radius arm vs 3link

[dbeverett]

That's why im just guna copy someone elses design, using someone elses numbers, and someone elses brackets allowing adjustment

[80's_delirious]

....................... Flipped arms will also slightly increase the effective length of the radius arm IMO because it is flatter.

If it is a stock housing and a stock arm AND IF it is possible to simply flip the arm and it fits without changing castor etc then nothing changes....the spring still fixes the axle housing to chassis height and the straight line distance from chassis bush to rear axle bush is the same even with a curve in the arm....thats how my mind sees it anyway hahhaha I could be blind for all I know

the actual length of the arm wont change, I know this, BUT a std arm with 5" lift as per will be angled down a lot, shifting the diff rearward, flip the arm, it is in a much flatter position, and will place the diff very slightly further forward than a stock arm in stock orientation with same height springs.

[80's_delirious]

All I can say to that is... If the the road handling is wrong, then I dont want to be right.

But I will say, If your brave enough to cut and redo your chassi mounts back a few 100mm and get custom arms made. Thats still going to be better than what I have.

absolutely, check out Rockcrawler31's build thread, this thing has 300mm longer radius arms and flexes pretty damn good, mind you it needed a decent swaybar in the rear to get the front working fully

[uninformed]

....................... Flipped arms will also slightly increase the effective length of the radius arm IMO because it is flatter.

If it is a stock housing and a stock arm AND IF it is possible to simply flip the arm and it fits without changing castor etc then nothing changes....the spring still fixes the axle housing to chassis height and the straight line distance from chassis bush to rear axle bush is the same even with a curve in the arm....thats how my mind sees it anyway hahhaha I could be blind for all I know

the actual length of the arm wont change, I know this, BUT a std arm with 5" lift as per will be angled down a lot, shifting the diff rearward, flip the arm, it is in a much flatter position, and will place the diff very slightly further forward than a stock arm in stock orientation with same height springs.

as I havent had a good look at the nissan and toy arms I cant say for sure. But I THINK it may be a case of just looking flatter. If that distance from chassis bush to rear axle bush stays the same(set by the fixed length of the arm) and the spring stays the same I cant see it pushing the axle forward. Im thinking about a upside down trinagle the opp side (spring) is fixed length, the hyp (RA) is fixed length so the adj side must be fixed the same.....what may change is the rotation of the diff as the arm locates the axle bush mounts....

Looking at a rover front end you cant just flip the arms as the coils, with inboard shocks, are in the way...

EDIT ok what I think is happening is the housing is rotated....you 5 inch lift may put the front axle bush lower in standard location and higher in flipped location. The point of rotation is the rear axle bush as this is still the same length either way and the spring is still holding the same height. When the front end is viewed from the side I think the axle housing is rotating anti-clockwise, thus pushing it slightly (very) forward, but in reality the gemoetry has been changed bugger all...

?????

[80's_delirious]

you might be right?

will have to measure it up sometime.

[TheBigBoy]

Nope, wrong uninformed . Forget about rover. Seriously, go look at a 80 series front end. This will explain it for you... And help everyone else who is considering doing this mod themselves.

Firstly, The jig is set up as an exact replica of a standard height front geometry. Meaning all heights of axle centre, mounting axle bracket bushes, and chassi mounting bracket bush. Is all at correct factory heights and widths in relation to a stock set up.

The factory arms are set up for the correct castor at factory hieght. In this pic, the steel arms that bolts to the diff centre housing holds it at this angle.


Here is the arms bolted upto the factory brackets. Under axle centre.


As you can see the chaasi side bush lines up effortlessly in the hole makered S for stock. And each hole goes up in 0.5 of an inch to dial in caster perfectly.


Bolt in front bush infront of housing.


Bolt removed.


This is what happens with suspension height lift when bush 2 is still bolted up. Remember though the factory caster angle is still being held by the bracing arm. This is why the after market arms locate your diff forward. Otherwise it would pull the diff housing closer under the vehicle. Thats why I set mine up on a sliding scale for the correct possition nomatter what lift.


Now I have chosen the desired height lift.



Here is the differences between the 2 mounts. Although it is sitting up on the original bracket. You can see that my arms are sitting slightly back from the stock possition (Not dead center of the bushes). And after the mount where cut off it sat lower. But because I turned the brackets inwards on the housing, it made the drivers side ride up a bit on the pumkin by 10mm. So I inturn raised the other side 10mm. The difference in height between the second bush (inside of diff housing). From the underneath possition to ontop is 3" in height. Note the BIG hole you see in te pic is not the bolt hole. Its below that.


The height difference is shown here.

The difference between bush 2 and the chassi mount bush. Is about 2", if that.

Hope this helps.

[uninformed]

Big Boy, you are missing what Im saying....if you were to flip any brand arm and (were able to) mount it flipped but with the bushes in the same stock postion, it makes no difference other than maybe rotating the housing.

BUT my guess is it is pretty much impossible to JUST flip stock arms and have them mount up....new housing mounts need to be changed and this is where the difference is coming from....when you change any of the mounts (housing or chassis) you are changing geometry.

[TheBigBoy]

That was already talked about in earlier posts. If you flipped an arm that disected the axle centre point. And mounted to the same points. It would make no difference at all. But forget that... Because we are talking about landcruiser.... It doesnt disect that point and sits lower. When flipped it sits higher. So its impossible to use the same points. All your doing is confusing people with all the rover talk.

[TheBigBoy]

What I have done here isnt rocket science. Its pretty basic and easy. For everyone who says it makes no difference. They are wrong plain and simple... It drives a hell of alot nicer as the relationship between the chassi bush's and housing bushes are almost back to stock in a straight line (but note, I did the high steer and lifted panhard at the same time). It handles the small bumps a hell of a lot better. The big bumps feel the same. Driving the same road Im used too and know all the bumps that I used to try and miss I aim for now. And cant hardly feel them. Slightly more body roll. And because I turned my arms in on the housing. Wheel travel is outstanding. Especially the fact of how easy the front wants to move now in relation to the rear. Ie... People put a real heavy duty rear sway bar on to get their front to move. My stock rear sway bar has seen the front matching the rear already.

Struth will back that as he has now seen it. I will do a report and pics, when its tuned and finished and driving. Not shocks/bumstop removed etc..

[Struth]

Big boy, do you have a picture of the flipped arm in the jig at standard height, I am interested to see if the axle housing remains in the centre of the radius arm bushes or if it moves either rearward or forward of the axle centreline.

By the looks of your pics the radius arm bushes are rearward of centre when at 5" of lift.

I can now picture the axle wanting to roll anti clockwise on bumps when mounted standard and clockwise with arms flipped (looking at passenger wheel that is). Which to me will help slightly with the absorbtion of bumps. Is this why yours feels better on small bumps do you think?

[uninformed]

first of all, it has nothing to do with the disection of the axle center point....it has everything to do with maintaining or changing the STOCK mounting points, REGARDLESS of brand.

I 100% agree that what you have done has change things....you have changed the stock geometry so with a 5 inch lift it is better than what stock mounts+lift would be.

my point regarding the flipped arms, and where most of the guys here have come from, was if you just flip a RA and bolt it back up to stock mounting locations nothing changes except the look of the arm and maybe the housing roatates some(which would change castor)

Im starting to think it is not phyiscally possible to simply flip an arm.....I think that with that must go a change in housing mounts and this where the changes lie.

[TheBigBoy]

I dont have a pic of it mate. But in standard fact set. The chassi point is still above the level height of the rear housing bush. So when flipped it actually does move the housing rearward in relation to the centreline of the 2 bushes. And I definately think thats why it feels better on bumps. The arms are close to level and it wants to go up with the bumps.

[TheBigBoy]

Im starting to think it is not phyiscally possible to simply flip an arm.....I think that with that must go a change in housing mounts and this where the changes lie.

Thas exactly right. To maintain those mounting points. You have to get custom arms cut. Just by flipping the stock arms, you HAVE to make new mounts. And rotate them on the housing to keep stock +3 caster.

[rockcrawler31]

As for the question of whether it would be better to inboard the axle or chassis ends of the arms i would say that "technically" if you could only inboard it say a couple of inches and not a complete triangle then the axle end "might" nett better results. But i would hazard a guess that either end would give a decent improvement given that now the arms would prefer to start rotating around the narrowed end rather that fighting at the axle end.

And the reason that a narrowed axle end mounting points would travel more than stock has a LOT less to do with geometry/distance from arm to track width and a whole lot more to do with the original issue of bush binding. The bushes trying to move in opposing direction and twisting the axle along it's length starts from a factor of zero at the middle of the diff housing to a maximum at the wheels. I.E. the axle rotates around an imaginary point in the middle when articulating. Ergo, 3mm of bolt deflection within the bushes at the wheel might nett 10 inches of wheel travel, but with the mounts further in then that same 3mm of bolt deflection would allow a whole lot more freedom of the axle.

I think the whole arguement is a little moot though since we're talking about road going vehicles. After all, if this was a trail only vehicle built from the ground up we'd be using a double tri 4 link. since it's road going (even if we don't care about road manners) then packaging comes into play. So whatever becomes easiest to package will win. So we can sit here and have academic arguements about the minutia of the geometry (and i encourage that just so we have a better understanding of the whole thing), but at the end of the day we'll end up with what we can fit in there.

[TheBigBoy]

Not might. Does . Now along with that the arms are flipped and level also increases this point. Ill post pics when done.

[brooksy]

OK boys ... after all this insight what would be recommended for the build I am doing ??
I can have arms angled either way at chassis, but with the mounts at diff being mounted out wider & the diffs being Rockjocks I am probably only going to gain width at the chassis I guess 30-40mm/side due to turning circle but obviously having chassis mounts inboarded has no restrictions.

The build http://www.outerlimits4x4.com/viewtopic ... 3&start=60" onclick="window.open(this.href);return false;



brooksy

[Struth]

I would be angling the RAs so they are wider at the chassis and as inboard as sensibly possibly on the diff.
It just makes sense to me that having the RAs angled in at the diff end will allow more free articulation before the bushes bind and having them as close as sensibly possible at the diff will equal better wheel travel for the amount of articulation you get at the RAs.
Don't forget (and you probably already know) to put spacers between the RA bushes at the diff end and the castor plates, to again allow better articulation before the metal of the RA contacts the metal of the castor plates.

Cheers

[uninformed]

whats the trade off? angle them for more articulation but loose a bit of handling. Keep them parrallel and loose a bit of articulation and gain back your handling..

Is out and out flex the most important thingh on this truck? (probably not as you have gone with RA's) If it is a high speed truck I would think that handling win over flex.

[Struth]

whats the trade off? angle them for more articulation but loose a bit of handling. Keep them parrallel and loose a bit of articulation and gain back your handling..

Is out and out flex the most important thingh on this truck? (probably not as you have gone with RA's) If it is a high speed truck I would think that handling win over flex.

I would agree with this.

[rockcrawler31]

Personally i'd angle them inwards at the rear.

Why?

Because having them tapered in at the diff, any amount of compression of the bushes would allow bump steer and misalignment of the diff when hitting an object during driving.

Sure "technically" having them inboarded at the front would allow more movement but the trade off would be the locating of the diff housing.

I can tell you that my way has been proven to work with Chad's "the professor" hilux. That thing had rear tapered RA front and it was able to use the entirety of the hydraulic front coilovers travel.

In the end it starts to get the same principles as a torque tube single link set up as seen in Mogs. I.E. the axle and arms start rotating around the rear mounts AS WELL AS the front.

[rockcrawler31]

whats the trade off? angle them for more articulation but loose a bit of handling. Keep them parrallel and loose a bit of articulation and gain back your handling..

Is out and out flex the most important thingh on this truck? (probably not as you have gone with RA's) If it is a high speed truck I would think that handling win over flex.

I agree to an extent, BUT there's a proviso

a LOT of teams in speed events and even the U4 boys will customise their sway bar set up to suit each individual race or stage. Personally if i hadn't gone with a 100 series spring swaybar, and gone a standard currie swaybar, it would be a very quick job to select a higher rate bar for a speed event. I mean it's literally a 10 minute job to swap out bars.

So it's very easy to have say a double tri front and rear suspension that flexes like a mofo with no sway bars for crawling stages, then finish your stage, chuck in a high rate sway bar and do the creek run with full control over the car.

MILO

[brooksy]

Moving the RA's in at diff is just not going to happen as centre won't allow it among other things.
As in my first reply in this thread (I think ) my original intention was to have the chassis mounts in about 30mm/side but after some good discussion here I thought I might throw my build into the mix.
The reason is mainly due to my scenario I won't be having much uptravel (approx 3-4") but plenty of down travel (running 14" coilovers). My thoughts are based the same as Milo & also the wider the mounts at housing giving better speed control & factoring in the increased down travel combined with wider mounting at housing giving a wider arc at flex on droop side which can only help limit/reduce binding.
Yeah Struth I had intended on running chassis end brackets with 5mm spacers each side just to help with the increased down travel & also running 80 series bushes at chassis end too as they have better bushing flex than Patrol.


brooksy

[TheBigBoy]

I didnt know what to expect when building mine. I have another housing ready just incase. Im giving you the feedback. Its made stuff all different with the only noticable thing, slightly more body roll. No wondering or wobbles... Im having trouble finding shock long enough to warrant the build.

Im actually wondering if its too much travel. Makes for good photos though.

[Struth]

I didnt know what to expect when building mine. I have another housing ready just incase. But all this talk about trade off by moving the radius arm mounts inwrad by 30mm. Im giving you the feedback. Its made stuff all different with the only noticable thing, slightly more body roll. No wondering or wobbles... Im having trouble finding shock long enough to warrant the build.

Im actually wondering if its too much travel. Makes for good photos though.

I run 6" lifted 80 series rear shocks in front of mine, but have cutom shock tower height and custom pin mounts on the diff, they allow for the shock to not bottom out on full compression and use it's total travel downward. You can get plenty of flex out of 80s arms. As well both my RAs are more inboard than normal for 80s arms but parrellel.

[TheBigBoy]

Shock stroke is around 300mm. I have a set available to me at 325 eye to eye. But even that wont be enough to use is full potensial. Ofcourse thats with custom shock towers. Youve seen the pics struth. And how effortlessly the front wants to flex.

[uninformed]

Rockcrawler, good info mate, thanks

Brooksy, you know to take all my posts with a dose of salts....just ideas, not real experience.

Im trying to visualise why you need the spacer for down travel? I can see how on cross axle flex the rotation of RA's can hit againt the brackets they are held within, but if straight up/down movent, is it not the chassis end and panhard that will bind

[rockcrawler31]

Rockcrawler, good info mate, thanks

Brooksy, you know to take all my posts with a dose of salts....just ideas, not real experience.

Im trying to visualise why you need the spacer for down travel? I can see how on cross axle flex the rotation of RA's can hit againt the brackets they are held within, but if straight up/down movent, is it not the chassis end and panhard that will bind

It's all good mate, sometimes a fresh set of eyes on an old arguement or subject is as important as a bunch of dude's who have been debating the same shit for 4 pages

As for the down travel thing, the way i read it is Brooksy is still talking about cross axle articulation but on the downwards component.

[brooksy]

All good Serg. Spacers are for chassis end.
It is for cross flex where on droop the wheel naturally wants to fold under towards opposite wheel.
A standard panhard would bind at axle end but running a heim or bushing with bolt running perpendicular to axle & on horizontal plane so binding eliminated as indicated in pics in the build thread.


brooksy

[Struth]

Shock stroke is around 300mm. I have a set available to me at 325 eye to eye. But even that wont be enough to use is full potensial. Ofcourse thats with custom shock towers. Youve seen the pics struth. And how effortlessly the front wants to flex.

Yep the pics show grouse flex. My shocks are just over 300 mm travel too.

[TheBigBoy]

Shock stroke is around 300mm. I have a set available to me at 325 eye to eye. But even that wont be enough to use is full potensial. Ofcourse thats with custom shock towers. Youve seen the pics struth. And how effortlessly the front wants to flex.

Yep the pics show grouse flex. My shocks are just over 300 mm travel too.

Ha ha, its friday, go enjoy a SLAB of beer.

Ps. Who makes bigger remote resevoir strong shocks. Im still keen on the amada's but alot of fabing to get them right in the front. Whats the point of all this flex if you cant use it.