Radius arm flex

[Struth]

Which radius arms will flex better,

80 series type or Rover type i.e ones with an eye on the chassis end of the arm or ones with a pin?

Are there any disadvantages to one or the other?

Also if it would fit size wise would a Rangie rear top link (A frame) be a good idea in a 4 Runner coil rear.

Application will be a coil SAS 4 Runner chassis.

Cheers

[bazzle]

With a pin as they can rotate without straining the diff mounts as much .
BUT with a lot of drop they will still bind the bushes.

BAzzle

[JOHNZ]

80 series are better

[Slunnie]

80 series are better

For what technical reason?

[joeblow]

they all have thier merrits but most of the time they are not set up correctly.

[Struth]

they all have thier merrits but most of the time they are not set up correctly.

What are the merits of the rover arms over the 80 series or vice versa?

I need to make a choice on which arms to use, I already have the 80s arms but will get hold of some rover arms if they are more suitable for a weekend warrior that is intended to play pretty hard.

Cheers

[oondy]

It comes down to the distance between the bush centres at the diff end - patrols are 240mm from memory, where as toyotas and rovers are both 160mm (i think - with out measuring). This gives both these cars decent flex in the front for a stock setup. The rover arms however are somewhat longer than the cruiser arms so they get a greater angle between the arms before the bushes are at their limit.

cheers

OONDY

[KiwiBacon]

If you want more flex, simply shift the radius arms inboard more.

[Struth]

It comes down to the distance between the bush centres at the diff end - patrols are 240mm from memory, where as toyotas and rovers are both 160mm (i think - with out measuring). This gives both these cars decent flex in the front for a stock setup. The rover arms however are somewhat longer than the cruiser arms so they get a greater angle between the arms before the bushes are at their limit.

cheers

OONDY

Goodo, the 80 arms are about as long as I can go otherwise I will run into the trans crossmember where they mount to the chassis (I think, need to cut IFS off and position axle to determine this first.)

I know where there are a couple of sets of Rover arms at a wreckers so will measure these first, also check how they mount to the diff which I think is different to the 80s which mount under or on top of and the Rover mount to the rear of the axle housing.

Cheers

[Struth]

If you want more flex, simply shift the radius arms inboard more.

This is relevant to what the engineer will let me get away with. ATM it's the guage of the chassis that is seting this, which is fairly close together for a 60 series diff and already quite close to the diff pumpkin on the driver side.

Cheers

[ISUZUROVER]

Rover radius arm:

[Struth]

Rover radius arm:

So under or on top of the housing as well.

Cheers

[ISUZUROVER]

So under or on top of the housing as well.

Cheers

Under.

[dumbdunce]

the rover/bundera type will work better at standard suspension heights. the further they are lifted without correcting the pin to eye angle at the chassis, the more they are bound at rest. the 80 series type are "easier" to lift and easier to achieve good ramp scores, since you can just loosen the bolts and let them pivot freely. the axial rotation available from the 80 chassis end bushes is sufficient for more flex than most spring/shock setups will allow.

as has already been mentioned, the distance between the axle end bushes also plays a significant role - the closer together they are, the less compliance required in those bushes to alloy a difference in angle between left and right. for this reason the 80 and rover are better than the patrol.

if you've opted for a system that is like any of these, articulation is probably not your primary concern - it is a system inherently set up for stability and control.

[Struth]

the rover/bundera type will work better at standard suspension heights. the further they are lifted without correcting the pin to eye angle at the chassis, the more they are bound at rest. the 80 series type are "easier" to lift and easier to achieve good ramp scores, since you can just loosen the bolts and let them pivot freely. the axial rotation available from the 80 chassis end bushes is sufficient for more flex than most spring/shock setups will allow.

as has already been mentioned, the distance between the axle end bushes also plays a significant role - the closer together they are, the less compliance required in those bushes to alloy a difference in angle between left and right. for this reason the 80 and rover are better than the patrol.

if you've opted for a system that is like any of these, articulation is probably not your primary concern - it is a system inherently set up for stability and control.

You are correct the system is to improve dramatically over the IFS and retain stability on road, but the question of which type of arms is important because when I take it offroad I am looking for challenging tracks that will require winching as well so therefore good articulation will be a big plus for such tracks.

The angle of the pin style arm at the chassis mount is easily overcome as this will be manufactured to suit the radius arm angle when at rest, the lift will be built in with the SAS and hopefully will not need to change.

So basically I have a solid coil sprung front with the arms as close together as possible and the ability to manufacture the chassis mounts to suit the radius arm angle when at rest, my thoughts are that the Rover arm will offer better flex (we are not talking wild up and down travel, but improved up and down over say an 80).

Is there any advantage to the Rover arm over the 80 arm in this scenario?

Cheers

[dumbdunce]

So basically I have a solid coil sprung front with the arms as close together as possible and the ability to manufacture the chassis mounts to suit the radius arm angle when at rest, my thoughts are that the Rover arm will offer better flex (we are not talking wild up and down travel, but improved up and down over say an 80).

Is there any advantage to the Rover arm over the 80 arm in this scenario?

Cheers

not really. you can gain a small offroad (ramp, really) articulation advantage by loosening the bots on the 80 style arms at any time and they will allow to tune your height settings.

all other things being equal, the best flex will be achieved from the most compliant axle end bushes at the smallest spacing. so depending on whether 80 or rover have the axle end bushes closer together.

plus what you can get your hands on cheap is what it usually comes down to

[Struth]

So basically I have a solid coil sprung front with the arms as close together as possible and the ability to manufacture the chassis mounts to suit the radius arm angle when at rest, my thoughts are that the Rover arm will offer better flex (we are not talking wild up and down travel, but improved up and down over say an 80).

Is there any advantage to the Rover arm over the 80 arm in this scenario?

Cheers

not really. you can gain a small offroad (ramp, really) articulation advantage by loosening the bots on the 80 style arms at any time and they will allow to tune your height settings.

all other things being equal, the best flex will be achieved from the most compliant axle end bushes at the smallest spacing. so depending on whether 80 or rover have the axle end bushes closer together.

plus what you can get your hands on cheap is what it usually comes down to

Well I have the 80 series arms, so that's pretty cheap really

Thanks for the input

[dumbdunce]

Well I have the 80 series arms, so that's pretty cheap really

Thanks for the input

makes for an easy decision

[Slunnie]

It may be worth looking at the Disco2 arms then.

I tend to think these flex better than the Disco1 arms as the axle bushes are bigger, though as Serg and I compared measurements we found that the bolt spacing was also larger to accomodate the bush. The Chassis end is bolted through so ride height is irrelevant. The arms will twist in their mounts like any link bush.

This is what I would be looking for and mounting them to the chassis will be very straight forward. In the pic the uppers are fronts and the lowers are rears.

[Struth]

The Disco front is very close to the 80 front, so would stick with the 80 series I think.

Cheers

[greenslinky]

If you are after more flex in the 80'series radius arms,fit GU patrol bushes,they have holes in the bushes and if you press them in so the holes are vertical,they will compress more under load.The front bushes work more on vertical compression than twist.The rear bush does twist.I would flip your arms if possible,depending on your lift ,keeps the arms parallel with the chassis,better for clearance and road driving etc.I wouldn't recommend triangulating the arms with a front diff,it will cause you problems on road.Moving the arms in eqal distance ,closer to the centre of the diff will improve your articulation .Hope this helps,regards Andrew

[uninformed]

If you are after more flex in the 80'series radius arms,fit GU patrol bushes,they have holes in the bushes and if you press them in so the holes are vertical,they will compress more under load.The front bushes work more on vertical compression than twist.The rear bush does twist.I would flip your arms if possible,depending on your lift ,keeps the arms parallel with the chassis,better for clearance and road driving etc.I wouldn't recommend triangulating the arms with a front diff,it will cause you problems on road.Moving the arms in eqal distance ,closer to the centre of the diff will improve your articulation .Hope this helps,regards Andrew

why would mounting the arms on top make it handle better on road???

if your talking about front axle roll axis, and whether it has roll understeer or roll oversteer, isnt it the center of axle line to center of chassis mount that determines the angle of roll axis?

the reason i say axle center line is because if you run a straight line from the front radius arm axle bush to the rear radius arm axle bush on a rover it goes through the axle center line.....


Serg

[greenslinky]

I agree with your roll axis,but when you increase your susspension height,you need to correct the castor on the axis.eg castor offset bushes,castor plates,drop boxes.All the above correct castor for under or oversteer but the drop boxes improve bump steer as well ,that's what i ment about on road handling.Having the arms hanging down at a larger angle increases bump steer shock,that is why drop boxes work well,the radius arm angle,castor,roll axis is returned to standard.Flipping the arms on top of the diff if set up right with castor should have the same effect.I prefer wheel articulation and clearance.In a perfect world you would would raise steering and panhard points to reduce bump steer also.By the way i'm not an expert in the field ,just love building trucks.

[uninformed]

I agree with your roll axis,but when you increase your susspension height,you need to correct the castor on the axis.eg castor offset bushes,castor plates,drop boxes.All the above correct castor for under or oversteer but the drop boxes improve bump steer as well ,that's what i ment about on road handling.Having the arms hanging down at a larger angle increases bump steer shock,that is why drop boxes work well,the radius arm angle,castor,roll axis is returned to standard.Flipping the arms on top of the diff if set up right with castor should have the same effect.I prefer wheel articulation and clearance.In a perfect world you would would raise steering and panhard points to reduce bump steer also.By the way i'm not an expert in the field ,just love building trucks.

i understand what you are saying, but if the front axle is rasied "x" and the chassis mount stays the same, i would have thought this is the 2 important factors.....drop boxes work because the lower the chassis end and return the axle center line to chassis mount angle, but flipping a arm doesnt change the axle/chassis relationship..... it may improve bump steer as the arms are closer to level, but not much......

what am i missing????

Serg

[KiwiBacon]

i understand what you are saying, but if the front axle is rasied "x" and the chassis mount stays the same, i would have thought this is the 2 important factors.....drop boxes work because the lower the chassis end and return the axle center line to chassis mount angle, but flipping a arm doesnt change the axle/chassis relationship..... it may improve bump steer as the arms are closer to level, but not much......

what am i missing????

Serg

I agree with Serg on this one.
The angle or even shape of the arm doesn't matter, it's the relationship between the two things it's holding apart.
Radius arm ontop or underneath doesn't change that.

[1MadEngineer]

http://www.outerlimits4x4.com/ftopic170370-60.php

ahhh memories...

[Struth]

http://www.outerlimits4x4.com/ftopic170370-60.php

ahhh memories...

Yes I thought of that thread too

[ISUZUROVER]

Great diagram Struth:

[Struth]

Great diagram Struth:

Excel is your friend

[greenslinky]

Hi Struth,forgive my ignorance but i can't see why you need to locate the front radius arm bolt/bush in a direct line through the axle to the chassis mount.Flipping the arms on top with new brackets set to re-align castor seems to work.I know it doesn't get away from the fact that you still have the same axle chassis relationship if you used the same front locating points inverted or not.But if the front reference point is raised so the axle is no longer the centre ,shouldn't this give you a new axle chassis relationship(like the opposite of a drop box instead on top of your diff).Aren't you achieving a similar concept to drop boxes just with heaps more work? Cheers Andrew. P.S. pics are really good.