[sideways]

I agree with MrRocky that this is all a bit academic and pointless for a fun weekender on 30s. It's worth noting that virtually every coil sprung 4WD suffers from excessive front roll stiffness and a floppy rear end but that doesn't stop everyone from having a good time and going places in their horribly setup Patrols/80 series/rovers that lift front wheels 2 feet into the air when they run over a pebble on a hill climb.

Aside from Jeeps, all the mainstream coil solid axle 4WDs in Australia run radius arm front ends but unlike a coily they run 5 link or A frame 3 link rears which have no inherent roll stiffness making it very difficult to get good balance. The coily (sans sway bar) is kind of in front here, but it only does that by having having high roll stiffness (thus bugger all articulation) in both ends. Is no flex better than horribly unbalanced flex? Meh.

Jimny front coil towers are available new from Suzuki for somewhat reasonable prices. Although it would be easy to engineer (Jimny has near enough same weight/chassis width/diff width/spring rate/dampening) the Jimny front towers have the shock mount built into them and it's very low. In a Jimny you're limited to approximately an 8" travel shock without bump stop spacing. If I was going to all that effort and cost, I'd want to be able to fit longer shocks (and thus have more potential for flex) than that. Can the radius arms provide enough flex for more than 8" shock travel? Probably not, but it leaves headroom and if you're going to do mods like this then it might as well give more benefit than just greater off the shelf parts availability. I'd look at vitara rear coil towers in the front and Solid axle Hilux or TF rodeo front shock towers which will allow much longer shocks. It's not any more work but it gets you a more flexible result, you don't have to use the extra shock length. It saves you doing everything again if you decide to 3 link +panhard later on.

If I was building a coily for hardcore offroad use (which I wouldn't, I think they're for people who want the fun and feel of a stock/mildly modified Sierra) I wouldn't do anything special to the rear end, just the usual springs and longer shocks. Find whatever spring gives the longest free length for the desired ride height with out reaching coil bind (consider custom ones) and shocks to match. Plate the diff mounts before they break. 3link + panhard the front end with the above mentioned coil/shock towers. If possible find some lower links from the rear of some heavier vehicle that are the right length (for ease of engineering) and the top link from one of the 5 link rear wagons. Utilize the standard front radius arm chassis mounts and add your own for the rest. This will get you no front roll stiffness aside from what is provided by the springs. Rusho had this done to his coily and it was engineered. 31zook did it to his Jimny and the results were very impressive.

At the end of the day I think you'l have more fun with just a basic <2" lift. Spending $$$$ and dozens of hours researching and modifying to get better balance offroad is going to be pretty tedious and the money would sure be more fun if it was put into the fuel tank or a G16b and the time used getting out there and driving the thing. Then it doesn't need engineering either, passing the pits is just a spring and/or tyre swap away. Even Josh (31zook) said that his wasn't really all that much more capable with the 3 link anyway.

Does anyone know how far apart the diff end radius arm bushes are and their diameter? From this we can compare to other radius arms. The numbers on Jimny arms would be interesting also.

[got_bar_work]

I wonder if bruce could make softer diff bushes. U cant go to soft or it would move around to much under power /brakes

[Gwagensteve]

epitam wrote:

I did it... search israeli coily on readers rides.

Sent from my SM-G900F using Tapatalk

I think you sort of did the opposite - lowering the spring mount and attaching it to the axle whilst raising the lower shock mount. I agree it allowed a longer spring to be fitted, but it isn't clear how close to the factory bumpstops you can now get when the suspension is fully compressed, so how much total travel has been increased isn't clear.

Obviously, you now have some complicated clearance problems, some of which are due to the new lower spring mount, some related to the lower roll centre the 4X4art kit introduces.

[Gwagensteve]

I hope this thread has helped someone learn that you can make small changes to the rest height of a coil sierra, and without revision of mounts and custom fabrication, that's about all.

The thread moved towards a discussion of how to reduce the limitations inherent in a coil sierra suspension, and whilst it's interesting insofar as it can teach us what those limitations are, very, very few people will ever seek to do anything about it because of the reluctance to cut up their cars.

That's fine - I wasn't advocating anyone chopping into their coil sierra. What I was advocating is to be very wary of lift kits for SJ80's, the myth of "long travel" and the idea that adding lift increases travel or has positive effects on suspension behaviour.

I think (hope?) this thread has done that.

Broadly, I hope it encourages people to reduce lift height and therefore have cars that work as well as possible.

I'm still pretty interested to hear about Discos's proposed radius arm design though.

[vet 180]

Good thread.

[DiscoS]

It has been awesome reading all the new info guys, and I 100% agree, a weekend off-road weapon just needs 30's and balls (BYO).

So now I'm going to try and hijack all this good thinking, into thinking what I want for my vehicle specifically.

I have no major complaints with my vehicle off-road. I owned a bone-stock SJ80 for years and I, and everyone around me, was always impressed with what it could achieve. Now I've got a 1.6, 30's, and significantly greater driver skill, after lockers, and maybe getting some fancy trailing arms fabricated (very long term there), I can't think of anything else I'll do. This thread has helped cement my belief that I don't really need to do much for my off-road ability, but my on-road ability is just disappointing. I have to take speed bumps slower than a Mazda 3 because I'd like to be able to use my spine in the future, I corner like a hummer, and brake like something that doesn't like to brake in a straight line.

I like about 1.5" of lift, 225/75R16, and that's it.

I don't understand the negativity around bumpstop spacing, it has it's place, and when one goes from 26' to 30" wheels, 2" of bump stop spacing is NECESSARY. (I'm aware that 225/75R16's are 29.5", but let's just keep the numbers nice and easy)
This would net me about 10" of travel, which is huge, and even factoring limited aftermarket quality, 8" is still a 33% increase in travel. (And also more than enough for me)

Questions:
What shock absorber (front) can even do this?
Best brand to get custom one made? (if any can do this)
Best brand to buy off the shelf and modify? (somebody mentioned they had seen somebody do this with Koni's, any more info on that?)
Can the terrible stock front-top shock mounts handle this much flex, or will it just break the mount?

[Gwagensteve]

DiscoS wrote:

I corner like a hummer

You'd be doing very, very well then. If you'd driven a Hummer (as in an M998 HMMWV or H1 Civilian Hummer) you wouldn't make that comment. They'd outcorner quite lot of road cars. My Dad owned one for a few years. They're very balanced, have incredible turn in and are very car-like to drive....anyway,

Quote:

I don't understand the negativity around bumpstop spacing, it has it's place, and when one goes from 26' to 30" wheels, 2" of bump stop spacing is NECESSARY. (I'm aware that 225/75R16's are 29.5", but let's just keep the numbers nice and easy)
This would net me about 10" of travel, which is huge, and even factoring limited aftermarket quality, 8" is still a 33% increase in travel. (And also more than enough for me)

I'm certainly not negative about bumpstop spacing at all. The problem is this:

Quote:

Questions:
What shock absorber (front) can even do this?

There isn't a shock with 10" of travel that meets the other criteria - it has to be very small diameter, so most likely, it's going to be a monotube shock. These also have heavier walls which will permit welding the coil seat in place. As I've explained though, monotube shocks aren't travel efficient, so you won't get 10" of travel. You might find your 2" bumpstop spacing nets you very little increased travel at all.

But lets assume you can get 10" of travel. you're going to have to design a very trick spring to deliver 1.5" of lift but keep the spring tight at full droop. It's going to be incredibly low in rate, which will make for a very strange car to drive. Note that cars running 10" coilover shocks use hugely tall spring stacks with up to three different rates and adjustable top platforms to tune ride and ride height, and you'll be trying to achieve that with one spring with one rate. (Yes, there are variable rate springs, but most feedback is that these cause some odd effects on a road car because shock valving is determined by spring rate, so the car will be over or under damped depending on which bit of the spring you're riding on.

Quote:

Best brand to buy off the shelf and modify? (somebody mentioned they had seen somebody do this with Koni's, any more info on that?)

GT suspension in Flemington set up a coiler with custom valved Koni's with spring seats welded on. They were very expensive back in 2000 when it was done, and the engineer who did it (Josh Browne) has since retired I think. The car rode great at speed but was fairly firm at low speed.

Quote:

Can the terrible stock front-top shock mounts handle this much flex, or will it just break the mount?

It's not flex that breaks them, it's shock rate and age. The real problem is that as you add travel the shocks will have to try and bend around the coil mount section of the mount - because the coils are very small diameter and there's very little space for the shock.

If you want to try to significantly add travel, swap in Jimny shock and coil mounts and sidestep all the problems. IT's the cheapest sensible solution.

Steve.

[epitam]

Gwagensteve wrote:

epitam wrote:

I did it... search israeli coily on readers rides.

Sent from my SM-G900F using Tapatalk

I think you sort of did the opposite - lowering the spring mount and attaching it to the axle whilst raising the lower shock mount. I agree it allowed a longer spring to be fitted, but it isn't clear how close to the factory bumpstops you can now get when the suspension is fully compressed, so how much total travel has been increased isn't clear.

Obviously, you now have some complicated clearance problems, some of which are due to the new lower spring mount, some related to the lower roll centre the 4X4art kit introduces.

Well,
I like to see you are updated... Nut before i installed the forart kit i had mad custom set , that i drove for around 2years happily.
Made out of:
Front - falicia mid 90' spring (which was very soft and long, an narrow, around 46cm, almost long as the forart 4" spring but still set lower)
I've haded a anti roll for the front to handle better on road
Rear - lwb vitara rear springs, which was good for my extra weight on the back.

Shocks were koni, rear made for samurai and the front are koni made for vitara 2" lifted (twin tube,40mm tube, 29cm closed 47cm opened) and welded carefully .

The only thing i should have done ... Is took the radius arms and the penhards from the for art and it would be perfect... But i wasnt so smart back then and installed the whole kit with the penhards brackets .... And lately change the springs to softer ones (jimny bits 3") still..... My older setup works the best. Comfort wise in road and off road and much better when flexing on rock crawling....

And here are some pics from the process:
https://goo.gl/photos/f8zkZaHJc4XjmgkdA

This is my old seup....





















This is the forart 4" kit ( which i already changed quite a bit to rubber bushing on the axle mount, and high steer and others)

Comparison front forart spring and the falicia....

[DiscoS]

That is an awesome sway bar man, could you share some info on that?
Is it all custom, is the tube stock, is the arm aftermarket?


Looking at the stock Jimny setup, I feel very uncomfortable with this and the SJ80's top shock mount system, I just don't like how they're dealing with angular movement of the shock (bushes).




This is a blown stock SJ80 mount. In my mind I feel like this is inevitable for any shock using this top mount position, it also seems like the SJ80's mount is much higher, and I don't feel like losing travel.



In that last photo, you can see the hole where the top of the sock pokes through the body panel, and it's stock mounting position.

Would it be possible to fabricate something like this?



Which would allow a double-eye shock to be fitted like this:



Most likely the side panel there is incapable of dealing with these stresses, but it shouldn't be too hard to modify the stock shock tower to be able to fit a double-eye shock. And there's already a hole in the engine bay there, and nice little things to cover them, I don't see why I wouldn't be trying to retain all of the possible length I can.

I'd want ultimately something like this:



Or this:



Ending up with something like this:
https://www.tntcustoms.com/jeep_parts/j ... er_bracket



Thoughts?


EDIT:
@GSteve
I see no reason why I couldn't fit these:


And having the springs losing contact at full droop is genuinely least of my concerns, heaps of people have this issue with no effect on 99.999% of their driving time

[Gwagensteve]

epitam wrote:

This photograph reinforces my point. That spring will bind long before the axle contacts the bumpstop. The compressed length of the spring is too long. With large (circa 2.5") bumpstop spacers this will work quite well, assuming that's what you want.

Quote:

looking at the stock Jimny setup, I feel very uncomfortable with this and the SJ80's top shock mount system, I just don't like how they're dealing with angular movement of the shock (bushes).

Most 4WD's run a pin top shock mount. In fact, it's easier to name the ones that don't than the ones that do. The pin will bend before the mount. Double shear mounts are only required or a coilover shock where that bolt is supporting the weight of the car, not just shock force. Packaging a double shear mount on the front of a sierra is very hard if you don't want the tyres to hit the mount.

Sure you can run sliders and tender springs. (and that photo you posted is confusing and I suspect from a road car coilover) On an actual coilover. You don't have that so there's nothing for the slider to slide on. If you fit the style of slider to run a fully compressed tender spring it will make the compressed length of the spring pack huge - you'll end up with no compression travel. If you want a tender spring, you need an actual coilover so the slider can actually slide on the top of the shock body. I you want a 10" travel coilover, you'll find the compressed length of the shock is prohibitive.

A 10" emulsion coil over is 17" long fully compressed. that's going to be well up inside your inner guard. It needs lots of room to move and space for the springs. They're very invasive. and all its going to do is highlight the limitations of your radius arms and burn a circa $2K hole in your pocket once tuned and sprung.

Springs that go loose on full droop make a car unpredictable when flexed up and on a big angle. It's one of the other reasons I limited my rear travel to keep the springs tight. This is especially true if it's also hard to get the compressed side if the axle to settle onto the bumpstop - the end result is a very unstable car.

Steve.

[Joe]

I got lost trying to read this thread

The bushes in my coily look a bit cruddy and need replacing
Car is my daily and will pretty much be used on the beach and some bush work too so not after super duper mad flex or anything.
Will this kit be ok?
http://www.ebay.com.au/itm/Full-Suspens ... SwBw5XRVEO

Now for my next silly question Does this kit do front and rear or front or rear? I've had a really long day and i've been reading the add for a hour now and i still don't know if i'm reading right

[got_bar_work]

It looks like its both. Just be aware that greg is not open till feb. Hes moving from sydney to Newcastle.

[Kor3y101]

It looks like it is front AND rear Joe,
The ad says it comes with rear diff bushes and caster correction bushes.
I could be wrong though but it appears that way to me. I would think so for that price also!

[Joe]

Cheers fellas

got_bar_work wrote:

Just be aware that greg is not open till feb. Hes moving from sydney to Newcastle.

Most places are closed for a bit at this time of year anyways