Shackle Angle- Parabolic Springs (1 Viewer)

[tlc762]

I installed Parabolic Springs from Man-A-Fre years ago when they were closing them out. I was never real thrilled with the shackle angle on the front springs- They were vertical or just past vertical with the hangers in the stock position. (Chevy 350 and old style ARB bumper with Warn 8274 winch) Here is the drivers side shackle...

 

[tlc762]

Here is the passenger side after flipping the shackle mount. Is this too much angle on the shackle to run it?

 

[tlc762]

The weight of the truck is on the springs in the photos above but the bumper/winch are not mounted obviously. Is this too much angle on shackle to run safely? I think there was a problem with the length of the springs from the supplier which is why Man-A-Fre quit carrying them. My rear shackle angles are good because the rear hangers were moved forward previously when the stock springs were re-arched in the nineties (which shortened the eye to eye length of the springs).

 

[Pin_Head]

The shackle angle means bupkus until the shackle inverts or it hits the frame. Fuggedaboudit.

 

[65swb45]

I’m sure by now @Poser has got a few threads in the FAQ on shackle angle. Have you tried looking there?

 

[tlc762]

I’m sure by now @Poser has got a few threads in the FAQ on shackle angle. Have you tried looking there?

Thanks for the referral to the FAQS. I just went through them again and found nothing about shackle angles...

 

[White Stripe]

Flex it out and take pics of the shackles under full compression and post them up. Angle looks good to me but u need to make surety shackles don't get stuck at full compression.

 

[tlc762]

After flipping the drivers side shackle mount today I discovered that it wouldn't work... See the interference between the shackle and the leaf spring bracket (on level ground without the bumper mounted-no way this would flex). In order to redrill the frame rails to move the perches back would require removing the springs since their is no room for a drill with the springs installed. So I decided to just reinstall the shackles for now so I can run it.

 

[tlc762]

This is the shackle angle with the winch and bumper installed.

 

[LAMBCRUSHER]

Why don’t you just split the difference?

 

[tlc762]

Why don’t you just split the difference?

Not quite sure what you mean. There are only two ways I can mount the hangers using the existing holes in the frame. I guess I could have them welded to the frame in a different spot.
Thanks,
Will

 

[LAMBCRUSHER]

It’s only metal.

 

[White Stripe]

You could try it with the mounts flipped and 2" longer shackles. Longer shackleswould reduce the angle and increase suspension flex. But caster will have to be checked afterward as well as ujoints to make sure they arent binding at full droop.

 

[tlc762]

You could try it with the mounts flipped and 2" longer shackles.

I actually thought about using a set of stock shackles with the mount flipped but didn't have any bushings which fit the spring eyes that matched the stock shackles. (The anti-inversion shackles use 5/8" bolts) From what I researched yesterday morning longer shackles would have a steeper angle using the same mounting locations. Also I don't want to raise the ride height any more since I have plenty of clearance with 33x10.5 bfg's (rear fenders were cut/with bushwacker flares years ago) and the wife is 5'2"... plus she likes to let the horses run with the 350 motor...

 

[Pin_Head]

It depends on what you are trying to accomplish. If you want more droop at full extension, then longer shackles can be part of the solution. If you want better “ride quality”, then shackle angle has little effect compared to spring rate.

 

[tlc762]

If you want better “ride quality”, then shackle angle has little effect compared to spring rate.

That was my reason for the rodeo- i understood that the vertical shackle angle was hurting "ride quality" versus having a 45ish degree outward angle on the shackles...

 

[Pin_Head]

That is a specious conventional wisdom tale, but the spring rate has much greater effect on ride quality than shackle angle. If you want a better ride, get a softer spring.

The problem with arched springs like elliptical or parabolic is that if you set the shackle angle 45 degrees backward, then the spring eye hits the frame when the spring compresses. If you have a flat spring, then 45 degrees back is no problem.

 

[LAMBCRUSHER]

@Pin_Head what angle would you suggest for parabolic springs to mitigate the front eye hitting the spring eye bolt at the fixed frame mount?

 

[Pin_Head]

If I was interested in ride quality, I would leave it as is and get a softer spring. With a SBC V8, you have less weight on the front and the spring rate is too high for the weight. The reason people think that the shackle angle has something to do with ride quality is that people buy highly arched lift springs that are stiffer, install them and then they get a harsh ride and they notice that their shackle angle is 90 degrees. They then speciously conclude that the shackle angle caused the harsh ride rather than the stiff spring caused the harsh ride and the shackle angle.

If I was interested in the maximum articulation, I would measure the eye to eye linear distance of the spring at maximum compression and then adjust the hanger location so that the shackle end of the spring is about 2 inches from the frame at maximum spring length. I would use a longer shackle too.

 

[tlc762]

If I was interested in ride quality, I would leave it as is and get a softer spring. With a SBC V8, you have less weight on the front and the spring rate is too high for the weight.

I realize the V8 is about 250lbs less than the original motor but I figured that the ARB catchers mask bull bar and warn 8274 hanging on the front end might adjust for that to a degree. The springs were installed a couple years after the V8 conversion so I don't know what the shackle angle would have been with the stock engine. I kept seeing threads about shackle angle mentioning its effect on ride quality and figured I should address it to get the most ride quality from the parabolic springs. This was also before I found any information mentioning possible issues with overall spring length of the parabolic springs which were also not mentioned by Man-a-Fre on their website when I ordered the springs from the clearance page. I don't know of any "softer springs" that I could use on the truck- in fact I have thought of installing a front sway bar to help with body roll around corners with the hard top on. Thanks to all for all the info and advice, since the springs have been on the truck for several years now I don't think they will settle much more.
Thanks again for all the help,
Will