i am curious if i put longer shackles on the rear mount for my front leaf springs would there be any draw backs to it? i am currently running a 4"suspension lift and will be doing a shalckle reversal on the rear. might do a shackle extention on the front too not sure yet. any help would be appreciated. i am running 36's on a 78 f-250 thank you.

 

If you're planning on putting longer shackles on the rear after a shackle flip, you'll end up with a little more lift and the pinion on the rear differential pointing up more. This can be beneficial if you've got enough lift already to need it.


I had to make longer front spring shackles for my 95. I already had made a set when I made the shackle reversal, but when I put the banana springs on it, the shackles were too short and would bottom out against the frame and bind. Longer shackles were the only way around that. The higher the arch on the spring, the more the spring extends when compressed. The 3.25" long shackles I had were not long enough to 'absorb' the length change so I had to make a set that were 5" long.

I don't think I'd waste my time with extended shackles with a 4 inch lift. You'll lose some stability due to flex at the bushings and you may end up with pinion angle issues or caster issues on the front. You'll have excessive positive caster on the front axle with extended shackles and your pinion angle may suffer since the pinion will go towards the ground.

Cody

 

Cody pretty much covered the drawbacks, pinion angle can get pretty ugly. I built extended shackles for mine but I also turned my C's to get the pinion where it needed to be and dropped the front mounts a lot too. If you do it just make sure that you use heavy enough material. Mine are 1/2" x 1.5" and about 4" longer than stock.

 

talk about a sweet angle .

 

That's the exact same angle as the stock shackles and those springs are so soft that I don't need it angled like in the back.

 

Ahhhhhhhhhh good point.

 

how about if i just extended the front mounts down some? would i still run into the caster issues. i know if i did the fronts that would turn the pinion up towards the transfer more.

 

I'll see if I can explain it quickly and clearly.

You want to lower the front of the front spring mounts/hangers, correct?

Ok, about caster change:
Positive caster is needed to maintain directional stability (wandering) and return-to-center (after a turn) characteristics of the truck. In Laymans terms, positive caster is the relationship of the upper and lower balljoints (or kingpins) in which the upper joint is farther rearward of the lower joint.

Too much positive caster (it takes A LOT) can cause directional instability, but the most problematic drawbacks to too much pos. caster are hard steering (effort) and balljoint wear/stress. Caster (pos. or negative) will always cause the front of the vehicle to raise and lower when the front wheels are turned vs. straight. However, positive caster will raise the vehicle's front end when turned while negative caster will lower the front.

This is where gravity and directional stability come into the picture. With positive caster, the vehicle's lowest height is achieved with the wheels pointed straight and return to center and directional stability are improved. With negative caster, however, the lowest vehicle height will be with the wheels turned and gravity becomes the enemy, trying to turn the wheels to get the vehicle lower. This is why too much negative caster causes wander and can induce death wobble......or why a few more degrees of positive caster can eliminate death wobble.

You're going to run into closer-to-negative issues by lowering the front hangers. Your best bet will be to lower both the shackle and hanger to maintain as close to factory caster as you can. Remember, too little positive caster isn't good, 0 degrees is worse, but negative is BAD.

Cody

 

In addition, since I'm bored out of my skull......
Thrust angle is like an imaginary line between the rotational centers of each ball joint. Positive caster will project the thrust line in front of the tire, while negative caster projects the line rearward. The angle of this 'thrust' gives stability by 'forcing' the tire to stay straight. Ever watch shopping cart wheels (casters)? What happens when you push them too fast? They begin to wobble. That's typically not a design flaw or bad wheel. It's just the fact that there is no directional stability due to the negative caster. A motorcycle uses positive caster for stability (only the thrust angle is called rake) and most exhibit very good handling. Same goes for the knuckles on your truck. The upper pivot point has got to be behind the lower to create a forward thrust angle.

Caster in itself is not a tire wear angle. In straight-ahead position, caster does not wear tires. However, extreme caster in either direction can cause severe wear during turns. Think about it. If the tire is on the outside of a rotational angle (caster angle of the knuckle), the tire is going to lean on it's edges during a turn. With wider tires it's way more noticeable (and also the reason that tons of positive caster stresses ball joints badly) to see the tires lean during a turn.

More to come in the next installment.......
Cody

 

Good info Cody

 

Thanks. I get bored and my mind starts going a million miles an hour. You should have seen the post I about .......posted regarding ignition systems and inductance, saturation time, and (gasp) ballast resistors (now there's old school!!)

Cody

/will work for reputation points

 

And you desverse some for all that . I know what you mean about a wondering mind, wait about a 8 months and you guys will be wondering what the ehck i've been smoking when saying that your 4340 shafts are no stronger than a common 3/4 wrench (which is true BTW).

 

to.....much......info.......brain.......not....... .responding.

wow and here all along i thought there were just a bunch of dumb rednecks like me on this site!!!!! now i feel really stupid lol. thanks for all the great info though. your like a walking tech book. lol.

so basically my best bet is to drop both hangers for the lift in order to keep the optimium amount of camber. gotcha! thanks for the help though!!!

 

hmmm I found it a little difficult to keep up with all the info that was just spewed out...BUT I think I understand the basics. I have a question since I have original shackles and hangers on my truck and just added a 6" spring lift my rear hangers look like this..


Is that bad? And when the spring starts to compress won't it just cause it to hit my frame? How would I possibly fix this if it is bad?

thanks

 

The picture is super dark so I copied it and brightened it up in my picture program. It's still really hard to see, but it appears as the shackle is pointing very drastically toward the front of the truck .

The things that are going to happen here is:

When the spring compresses it will effectively get longer. This will not allow the shackle to come straight up (impossible for the spring to shorten when compressing). However, every bit of road force is going to transmit directly to the frame (and your seat) since the shackle CANNOT move. The vehicle would have to RISE to allow the shackle to pivot over center to absorb the spring's tendency to get longer...that ain't going to happen (good friend gravity). The spring in the picture does not have enough arch to go 'over center'. You will hate the ride.

When the spring is unloaded, it will not droop. Since the shackle is at the point where it is at it's "longest" (adding to spring length), there is no travel forward to allow droop.

As the spring sags, it will get longer and help your shackle angle situation...however I do not believe you'll get a subtantial length increase from your marginally arched springs.

You are in kind of a predicament here. Those shackles are not easy to move (that style anyways). I think if faced with this issue I'd either get a new set of springs made and alert the manufacturer that they are not long enough. Or I would re-drill the front spring hanger (or add enough material to the front hanger) so that you could move the entire leaf spring assembly back at least 1.5" This will move your front axle back though.......

Someone else might have some other ideas.

Cody