll probably feel them back there,But no more squirming underneath to crank up the alternative.At 63 there's not a whole lot of squirming left in me.