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Need some Rover Radius Arm advice

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I'm at the stage in my build where I sort the front suspension

I'm working with standard front arms in pretty much standard geometry, I've spent alot of time searching for the information without any joy

What are the limits of this system and are there any tweeks to gain a bit more over standard

Realistically how much flex / articulation can you get.... or more to the point what is the biggest travel shock that is worthwhile mounting?

The way I see it the flex of the bushes will limit the articulation more than anything.... are there certain brands of bushes that are better than others?

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I started with a standard RRC in the 1993, got it going as a trialer in 95', comped it and then in 2005 made it into a winch challenge truck. All the time I've stuck with standard suspension height, because it is so much more reliable than increasing the shock length. What I'm seeing on my 72' is that on full drop, it's all pretty much on the limit of what rubber can do. I'm considering doing the equivalent on cranked arms on the back because it does sit a bit higher than normal and the bushes are at a queer angle. So that's kind of why there isn't a common lift-limit on forums, because standard is well on the way to being maxed out.

But a 2" is normally acceptable if all the bushes and king-pins are right.

The flex isn't coming from the shocks, as much as it is driven by the bushes, as you say. Really the only fix is a third top link. Once the bushes on the axel end of the radius arms cannot bind up it will be a lot better. You would get way better performance off road with a third link than longer shocks. (you could spend a long time fannying around with spring lengths and ratings)

The last few years I put diff locks in and now drive it around on three wheels. I'm not even sure you need suspension with them fitted? They fix all the articulation issues in one hit.

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An easy way to get more flex from the bushes is to drill 2 large holes, above and below the connecting bolt. That made a big difference on my Defender, but of course the drilled bushes wear out quickly.

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Thanks for that.... my suspension is being added in so lift length is irrelevant, my plan was to set the arms up so the bushes are at neutral at ride height, will rotate the axle mounts to correct caster so won't need caster correction bushes

I think from memory the shocks that were in the parts truck were 8 1/2" stroke so that would mean a 10" travel shock would be about all thats worth fitting in there if a +2" lift is as far as its worth pushing them

Was thinking the same thing Escape...don't know how legal it would be lol

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From what I've come to understand from hours of trolling the net about all you can expect out of the front end with standard geometry is about 11"-12" shock. The standard ones are 8" I think the ones I have in the Rangy are 11.5" and advertised as +5" Shocks. I assume its +2.5" up travel and +2.5" Down travel?

what are your radius arms off? The narrower early ones are better for articulation and move a bit more freely..

I have some OME 2751 +2" springs front springs at home they are 200lb/inch.

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There's some more tech i wasn't aware of.... are you referring to narrower radius arms or to the bushing at the axle end? and what models if you can remember....

Lol remember your old parts truck, the disco.... thats them, I have another set from wingnut also disco, but they have caster bushes in them and i wanted standard bushes so i grabed yours

12" is alot more than I expected the bind in the axle as it hangs under my truck (with no springs) is enough that I can lift one wheel and the other side lifts well before I've moved it a couple of inches lol it just doesn't want to flex!

I imagine the rubber bushing will be rather hard after sitting for all that time, I expect it will soften with use (I hope so lol)

I'll get a set of wheel scales and work out my spring rate first lol do things properly.... but if they are up for grabs I might grab em

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If a disco, it will be the wider arms.

Best mod you can do is keep rubber bushes, and as above drill the bushes at the axle end, 12 and 6 o'clock, 8mm drill is likely to be enough.

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Its the bush at the axle end, the earlier ones were 38mm wide and were solid rubber, the newer were 45mm wide and have an extra metal ring in the middle of the rubber. Not sure when they changed but on the Range Rover I think it was bout 1985. Mine is an 88 and certainly has the wide bushes.

So if you have stolen the ones off my Disco lol then they are sure to be the stiff as a board new wide type :-(

Yeah they wont flex much just picking up a wheel bushes are stiff as a steel girder... Drill the bushes :-)

Have a read.. http://www.pirate4x4.com/forum/land-rover/61187-holey-bushes.html

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If you look in Lewis' returning to the fold thread in members vehicles section you will see some pics of my 90 with plus 5 shocks and Lewis' own with longer shocks still.

The standard setup with some 2" longer shocks is very capeable for most if not all track and field driving.

Will.

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Very good thread, heres some of the points from it

Taken from a post by "strangerover" (for those that don't know a very reliable source....)

"in standard mounts the arm will bottom out into the axle mounts at 10.8" but was able to gain another inch or so of flex" so this backs up Ian (east..) and muddy of max 12" from pic's on the thread it was obvious that engineering modifications would be needed as the inner sleeve of the bush had bottomed out on the outter sleeve and the upper arm (when articulated) had bound the front of the radius arm up into the top of the axle mounting

Drilling holes may extend the life of the bush when used hard offroad, as this removes the area that starts delaminating from the extreme movement of articulation.... the compression of the bush till the rubber is forced (cut) out of the way when the inner sleeve trys to contact the outer, this then allows the rubber to pull away from the outer when stretched (articulated) the other way .... this does make sense

It does increase body roll... but doesn't seem to affect braking

They were using a hand drill at high speed 2-3000 rpm and drilling out to 12mm top and bottom of the bush and both styles of bush seemed to benefit from it.... the later bush with the extra steel sleeve needed a bit of a hole ground in the middle ring to center the drill

There was comments about a special bush being cast with windows to allow the sleeves room to move without cutting the rubber of the bush, but as of yet I've not been able to find any more info if I do I'll post it here lol hardly surprising given that thread is dated 2002

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I remember reading the drilled bushings threads a few years after they began, I think they even had some voided bushes prototyped, but I seem to remember the final consensus was that they did affect braking or not so much braking as allowing the axle to rotate and the longevity was poor.

Scrap Iron sold poly bushes that had a small void in them, just checked, 'Polybush' still list them.

As a loaded camper van I'd of thought you need to stay away from drilling bushes etc.

It's a bit late now, but I think lengthening the radius arms has become the thing to do now, at least to get +5 damper travel.

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There was comments about a special bush being cast with windows to allow the sleeves room to move without cutting the rubber of the bush, but as of yet I've not been able to find any more info if I do I'll post it here lol hardly surprising given that thread is dated 2002

They are not in production anymore. The voided polybush ones SOA 93 mentioned are from poly bush in the UK they are on this link. Ref 1AG

http://www.polybush.co.uk/shop/view/14_Series_I/1_Kit_2_-_Land_Rover_Defender_(90110_-_1994_to_2001)

This guy fitted them to his Disco 1.

http://www.pirate4x4.com/forum/land-rover/1368426-analyze-my-set-up-want-more-flex-2.html

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That's the other one mentioned in there isn't it - move the axle radius arm mounts closer together on one side.

It's not in that linked thread - but that chap from Pirate called Buck ran his 90 like that years ago and worked well it seems.

Not sure if that would be allowed in your build over in NZ though ?

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LOL that second thread was a read... classic Pirate, there is some good tech in there but there is also a good amount of bs, I've got a resumble understanding of suspension and I was having to put an effort in to work out the good from the bad (2hrs to sort through all the post)

A couple of points to add from that thread

Spring rate will have an impact on the performance of radius arms lol personally I expected this, the bush bind on the front has to be over come by the springs.... I'm not going to bother stating a specifics, as this will be different in different vehicles.... I will add that based on a good portion of the BS in that thread, if you have gas charged shocks they will add to the spring rate as one poster pointed out his shocks took 60kg of force to compress 1"

There was a very good post by "Bush65" that explains spring rate I've taken the liberty to copy it (sorry about the black line thing Pirate has a black background and it has copied this with out an option to change)

So here is my 2 cents worth on the question; does spring rate affect articulation?

For an example and using theoretical numbers selected so mental arithmetic is simple.

Assume static load per spring is 1200 lbf, or 2400 lbf total sprung weight acting on the axle.

Assume also the static ride height of the springs is 13" and there is 6" of bump/up travel and 6" of droop/down travel (limited by shockie length), all measured at the spring.

Application low speed crawling, and no radius arms to compromise articulation, or add roll stiffness to make calcs more difficult.

Try 4 different spring rates:
120 lbf/in (guess too light)
200 lbf/in (guess maybe a little light)
300 lbf/in (guess maybe on the heavy side)
400 lbf/in (guess too heavy)

Now the static deflection from free length is:
1200 lbf / 120 lbf/in = 10" (for the 1st spring)
1200 lbf / 200 lbf/in = 6" (2nd spring)
1200 lbf / 300 lbf/in = 4" (3rd spring)
1200 ibf / 400 lbf/in = 3" (4th spring)

Then the free lengths are:
13" + 10" = 23" (1st)
13" + 6" = 19" (2nd)
13" + 4" = 17" (3rd)
13" + 3" = 16" (4th)

Find the spring force when the 1st spring is compressed by the 6" of bump travel.

spring force = (6" x 120 lbf/in) + 1200 lbf = 1920 lbf

Now the total weight on the axle is 2400 lbf, so the spring force on the drooped side = 2400 lbf - 1920 lbf = 480 lbf.

Find how far the droop side spring has extended:
extension = (1200 lbf - 480 lbf) / 120 lbf/in = 6"

So the 120 lbf/in spring rate has not prevented full articulation.

We can do the same exercise for the 2nd spring:

spring force = (6" x 200 lbf/in) + 1200 lbf = 2400 lbf

Now this spring is carrying the total weight of 2400 lbf so the spring force at the drooped side = 0 lbf

So this spring extends (1200 lbf - 0 lbf) / 200 lbf/in = 6"

So the 120 lbf/in spring rate has not prevented full articulation.

2 out of 2 for Buck

It is obvious that for the heavier springs the method needs to be changed slightly.

How far is the 3rd spring compressed from static ride height when it carries the total weight of 2400 lbf:

compression = (2400 lbf - 1200 lbf) / 300 lbf/in = 4"

but it needs to compress 6" for maximum articulation.

it is also obvious the the drooped spring extends 4" when the spring force is zero, but that doesn't stop droop, which will still reach the 6" limit, but the spring has unseated 2".

So the 300 lbf/in spring rate has not enabled full articulation in this case - remember this is slow speed crawling, if there is dynamic load then the spring force can exceed 2400 lbf.

I won't bother calculating the case for the 400 lbf/in spring, it should be obvious now that it will only compress 3".

My answer to the question posed is that spring rate can affect articulation.



If we look at something said in the OP, that articulation was better with the 2" RTE lift than with the 3" RTE lift (or something to that affect.

What happens if we lower the ride height from 13" to 12" in the above examples. The bump travel becomes 5" and the droop becomes 7".

Then the 1st and 2nd springs would hit the bump stop before the spring force reached 2400 lbf.

But while the 3rd and 4th springs still compress 4" and 3" respectively, they are able to get closer to full articulation. IMHO that is a likely reason why the OP had better articulation with the 2" lift.

There were several good points about bush options

The slotted bushes made a very noticeable difference in pictures to the articulation, the poster was impressed with the performance off road, but with noticeably more body roll on road, but nothing he was unhappy with same with brake performance.... no comment on durability as the thread was dates mid to late last yr

A personal note from the pic's it looks to me to have allowed the suspension to balance out between front and rear better

There was a unsupported post stating that "superpro" bushes were softer and a good option but the link in the post ran to an ebay search without any specifics

Another comment was that the Nissan Patrol radius arm bushes were a better quality, I have used these in the past in suspension links (they are in the rear bottom links for my toy SIII) and they flex incredibly well.... I will have a measure up on fitting these as they maybe a good compromise

There was a post by "Bill" warning of the rotation of the axle under braking and possible axle tramp in extreme braking but he posed an interesting solution mount the shocks either side of the axle, a standard trick to minimize the rocking motion under tramp (this isn't really part of this thread subject but some thing I will consider for my truck)

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Ander, legally in NZ we can pretty much bolt anything on that doesn't detrimentally effect handling (or improve performance to a level beyond a 8 or 10% threshold) we have a 6 monthly warrent check for mechanical safety that is sposed to include a drive by the mechanic to pick up handling issues not found while under the vehicle... not hard to find places that don't bother with this

If you want to modify a vehicles performance, handling or safety systems you have to get a cert.... there are rules on what is allowed and not (the folder with these rules is close to 4" thick lol)... since the cert system is managed by mechanics they get very concerned if welding to cast items is done, it could be done and made legal but it would be easier for me to fabricate my own arm lol... but I may machine them within reason, why the Nissan Patrol bushes caught my eye

Just a note on the bushes and legality.... the drilled option would be hard to made legal a cast void on the other hand is a constant replacement wise so easier to be made legal

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In terms of cert you dont really gain anything by using standard disco/rangy bits since you are starting with a series chassis do you? Obviously there are reasons to use standard ish bits though.

I have been thinking of a vapor project, ex arm or stage one V8, even a 109 would probably be ok to start with as well, 3 link front 4 link or A frame rear with 80 serries axles and coil overs. 3.9 block with the stroker crank I have.... easy 5.2L and as far as I can tell should be cert able. There doesnt seem to be a whole lot of info floating around on what sort of suspension joints are ok to use on the road here though

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Yeah thats hard going that thread (as most are on Pirate!) I ended up just looking at the pictures lol....

Whats the diameter of the Safari bushes?? Would be good if the radius arms could be machined to fit those.

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Right... as a distraction in the shed I climbed under the toy SIII and grabbed some measurements (please note these have all been taken from bushes that are installed so there is a margin of error lol)

First here is the Rover Disco bush dimensions

Dia of outside of the bush 50.8mm

Width of bush 44.0mm

Width of pin sleeve 54.0mm

Nissan Patrol

Dia of bush 60.0mm

Width of bush 41.0mm

Width of pin sleeve 50mm

Now just because I could I measured up one of Wingnuts arm to see how much meat would be left if they were machined to fit hehe

Remember the arms are cast so the profile tapers in from the edge to a roughly 1/3 section in the middle that is level

Right the outside edge at its narrowest would still have 6mm of meat tapering out to 9mm thick for the center 1/3

Lol now I'm happy with that amount of steel, question is do I do it.... after all I really only want 10" worth of shock travel, so I stay balanced with the back... and try and keep road manors for towing

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I presume you have the arms with the wide bushes? I suggest using genuine narrow bushes, with an ordinary m16 washer either side. This is what I run, front and rear, and i am very happy with the flex and the cornering. The whole void thing is a bit lost on me to be honest; your max flex is still determined by the inner bush touching the outer, and the narrow bush is much better in this respect already.

Daan

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Daan

What are your thoughts on using the narrow with a narrow bush in a widearm axle. Some spacers might be needed either side ?

Morten

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I think that's what the M16 washer are for.

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I think that's what the M16 washer are for.

You answered the question already!

I use a wide bush axle, and narrow radius arms, with narrow bushes and a spacer at the chassis end also.

titanium bolts

You could use wide arms with narrow bushes, just be a bit carefull with pressing them in at the right height.

Daan

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