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BigJimnyMeet (North) 2024 (12 Jan 2024)


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Jimny 4 Link Suspension

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24 Aug 2020 06:34 #227246 by Busta
Replied by Busta on topic Jimny 4 Link Suspension

Roger Fairclough wrote: Iv'e never liked polybushes and your photos prove the point.A standard void type bush does not extend past the radius arm so the arm can twist and it's this twist that allows the suspension to work in articulation mode. Look at the photo and you will see that the flange on the polybush is stopping this flex.
I would suggest you replace the polybushes with original void bushes and then you will see full articulation.

Roger


Dave used to tell me off for saying poly bushes don't flex, and indeed his super Jimny clad with 900kg of accessories did flex very well, but i agree with you. The standard bushes are thoughtfully designed. Poly bushes and castor correction bushes both seem to bind up and limit flex.

Still, I would be interested to know of any simple ways to get more flex from the standard setup. Changing to a 4 link setup seems too involved.
I'm sure someone used to sell a kit where one of the bushes on each axle was on a little linkage, so it could move up and down a couple of inches relative to the radius arm.

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24 Aug 2020 06:49 - 24 Aug 2020 06:50 #227249 by Lambert
Replied by Lambert on topic Jimny 4 Link Suspension
Would not using fabricated arms but with rose joint ends at the chassis allow for a better flex without going mad?

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
ADOS Attention Deficit Ooooh Shiny!
Last edit: 24 Aug 2020 06:50 by Lambert.

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24 Aug 2020 06:58 #227250 by zukebob
Replied by zukebob on topic Jimny 4 Link Suspension
If I remember correctly, Zapnologica has the 4xFourart radius arms. My understanding is that they have Johnny Joints at the chassis end. If we can talk him into testing rubber bushes at the axle, we would know.

I started out with nothing & still have most of it left

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24 Aug 2020 07:15 #227251 by Zapnologica
Replied by Zapnologica on topic Jimny 4 Link Suspension
So to me this is all a very controversial topic.

I installed my 4xfourart 100mm lift kit not know much about suspension, and going on peoples advice. I have had some issues with it along the way, and had all sorts of comments & opinions from people. Ranging from its my sway bar, to the bushes are binding, coils, shocks, steering etc etc. So I have taken it apon my self to practically test everything that everyone says, to see if its applicable to my ride and how it works in the rear physics world. I have really enjoyed this and learnt a whole lot in the process.

Here is my thoughts:

Bushes:
Stock rubber bushes are very good and flex well, they however do start getting very stressed when flexing on the extreme side. It will wear them out quicker and start tearing. They are also much better resistance to sand / mud as they are sealed unit. I have often removed my various polly bushes to find sand & gunk inside them not ideal at all.

I do tend to agree with @rogders comment about how the polly bushes fill up the entire gap and prevent the radial arm from rotating. I have been through a few sets of polly bushes. I currently have the softest most squishy bushes I can find. And they do flex very well.



Old on the left and new on the right (red)

Old was a solid poly compound way to hard in my opinion, however its shape wouldn't resist rotating as much. The red bush is a hollow honey comb structure and much softer, however its quite square on the outside.

That said I do have rose Joints on the chassis side of the Radial arm, which should also alow the whole arm to twist if need be.
Im gonna do a write up this week of my findings of stock vs poly bushes, with some videos comparing each.

But @ Rodger I would like to challenge / ask more info your comment regarding the radial arm twisting?

From my tests when the suspension was binding on full flex, the bushes where not trying to twist left to right, but where wanting to move up and down. When I removed that rear castor bolt and flexed it again, I gained tremendous amount of flex, and the radial arm did not look like it wanted to twist at all (at this stage it was being held by a rose joint at the chassis side, and one soft polly bush on the diff side. It could have twisted if it wanted to, (how much it could twist is a different story).

So I went old-school and got out some cardboard and drew up this small 2D simulation of the suspension:


What this demonstrated to me was why the rear polly bush wanted to pull down. The two blue lines are the diff angels when fully compressed vs fully drooped. Top one is compressed (so Right hand side radial arm in my test) and the bottom line is the LHS radial arm. This explains the binding to me perfectly, because 4 bushes simply cannot counter such a big angle is difference. (this is what got me onto a 4 link idea, ad the axel line will stay level throughout the compression stage?

What I am stugaaling to understand is this TWIST in the radail arm that you speak of. From my very limited suspension theory, and my simple 2d drawing. this issue is actually not that the diff wants to move, but as the radail arm drops it goes through its radail and the bottom bush starts dropping, the more you want to droop, the greater that angle?

In my head and from my little cardboard drawing a 3/4 link is the only setup that will not cause that vertical binding. (this is in the theoretical word) Again I'm not saying all the effort,cost & complexity would be worth those extra few inches of travel.

Crazy Idea:

For those on a budget, I theories that this could be a cheap and rather effective solution. Not to sure how one would do it. But if you could SLOT the radial arm mounting on ONE of the front and ONE Of the rear axels. It would Give quite a bit more flex. Maybe build some sort of a bracket I dono.

Something like this:


Its a crap Idea, I know. Just thought I would share it.

2015 Suzuki Jimny

4" 100mm Lift
M18A Motor
Crawler Gears
Dual Air Lockers
Lots of mods.
Attachments:

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24 Aug 2020 07:19 - 24 Aug 2020 07:20 #227252 by Zapnologica
Replied by Zapnologica on topic Jimny 4 Link Suspension
I have videos comparing both, But difficult to post here. I will try to put them on my blog and do a bit of explaining.

But long and short. Jonny / rose joint on chassis side (flexes more & less resistance and will do so 1000 times with no worry), Rubber does twist but resists when you twist it far. It also strains the bush. (however Jonny Joint is more maintenance)

On the diff end, I don't think you can get better than a stock Suzuki Jimny bush.

But I do not believe the bushes are what limits you, Its the geometry of the radial arm setup. The bushes are just acting as some play towards making the geometry less Ridgid.

2015 Suzuki Jimny

4" 100mm Lift
M18A Motor
Crawler Gears
Dual Air Lockers
Lots of mods.
Last edit: 24 Aug 2020 07:20 by Zapnologica.

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24 Aug 2020 07:56 #227255 by zukebob
Replied by zukebob on topic Jimny 4 Link Suspension
Suspension mods, especially discussing more complex mods, is an intriguing subject. Sometimes that causes the discussion to become a little spirited but don't let that deter you from posting ideas. If anyone goes too far just tell them to pound sand.

I started out with nothing & still have most of it left

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24 Aug 2020 07:58 - 24 Aug 2020 07:59 #227256 by zukebob
Replied by zukebob on topic Jimny 4 Link Suspension
That said, your slot won't work. :evil:

I started out with nothing & still have most of it left
Last edit: 24 Aug 2020 07:59 by zukebob.

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24 Aug 2020 09:10 #227262 by Roger Fairclough
I don't like polybushes and I don't like rose joints, at least in a road car and we need to consider that point carefully. Is the end result meant as a road car with the ability to go that much further along that track or do you want something that will climb Ben Nevis with ease. I was the GLASS rep. for Warwickshire and I organised green lane runs all over and one day this guy turned up with a tray backed Hi-lux on big fat tyres. It was hopeless. The back end was so light it skipped about and on wet grass it was lethal. Think carefully about your ultimate aims and remember that you should not attempt to emulate the abilities of a guy who has spent a fortune to get the very best and is determined to show everyone how to do it.
Going back to rose joints and my apparent dislike of them is based on the fact that they are for competition use. Yes they are wonderful at controlling movement and giving you flex aplenty but on muddy or sandy tracks wear will be prodigious and vibration will be unpleasant. Noise vibration and harshness (NVH) is a major concern to a car maker and chunks of metal bolted underneath a motor is proof that to combat NVH needs must.
We all start out with a motor that is better than us and hopefully we progress to being better than the motor. At that point we should have accrued enough knowledge to know what to do next.

Roger

ps I agree with zukebob, the slot won't work, it would tear itself to pieces.

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24 Aug 2020 09:43 #227264 by Busta
Replied by Busta on topic Jimny 4 Link Suspension
The best analogy for understanding how the suspension moves is this: Hold a stick horizontally in front of you in both hands. The stick is the axle. Your arms are the radius arms. Grip tightly and move one arm up and the other down, as if the axle was articulating. You should feel resistance as the broomstick tries to twist in an opposite direction in each hand. It is this twisting movement that causes the radius arms to bind up.

Years ago Rhino Ray produced radius arms with a pivot at the chassis end to supposedly allow more flex but it never really caught on. I don't believe this is the plane of movement that is causing a restriction.

Here's one example of modified radius arms that aim to allow more twist at the axle end of the arm:

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