[Gwagensteve]

I've had an feeling about this for a while but I was outside playing around with Piggles and a Bobcat today so I was able to prove it.

Commodore rear shocks are TOO LONG for the front of a sierra with 2" Bumpstop spacing.

My setup is OME front springs, 100mm shackles, stock 1.0 shock mounts, stock 1.3 spring plates and 50mm RHS bumpstop spacers.

I cut the hoods off my commodore shocks when I installed them because they were snagging my bumpstop brackets. My axle is 30mm forward with redrilled spring plates. This will have no bearing on shock length.

Here's the flex I'm getting from the front end - quite impressive for front leaves in the front



but here is the problem:



That shock is hard compressed. That's not healthy for the shock or the mount.

I'll admit my mounts have been fine - they haven't split as yet, but the shocks are pretty shagged. It's not visible in the photo, but the axle is still sitting on the bumpstop even though the axle is relocated forwards a bit. The bumpstop is heavily compressed and distorted, but that's what you'd expect.

Anyway, I've made this claim for a while but here it is in photos.

I threw these shocks in when I built the car because I didn't have any stock shocks available and wanted a cheap solution, but I've always claimed they weren't a good option. I'll stand by that.

Steve.

[stockman]

When you say too long, you mean in length not travel?

Whats the simple solution? Raise the uppermount?

[tanshi]

also it depends on which commodore shock your looking at as the sedan vs wagon are different lengths

[shep]

interesting. what brand shocks are they? i have KYB VS wagon (tow pack) jobbies with 25mm bumpstop extension
and i think it works fine.

might cut mine and have a look.

[shep]

mine are too short however

[Gwagensteve]

Too long when compressed.

It's very difficult to check unless you have the hoods cut off. It's also hard to anticipate what the measurements will be when you are compressed hard.

There should still be some shock shaft showing (ideally about 1") in that photo.

Yes, raising the top mount is the answer, but if you are fabricating mounts, why not do it properly, lift the shock off the spring plate so it's out of the way and can't get damaged by axlewrap and fit a decent shock rather than a pissy car shock?



Here's an N76 mounted on top of the axle at full stretch.

Steve.

[royce]

I dont think anyone thats isnt just respurting half an idea of what they read has ever claimed them to be a perfect option

What brand are they? some have a longer compressed length than others its been noticed which will cause troubles

FWIW when I came across them as an option all those years ago (same time the whole redrill for RUF thing popped up strangely enough, was a bit of a dodgy day I used Genuine Holden shocks, which were more than short enough to compress properly with no spacer

[Gwagensteve]

I don't remember - they are Gabriel wagon rears I think.

It was a few years ago when I bought them and I didn't care much when I did. - I just needed some shocks quick and knew they were going to go in with 2" bumpstop spacing to clear 34's.

When I pull them out I'll see what part # is on them before I throw them in the bin.

Steve.

[tanshi]

i use a celica shock on the front of the LJ,

the commodore shocks i had were 3 inches longer than i could use any way, and i had a heap of front end flex.

its all about measuring and researching the correct length shock for what you need,

[JrZook]

Mr Gman.

I thought you out of all people would have measured the shock lengths as well as added in some compensation for bump-stop compression and found out they would have been too long in the first place.

This is like a playschool tech edition from you

[Gwagensteve]

Silly me for believing what I read on a forum

I really wasn't fussed about the suspension on Piggles at all when I got it on the road - I was always convinced it was going to coil it at some stage so it was all about minimal investment. It was all just bootyfabbed together. It ran stock sierra rear shocks with 2" bumpstop spacing (4" of wheel travel - fawk yeah!) for about three years.

You'll note the rear shock placement is perfect



Shame about the springs though.

(In fairness, as per the link school thread, with all the radius arm bolts in the rear springs don't go loose)

Interesting factoid - flexed like this, there's 5 degrees of chassis twist in my car.

[JrZook]

Gwagensteve wrote:

Interesting factoid - flexed like this, there's 5 degrees of chassis twist in my car.

Lol whats your track width? If its around 1500 that 5 degrees will account to ~3.5' extra effective wheel-travel across diagonal wheels

[Gwagensteve]

I assume you mean 3.5" not feet

Unimogs have 17.5 degrees of engineered into the chassis. Makes it a nightmare to built trays for them as they have to mount in three points only. Makes me suspicious about the bus bodies you see on them.

My favourite photo of chassis twist was of Rick Pewe's flatfender tyre testing Boggers in Truckhaven Hills, CA, when Boggers came out - It was in Fourwheeler magazine (maybe 1994?)

anyway, it was fully flexed, and the grille was angled one way and the roll bar the other.

Steve.

[SierraDan]

I found my axle hit the bumpstops a fair bit before the shock fully compressed. 30mm bump extensions and 31's.

[Gwagensteve]

It's worth remembering that if you add droop (longer shackles, opened up spring clamps, springs with more free arch) then the compressed wheel will come up higher, so the compressed length available for the shock is reduced.

Therefore a compressed shock length that works with, say, stock shocks and springs won't necessarily work with a different combination - even though to get more droop you need a longer shock extended, you also need a shock that's shorter compressed - impossible, so it's time for custom mounts.

This is only the case on the front. on the rear, it's the opposite effect because the shocks are inboard of the bumpstops.

Steve.

[royce]

How do you measure the twist in teh chassis?

For the tray, the offroad camper guys use a pretty nifty looking set of tray mounts that are sprung, so as the chassis twists it pulls and pushes on the springs

[Gwagensteve]

royce wrote:

How do you measure the twist in teh chassis?

Angle finder on front and rear crossmember. Front said 15 degrees, Rear said 20.

Steve.

[shakes]

Gwagensteve wrote:

royce wrote:

How do you measure the twist in teh chassis?

Angle finder on front and rear crossmember. Front said 15 degrees, Rear said 20.

Steve.

what is it not twisted up?

[Gwagensteve]

As in bent when not flexed? Don't think so, but anything is possible. Judging by the fit of the bull bar etc, I'd say no.

Steve

[e36pig]

so what shock is good to run on the front ? and or rear ?

[LAY80N]

I will have a look what brand shocks i have sitting downstairs. The shocks i threw on my brothers zook for a cheap fix were different lengths (slightly) than some others that people have posted up. His came close to bottoming out, but still had a bit of shaft showing at full flex. Depending on the brand and recomended fitment their seems to be a few differences.


Layto....

[e36pig]

commo & hiace gabrial shock's for 2 inch lift... so are these what i should be running with 2inch lift and 5inch shackles to get mass flex ?

[e36pig]

bump ?

[atari4x4]

3 minutes between a post & a bump... are you for real?

I don't often say this.... but FFS search noob

[e36pig]

thanks for your help .. thought it would have been an automerged post being within 10 mins ..

[JrZook]

Errrrrrr wtf mate?

[zooky08]

e36pig wrote:

5inch shackles

[e36pig]

maybe samller or bigger... just a guess.a mate made them for me and they are much bigger than stock ones.. the reason im asking about the shocks is because the shakles wont fit because the shocks i have now dont extend enough to fit them ... wondering if the commo & hiace gabrial shock's for 2 inch lift will allow for these to fit

[shep]

e36pig wrote:

maybe samller or bigger... just a guess.a mate made them for me and they are much bigger than stock ones.. the reason im asking about the shocks is because the shakles wont fit because the shocks i have now dont extend enough to fit them ... wondering if the commo & hiace gabrial shock's for 2 inch lift will allow for these to fit

firstly remove your shocks then get the ruler out of your school bag and
measure the compressed and extended distance between the top and bottom shock mounts.

get back to us with the measurements in mm.

[JrZook]

shep wrote:

firstly remove your shocks then get the ruler out of your school bag and
measure the compressed and extended distance between the top and bottom shock mounts.

Go to supercheap/autobahn with the measurements in mm.

And find a shock to suit. When sizing shocks the most critical measurement is the compressed length. If the compressed length is too long you with have to put bump-stop spacers in or move the shock mounts to suit it or both. Otherwise you will most likely destroy the shock and its mount.