Setting full bump and shackle angle questions

[Abusfullofnuns]

i posted this in my build thread, but since my window to decide is small, I’m going to post here too.

ORD 4” springs, 6”shackles, 1” body lift

Flexing front by lifting rear. Bump stops not functional.

I’ve got some questions:

How far negative arch(if any)should I be setting as full bump? I still need to figure bump stops out and it won’t be this week.

How does the shackle look? Should it be swinging further to the rear at full bump?

Front compressed with the beginnings of negative arch in longest leaf.


Compressed a jack stroke further and full lock. Needs a hair more trimming.


Same pic but rear view, but one less jack stroke.

Shackle angle and view of the negative arch. The next stroke or two sent the shackle back a bit further. Didn’t want to push the springs any further.



High side.

 

[ChrisPerry]

Ask @Stephen he designed the springs and will tell you exactly how far they will flex without damage to the spring.

As far as shackle angle goes, do a search for shackle angle and user Stephen. He did a very in depth explanation and how to a couple years ago.

 

[Abusfullofnuns]

Yeah, I’m definitely going to have to wait to install the shocks. I just went out and cycled it again. I’ll call Monday if I can make time.

The ride height shackle angle is somewhere in the 12 degree range. Probably fine, right?

However, when compressing the springs around 4 inches of uptravel and it’s negative arched AF. It may be fine, but I’m definitely not going further at this point. It made me so nervous that I didn’t even take time to get a pic. I hit the hoist a few more times and walked to the front. When I saw the spring, I ran right back and dropped the hoist. Ride height axle tube to bump stop bracket was 13 1/4 on passenger and 12 5/8 on drivers.

These are the 10 leaf versions that I believe he has referred to as the “Cummins” version through different posts here on CK5, as well as in a PM.

 

[1-ton]

I was going to take a wild guess that 4" of gap between the bump stop and where it hits. I have been thinking of the same problem with my truck. I have about 9" of lift on the front of my truck, and to get 4" of gap between bump stop and where it hits is a lot of bump stop spacing.

 

[Hogback Fabrication]

The springs are good for 5" to 5-1/2" of compression travel from ride height.

The negative arch thing is no problem at all. The springs don't care what shape they are, you just need to make sure they don't go much more than 5" from ride height so that they last.

 

[Abusfullofnuns]

Thanks @1977k5
I guess I’m just gun shy from a previous experience. I had a front leaf spring snap on an old FJ-40 that I had. It was on a super sketch downhill and nearly caused a multiple end over end rollover. Luckily I rolled into the bank on the first endo and my cage dug in long enough to get a winch on my undercarriage.

 

[ChrisPerry]

Remember that most poly bumps will compress to 1/2 their free height. So allow for their compression when setting it up.

 

[Abusfullofnuns]

I wasn’t super clear with my original post. I’m actually at the stage of mounting the shock towers. I don’t have a solution for the bumpnstops yet. I’ll probably need to move the bracket forward at a minimum or something totally custom.