[Cammopricey]

I need a bit of help understanding why spring over is so bad
I many see benefits of doing this lift mainly
•improved spring and shackle clearance
•reasonable wheel travel
•clearance for bigger tyres i hate cutting guards or body lift
I know it not cheap to do this properly that is not a problem i have
So if people with knowledge or past experence please help

[alien]

You've basically covered it... cost versus gains its expensive.

The biggest difference between a guard chopped sierra on 31s and a SPOA sierra on 31s, is that everything above the diffs is 4" higher up, so it will be inherently less stable as there's more weight up high.

That didn't stop mine passing engineering and a lane change test though.

If you're just trying to do something a bit different then go nuts. It worked for me.

If you want to do it for half the price then go the RUF & Guard chop option.

[Reubs]

How do you get any improvement in wheel travel with SOA alone? You don't.

If you want shackle clearance then run standard shackles. Extended shackles generally won't make your car more capable.

[greyghost]

and your in Vic so it is unlikely that you can get it engineered anymore. and if you don't engineer the car it is a very obvious mod, aka defect!

oh and you missed the negative impact the lift will have on your drive shafts and uni joints, SPOA "eats" uni's and will vibrate (something chronic) at speed

i build one twenty years ago, and i would NEVER bother again. I have proved that you can fit a 35 on a standard hight Sierra, with no body lift. and thats about the biggest tyre you can practically run on a SWB sierra.

[alien]

greyghost - if done properly (ie: $$$) then driveshafts and unis are fine. Mines been SPOA for about 6 years now and goes great and is incredibly reliable- and i daily drive it.

You are correct though on those other points.

With the cheapness of after market coil kits etc, and the fabrication skills and chopping required to go SPOA you might as well re-do the entire suspension with coils and links if you're going to the effort of chopping stuff up for a SPOA conversion.

[Red89]

More prone to axle wrap due to requiring a lower spring rate to keep the vehicle low

[jdk81]

If you add trac bar to prevent spring wrap etc you have just done one-two links worth of work (or same work as a radius arms)

If you "can" get it engineered spoa, you are better off getting it engineeres on coils.

You can run radius arms front and rear fairly easily.
Off the shelf parts from other cars means itll be easy to engineer.
Its a better answer.

[Gwagensteve]

Cammopricey wrote:

I need a bit of help understanding why spring over is so bad

I'll play. I'm well known as a SPOA hater. Mostly because the vast majority are poorly conceived or executed. (Alien's being one of the few exceptions) However, there are some ways a SPOA can be built more effectively. Here's my thoughts. I was playing with Suzuki's through the height of the SPOA boom where its was apparently impossible to build a capable sierra without a SPOA. There are better and worse ways of doing a SPOA, but they are always pretty problematic for the gains you get.

Here's my thoughts on your questions.

Quote:

•improved spring and shackle clearance

Hmm, yes, but how much added room you get is dependent on how tall you want the finished car to end up. However, hanging up on the shackles or springs is less of a problem than you'd imagine, especially if you have an appropriate tyre size for the terrain you wish to be driving. At best it's 5", but the reality is if it's 5", your car is pretty tall, and that's a net loss.

Quote:

•reasonable wheel travel

I'm not really sure what that means. A stock sierra, with stock springs, gets all the possible travel from a spring of that length and rate. My guess is that you are referring to the practice of over compressing a spring in a SPOA application. (which is common) This is a very slippery slope. In order to get the springs to heavily over compress, they need to have a low rate. This leads to severe axle wrap and brake dive. the "correct" way to set up a SPOA is to set the bumpstops for the same amount of compression travel as a SPUA sierra with the same springs. This will allow sensible spring rates to be run and you can expect reasonable spring life, but there's no outright gain in travel over a SPUA sierra. There are some other advantages of SPOA- reduced roll stiffness and raised roll centre, but they come hand in hand with a significant increase in centre of gravity.

It's also easy to look at flexed out SPOA cars and be impressed, but they often don't "tuck" their wheels very well at all - end result is just a tall car.

•clearance for bigger tyres i hate cutting guards or body lift

What do you consider a "big" tyre? because a 31 can fit a Sierra pretty easily without a body lift if you space the bumpstops and slide the axle forward a little. How much beyond a 31 were you planning, because at 33 or more you're going to have to work the guards, SPOA or not... and the more flex you allow, the more you have to work the guards, even with a SPOA. Yes, there are some stiff/flexless SPOA cars that can run big tyres... but stiff/flexless SPUA cars can run bit tyres too.

Hmm, this is an interesting one. What makes you think you'll get a big tyre under the car without cutting the guards? The clearance problems with the sierra are at the firewall, and there's no guarantee you won't have to work the firewall and guards at the rear edge of the front guard to clear a big tyre.
In any case, an effective SPOA will involve very significant fabrication to the steering and suspension. I'd rather trim a guard than mess with chassis welding and steering parts.

As for BL, the first car I body lifted in 1999 is still running that body lift without a problem. I'd rather lift the (relatively light) body 2" than lift the whole car 5" to achieve the same tyre fitment.

How would I build a SPOA?

I'd run rear bonz-eye springs all around. I'd run a small chassis extension, and despite some fitment issues, I think I'd still run the snake racing high steer knuckle, but I'm aware it might need machining. Shocks would be Bilstien. It wouldn't ride as well as a SPUA car, it would end up about 4" of spring lift, and I'd still have to cut the guards to run something like a 34 10.5 tyre. There would be some juggling of shock lengths, bumpstop spacing, and chassis clearance to get the right balance of ride height and droop. Caster will likely need to be addressed, along with driveshaft lengths, shock mounts, rear driveshaft angle, and potentially I'd want a panhard rod on the front and a traction bar on the rear.

The car would be clean under the axle housings, which would be cool for mud. I honestly can't think of an other advantage over a SPUA car, and there's almost no chance of engineering it in Victoria.

[Cammopricey]

Thanks steve and all the others these answers have really explained it for me makes a lot more sense now

[Gwagensteve]

Oh, and the other point is that Sierras are cheap and nasty. We're not cutting the guards on a $100K land cruiser. A Sierra with cut guards and no engineers might be hard to RWC and therefore worth very little... but a Sierra with an unengineered SPOA isn't worth anything either.

It's possible to engineer cut guards on a pre-1996 Sierra without an issue, must more easily than a SPOA. I was involved in MASSES of engineer approved body wotk to run 35's SPUA for offroad use. (stock tyres for engineering) The same engineer wouldn't even consider a SPOA regardless of tyre size or lift.

Steve.

[alien]

With NCOP / VSB14 in place now pretty much everywhere you can't engineer more than 150mm combined lift anyway, so to even dream of engineering 31s on a sierra a guard chop is your only option (but then you can't engineer 31s now either due to the diameter increase) which is silly, because people have done it in the past (like me) and passed the same test brand new cars undergo to establish their handling (lane change manoeuvre). By tightening up the rules they just encourage less people to do the right thing and get engineered. By that measure alone, you might as well just do what you want and hope you don't get caught or have a crash that requires investigation (check out Monley's sierra!).

[Gwagensteve]

That's nothing, we have a car in the vic club certed on 33 9.5's and SPOA.... in the late 90's.
Only had stock sierra wheel travel, and since the owner tried adding travel he's been stuck in a vortex of custom parts/breaking stuff etc.

Actually worked quite well when it was stock travel, but it had gears and lockers and 15X8" beadlocked rims, so it was wide and low for a SPOA car.

[vet 180]

I am not a big SPOA fan myself, however if you are going to do it I would suggest doing a YJ wrangler leaf conversion at the same time. The YJ springs work a lot better with the SPOA set up due to their length (you are looking at a 9inch longer spring in the front and 6 inch longer in the rear) and it will be a nice ride. You will also get a HUGE increase in flex due to the longer spring and due to the lift you can bump stop space and run very long shocks. The YJ springs are also .5inch wider so they don't wrap as easy.

IMO SPOA is not even worth considering unless you do the YJ spring conversion as using stock springs you will gain a lot of height, no flex and put a lot of strain on the stock springs unless it bump stopped spaced to limit up travel and strain on other steering components.

The only catch is you are locked into around 7 inches of lift then with both combined. You will have to do OTT steering upgrade and extended brake lines at the same time. But it will be a weapon and you can run 33's easy without cutting the guards though since you hate that.

When I had my sierra I was very close to pulling the trigger on a SPUA stock YJ spring set up for just a small 2.5 inch lift. I was umming and ahhing between that and an RUF.

Gwagensteve how did your friend try adding travel? What type of issue did he run into?

[fordem]

Gwagensteve wrote:

I'd run rear bonz-eye springs all around.

In order to better understand the discussion ...

I googled bonz-eye springs and got a hit on a Low Range Off Road page for a spring with reverse wrapped eyes - doesn't this go "against" the general concept, which I assume is increased lift?

[Gwagensteve]

That's the point- it reduces lift.

[Angus Martin]

Gwagensteve, why can't you engineer a guard chop on a post-1996 car?
Thanks, Angus

[greyghost]

some thing to do with an ADR, that says NO modification to the front guards and inner guards.
its about crash.
the ADR is effective from July 1995, i act remember the ADR but i think it was 61A or 69A,

[Angus Martin]

greyghost wrote:

some thing to do with an ADR, that says NO modification to the front guards and inner guards.
its about crash.
the ADR is effective from July 1995, i act remember the ADR but i think it was 61A or 69A,

Yay! Yet another Coily problem...

[alien]

Same goes with Coilys and doors - the coily doors have intrusion bars and leafys dont... you can engineer half doors on a leafy but not on a coily (because holden drovers came stock with half doors).

[Sookie]

Cammopricey wrote:

I need a bit of help understanding why spring over is so bad

Facebook tells me it's the only way you will get a Sierra to work well??

[Gwagensteve]

And turbos. Every G13 needs a turbo.

[J--A--C--K]

If not a turbo then a camshaft and high comp pistons are enough to make any sierra wheel stand

[henno]

J--A--C--K wrote:

If not a turbo then a camshaft and high comp pistons are enough to make any sierra wheel stand

An easy way to spot people who have never actually played with custom cam shaft profiles and high compression pistons is it's almost always those people talking up the benefits of custom cam shafts and high compression pistons.