Extended front radius arms

[Team Pink]

As you know I am fitting Disco 300tdi axles to my SJ based racer. I have been thinking of using the Disco front radius arms, however they are only allow, at the most 10" movement in standard form. The issue is that the bushes in axle end of the arm run out of movement and the axle tube is acting like a giant torsion bar. Without the soft bushes the axle would cycle up and down with both wheels in bump, with a single wheel in bump it would lift the opposite wheel off the ground. I experimented yesterday on a complete axle set up, there is very little movement in the bushes with even my weight on the end of the radius arm. That being said the suspension does work up to the limits mentioned above, it is simple to package and works at high speed (not something that can be said of many 3/4 link setups I see)
My question is: Will extending the radius arms, by say 30cm, improve the amount of bump travel on the axle? I am pitching at 12" on the front. If I go down this route I will use Johnny Joints (or their equivalent) at the chassis end. I am struggling a bit with the geometry, on one hand the radius arm extension will reduce the angles longitudinally however the angle the axle makes across the chassis in single wheel bump does not change and this is what the bushes limit.
Any help appreciated

Tim

[ScottieJ]

I think longer radius arms probably would help increase travel a bit.

I know of people disconnecting one bolt from one radius arm to increase articulation by reducing the effect of the axle acting as a torsion bar but that will give you some sketchy handling at speed I would imagine, what about perhaps running 2 softer bushes to allow a bit more twist? Not sure if it would work but perhaps worth a try.

As for setting up 3/4links to work at speed have a read of this thread http://www.pirate4x4.com/forum/showthread.php?t=701536" onclick="window.open(this.href);return false;

[dunk]

Hi Tim, as Scottie says above alot of ppl including me on my sj have cut one of the bushes off the radius arm so it's three link as I didn't have as much flex as I wanted with the arms complete. My sj just isn't heavy enough to get the bushes to flex. I did try drilling the bushes before I cut the arms and that did help but not enough. Rockwatt offered to make me some custom arms but I am happy with the set up at the moment. I am not sure how the cut arm would stand up to race abuse, it seems ok on mine so far but only time will tell. Some custom twister arms like the ones that rich was going to use on silver zuke might be better for you as they will help stop the axle acting as an anti roll bar.

[Team Pink]

Scottie thanks for the reply. I have a thread going on Pirate to see what info I can glean, I have my firesiut at the ready!

Radius arm disconnect does not work at speed. Drilling a hole top and bottom in the radius arm bushes does allow more flex as does fitting old (soft bushes) this will give me at most 10" bump travel.
Reason for doing this, I am looking to beat the simpler Bowlers not join them, if I copy their suspension I will be no different

[ScottieJ]

That's the spirit bowlers in the dust!

I'll dig out a few other good threads on pirate I have saved on link set up for you at lunch time.

what springs are you using? Just a normal coil set up or some proper coilovers?

[rockwatt]

Tim give me a call if you need any help :-)

[ScottieJ]

Some might be more relevant than others and you might have already found some of these but this is all the threads I'm subscribed too on front suspension geometry from when i was looking into coiling my SJ.

There is some good tech and info in these threads you've just gotta have a good read

http://www.pirate4x4.com/forum/showthread.php?t=364383" onclick="window.open(this.href);return false;
http://www.pirate4x4.com/forum/showthread.php?t=614378" onclick="window.open(this.href);return false;
http://www.pirate4x4.com/forum/showthread.php?t=307322" onclick="window.open(this.href);return false;
http://www.pirate4x4.com/forum/showthread.php?t=812155" onclick="window.open(this.href);return false;
http://www.pirate4x4.com/forum/showthread.php?t=546241" onclick="window.open(this.href);return false;
http://www.pirate4x4.com/forum/showthread.php?t=7503" onclick="window.open(this.href);return false;

[ianedwards]

I've got a disco 300 tdi engine, gearbox, transfer box, axles, think we only just done new balls on the front axle, and a winch bumper for sale if any ones interested.

Ian