[Gwagensteve]

I had a few minutes today to knock up a little CAD sketch of how radius arms work to demonstrate the problem.

It's not to scale and none of the angles are specific, but nonetheless, it's indicative of what happens when a radius arm suspension is in use.



The blue radius arms represents the car at rest and at ride height.

If the suspension is merely compressed and extended without any articulation, the relationship between the bolts won't change at all,

However, if the suspension is flexed, you can see what happens to the axle end of the arm -

The black arm represents full compression and the red arm full droop. In each case, the bolts have moved completely to the edge of the bush hole in the arm. In the case of this drawing, I put 15˚ between both arms, equally 7.5˚ up and down. It doesn't matter what the ratios are though - whenever you're trying to flex a radius suspension, the same thing is happening. If those bushes are spherical bearings that don't permit any vertical misalignment, then there can't be any flex without the axle housing twisting or the arms bending.

This is an exaggerated example, but it's exactly what happens when a radius arm flexes. The resistance to compressing these bushes is where the high roll stiffness comes from in a radius arm design, and it's why urethane caster correction bushes (and in fact, caster correction bushes of all types) increase roll stiffness and therefore reduce flex. It's also why removing one axle bolt removes ALL the roll stiffness in a radius arm suspension, and why cars with urethane bushes (which don't generally compress as easily) break their axle brackets off.

I hope that makes sense.

Steve.

[monley]

They do allow for a little bit of vertical misalignment, just not as just as you would get from stock bushes and it takes quite a bit of force to compress the rubber that holds the joint in place.

I think patrol bushes would be the go in jimny arms

[JrZook]

monley wrote:

Good for leaf springs to

http://www.lowrangeoffroad.com/builderp ... ounts.html

Would work in a leaf spring as the spring does twist. May even relieve some torsional stresses in the main leaf.

[Paulw]

monley wrote:

I was also going to run these in my jimny when I had it as my middle bush keep tearing and was going to replace with a johnny joint but only the middle link. I think It might of even been Steve that suggested it to...

How about if I kept the middle bush as a johnny joint and swapped the Johnny joint from the front diff spot to the chassis end and put a OEM rubber bush in the front diff end?
Or would that be bad?

[Gwagensteve]

You'll have approximately half the flex of a standard jimny.

Steve.

[greyghost]

this is why tube radius arms disappeared off the market about ten years ago, when APIO and D&G tuning started to have massive and dangerous failures with the arms. they quickly removed them from sale, but some "bright spark" said tube is cool and stronger, so we'll make these so our jimmy's can be hard-core. and you all fell for it.

a jimny gets most of its flex (in the front at least) from the arm twisting along its length, hence why almost all radius arms are I-beam's. they have to be for a radius arm to work without too much "binding", strengthen the arm so that it does not twist and the bushes are the limiting factor then you flex your junk and tear the mounts off the diff.
you could get a tube radius arm to work but you'll need rubber bushes that are about 200mm in diameter (so they have room to flex), but that's just stupid.

as for the OP, the spherical bearings will not promote flex, just your mall cruising ability, and not even doing that very well either.

[alien]

I know thread is a silly idea, but ... could you fabricate some sort of threaded center section to the tube to allow it to physically twist?

[Gwagensteve]

That's been tried. Better to make the mount to the axle tube able to rotate to remove roll stiffness.

[alien]

so if you could somehow mount those whacky bearings on the previous page around the axle tube, then bolt the diff mount to that you'd have an ideal solid mounted setup? Surely there would still be vibrational issues.

[3cyl]

Wonder what ever happened to the setup that replaced the front bush on both radius arms with a crossover link that mounted to the housing in the middle? It was called a "crosslink" or something. Only ever saw it in a photo once, must have involved chopping off the front part of the mount on the axle tube and the crossover link was supposed to control torque and pivot on the axle tube to allow articulation.

[31zook]

^X-link if you are going looking for it.

[SierraDan]

http://www.dobbinengineering.com/0463ed ... 77c87.html

[got_bar_work]

All that force on a weld the size of a coin on a peice of sheet metal sounds like a bad idea to me

[SierraDan]

Haha what?

[got_bar_work]

The x link design
The install video i have seen was just a 30mm pin welded on the housing
No double plating
No bracing
Not even double sheer

[Jezza86]

greyghost wrote:

this is why tube radius arms disappeared off the market about ten years ago, when APIO and D&G tuning started to have massive and dangerous failures with the arms. they quickly removed them from sale, but some "bright spark" said tube is cool and stronger, so we'll make these so our jimmy's can be hard-core. and you all fell for it.

a jimny gets most of its flex (in the front at least) from the arm twisting along its length, hence why almost all radius arms are I-beam's. they have to be for a radius arm to work without too much "binding", strengthen the arm so that it does not twist and the bushes are the limiting factor then you flex your junk and tear the mounts off the diff.
you could get a tube radius arm to work but you'll need rubber bushes that are about 200mm in diameter (so they have room to flex), but that's just stupid.

as for the OP, the spherical bearings will not promote flex, just your mall cruising ability, and not even doing that very well either.

have there been any reports of failed radius arms in the jimys? aftermarket or other?

i disagree that the JB rad arms are limiting. i have them and am not running a swaybar and i know for a fact that the shocks are limiting. and after that the spring falling out (or spring retainers) are limiting further flex. the bushes just keep going and the bolt sleve binds and there's plenty of other components preventing this.

the majority is limited by their sway bar.

[zukenutter]

The only tube arms that I've heard of failing was Bugsta's but they were a one of, locally made set.

[BertZook]

plus they failed after a rollover

[zukenutter]

BertZook wrote:

plus they failed after a FEW rollovers

and a floggin', but that's old news.

[Paulw]

Same I haven't heard of any JB ones failing but have seen pics of OEM ones bent.

I've ordered from Amayama some stock rubber bushes for the diff end, I'm gunna try flexing it up using a mates engine hoist and do some measurements tomorrow (will also take my old arms and test with them as well with all poly bushes) then when the new bushes arrive I will try it with them in the front with the johnny joint on the chassis end and will also try the arms out with all oem bushes as well. Wonder if I could borrow some stock arms with oem bushes from someone in SA to test out for comparison as well?

[Gwagensteve]

I wouldn't continue to flex the car with the jonny joints in the axle end. The force on the axlehousing and axle brackets will be pretty scary. Jimnys already bend their front housings as they flex- these bushes jugs make it all the worse.

Steve.

[Paulw]

wouldn't it be the same with the superpro bushes?

[Gwagensteve]

No, that's the whole point of the thread. The stupidpro bushes are bad, but they allow some deflection.
When Suzuki designed the car, the bushes would have still had some deflection left at full flex (limited by the shocks) so axle and bracket loads are low. Add longer shocks and springs or fit tighter bushes, and the axle is what's trying to give.

[sideways]

No.

The jonny joints don't offer any deflection, the only way you're getting flex now is by bending things. I wouldn't drive the car until you replace them with rubber or poly because sooner or later, you will break something.

There is absolutely 0 advantage to flex by running those joints in the diff end, be it just one with a rubber in the other spot or in both. They might make the car drive nicer but that's because they're restricting the housings ability to move around. I'd certainly give them a shot in the chassis end though.

At the other of the scale, bushes made out of bubblegum would offer fantastic flex but drive like crap, it's all part of the compromise.

Edit, beaten again.

[Paulw]

ok the bushes are coming out and putting the old arms back in for now till the new rubber bushes shows up.
Thanks for the advice.

[greyghost]

Jezza86 wrote:

have there been any reports of failed radius arms in the jimys? aftermarket or other?

i disagree that the JB rad arms are limiting. i have them and am not running a swaybar and i know for a fact that the shocks are limiting. and after that the spring falling out (or spring retainers) are limiting further flex. the bushes just keep going and the bolt sleve binds and there's plenty of other components preventing this.

the majority is limited by their sway bar.

if you read my post this original idea was over TEN years ago, the Malaysian Jimny guys has several fail and the pics were all over the net at the time. they were using the red APIO arms, this caused APIO to pull there arms off the market.
they were failing where the rear diff mound was pulling off the arm, so the diff was able to rotate around the front mount. bending the steering, pan hard and ripping out the brake lines.
the tube wasn't failing just the mount.
D&G were trailing there jimny in the German trials series and had the same failures before removing there arms from the market.

the best designed aftermarket arms on sale at the moment are (I hate to say it) is the Snake racing arms, as these retain the I beam design.

[atari4x4]

Pretty sure Sheps ORA arms are plate rather than toobe.

[Jezza86]

greyghost wrote:

if you read my post this original idea was over TEN years ago, the Malaysian Jimny guys has several fail and the pics were all over the net at the time. they were using the red APIO arms, this caused APIO to pull there arms off the market.
they were failing where the rear diff mound was pulling off the arm, so the diff was able to rotate around the front mount. bending the steering, pan hard and ripping out the brake lines.
the tube wasn't failing just the mount.
D&G were trailing there jimny in the German trials series and had the same failures before removing there arms from the market.

the best designed aftermarket arms on sale at the moment are (I hate to say it) is the Snake racing arms, as these retain the I beam design.

yes i read your post, did you read mine, or steves?,

unless you've removed the front swaybar and completely reworked the front suspension with coilovers, its not going to happen.
the bushes dont bind the way your saying, because they are soft and allow the angles involved with 1-3" of lift. and I can say that's a fact, because i have a jimny, with longer shocks that only just hold my 3" lift springs in place.

with one wheel tucked and the other airborne, there is still free give in the bushes and front arms because if i undid this shock the left wheel would drop, and the spring fall out, and then, as the axle drops, the mounts or arm itself become the next (and last thing) providing any roll stiffness in the front. in which case, then they become exposed to the damaged you are suggesting.


and here's sheps ora arms

[alien]

Would you get better movement by having a pin at the end instead?

[Jezza86]

what you actually need to get flex from this set-up front arms that have lower controll of the castor angle, via larger, softer bushes, or lower arms that only attach to one mount, and a third upper arm to controll the castor.

cannot remember what thats called.. 1+1+1 link? something like that