[sogone]

Trying to wrap my head around something

My Zook is spoa. It has stock shackles and stock springs. Will I have to change the bump stop length?

[mnemonix]

You'll find under full compression you'll still have ~3" of gap between your spring and bump stop.
If you extend the bump stop so that under load the cars weight rests on them, it will feel a hell of a lot more stable under articulation, dropping into holes and particularly when loaded up on side angles.

Without extending the bump stops you run the risk of catastrophic shock failure and premature spring sagging.

[sogone]

What size extension should I use? The spring from my understanding that is opposite to the one being lifted with be concave to tuck the wheel into the guard. What degree of concave is acceptable? In a perfect world the spring shouldn't go further past straight yeah?

[mnemonix]

Most people talk of a flat spring being best suited for SPOA applications.
After being SPOA for a few years, I've found that this would reduce my flex substantially.
My front bump stops are mounted on 50mm SHS spacers directly below the chassis. The rears are the same height, but inboard inside the chassis rails for slightly more "tuck".
This seems to give a good compromise between up travel and spring life. The springs can travel around 1.5" above flat.

I ran for quite a while in SPOA config with no bump stops, but it feels incredibly more stable once adequate bump stops are in place.

Flex your car up and see what it's capable of. You'll soon see where your bump stops need to land.

[alien]

spring life on a SPOA is a mute point... flat leaves are where its at =)

my bump stops in the front stop the tyres scrubbing behind the headlight... my rear doesnt have bumpstops anymore - it was bottoming out on them all the time so i took them out with plans to put smaller ones in, but the lack of weight in the ass end means the spring and up travel stops before getting near rubbing.

feels perfectly fine on side slopes etc.

TECHNICALLY i leaf spring shouldnt go past flat - but thats in a "normal" application... sierra's werent designed to be SPOA, so any general rule is out the window now...

[sogone]

Awesome. Thanks onix for clearing that up.