Adjustable 4 link / pan hard / traction bracket

Bluesprinter

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Aug 25, 2008
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ive been trolling on google for what is "best setup" for a car with 4-link rear end and it can get pretty technical for the average joe to understand.
Plus the information is not directed towards a car like a AE86, most are based on hotrods and drag cars.

So ive been playing around with my car which has Adjustable un-even 4 link / adj pan hard / traction bracket.

Basically started with the same length or as close as possible to the stock arm links and went from there.
lowered car.
Played with pinon angle and what felt good was left alone.
lowered car about 1-2cm more.
then i started to play with the bottom arm links which now connects to TB, traction brackets, because at this current height everything was clunking and making them normal horrible rose joint noise haha

since then i have now shorten the bottom links about 1cm shorter then stock length and the rear end is now rather solid while driving straight but also slides way easy but more controllable then when it was at stock length, so basically i have shorten the wheel base of the already short wheel base car.

reason i went shorter is because i notice the springs seats on the diff was not lining up correctly to the spring location on the chassis which made the springs sit on an angle while on its own wheels, which was likely to make noises and move about while driving and basically felt like shit. now its shorter, it lines up better and the driving is better.

am i doing something right or wrong? or do i just go off by the "if it works for you then its good" approach or is there a proper way to set these things up?

i know i could bring it to a shop to get a full wheel alignment done on the car but that still wont make me understand how and why it is set to the way it is..and i know for a $170 wheel alignment fact that most places dont know shit when it comes to rear end alignment with 4 links.
 

Tim.duncan

Active Member
Nov 11, 2008
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Snowy mountains
i have no experience with this

but in my mind and from what i have heard rose jointed un equal rear is not a great idea

the rear end binds up on an 86 (one reason they are great for drifting) by adding no movement of a rose jointed bars you put all that stress on the mounting points. So maybe keep a close eye on the brackets and make sure they are not starting to pull away from the body

just an idea but maybe remove your springs and shocks put the car on jack stands and move the diff around and see if you can feel the binding at all

like i said i have no experience so sorry if im being a key board warrior.

OR go full equal rear end with the rose joints ooooo drooollllll
 

Pat

Active Member
Nov 29, 2006
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e-town tasmania
there is a good article on sam's website regarding this sort of stuff..... but to do it properly, you will need a good magnetic angle fella thingy....

actually i think there is a good article on here about it also...
 

johl

Member
May 8, 2007
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brisbane
i have heard that you keep moving the pinion angle until you just start getting axel tramp, then back it off slightly
 

Bluesprinter

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Aug 25, 2008
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Sydney
maybe one day i'll go back to half bush if i dont end up going equal length conversion.. but not a major concern for me right now

rear end needs more playing around with, im getting good and bad results with these changes im doing so far but nothing neutral that im after. i could raise the car and that would fix all the problems but why take the easy way out hey lol
 

johl

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May 8, 2007
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brisbane
is there any truth to running a half bush on the top passenger side? something to do with witch magic in the panhard rod arc of movement?
 

Bluesprinter

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Aug 25, 2008
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Sydney
only thing i can think of with using bush on the chassis side is to stop binding and twisting? like clunking noises and stuff that i'm now having LOL..
 

Pat

Active Member
Nov 29, 2006
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e-town tasmania
this stuff is all done well with sam q's articles, and im sure frak, karl et all could tell the stories bettererer than me, but they go along the lines of the old group a days the 86 guys experimented with rose joints and bush, and the fastest settings they came up with were rod ends with drilled out drivers side top bush...

there is a good thread on pf that talks about diff bind in live axle vehicles, mainly aimed at equal length rear ends, but a lot of the details are applicable to our setups also
 

Sam_Q

Member
May 26, 2006
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S.E suberbs of vic
http://s-86.com/

a great resource and a very clever fella!
not that clever, good at making people believe things though!

I had good sucess running a double rod end for my pan-hard and rod ends for diff end of the 3 main links as Dave suggested. I have poly bushes on the body end. Lowering the pivot for the lower trailing arm on the diff housing helped my traction off the line.

Also I keep mentioning it and I need to add this to my article like so many other things but people should be running rubber boots over their rod-ends. Their the equivalent of an open bearing and their in a terrible place to have something that sensative. I do beleive that boots pre-packed with some grease inside will significantly prolong the life of the joints. These are available on ebay and other places.

The reason why it's bad to have a solid bush linkage setup on the back is because of the unequal link design. With a shorter top trailing arm the diff will want to rotate under compression and vice-versa for droop. However when the car leans the bars are trying to make the diff do two completely contradictory movements. I have yet to figure out what actually gives, I suspect it's flexing the floor pan and flogging the crap out of the joints.
 

jondee86

New Member
Jul 14, 2007
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New Zealand
Trailing links "binding"...

Perhaps if you think of it this way. With unequal length trailing links, as found
in the AE86, the end of the link attached to the axle travels a shorter arc radius than
the end of the longer link. This means that there is a tendency for the axle housing
to rotate (pinion angle change) as the rear axle moves up and down.

Now consider what happens when the car leans, and one end of the axle housing
wants to be higher than the other. Each end of the axle is at a different part of its arc
of travel, and therefore, each end of the axle is trying to rotate at a different rate (by
a different number of degrees). But as the axle is rigid, rather than twist the axle
housing, the forces generated are transmitted to the trailing links.

In effect, the forces are trying to stretch or compress the trailing links. With rubber
bushings, the rubber will compress to accommodate the change in length required.
However, when the bushings are compressed, they act like a spring, and resist the
change in length. That is, they are reluctant to allow the axle housing to move to
where it wants to move. This resistance is what is known as "binding". To allow the
axle more freedom of movement, it was traditional to weaken one of the top bushings
by drilling the rubber (top link forward end where scrutineers couldn't easily pick the
modification up).

Needless to say, when the rubber bushings are replaced by sperical rod ends, the
"change in length of the links" can only be obtained by distorting the fixing brackets
or supporting bodywork. Equal length trailing links do not suffer from "binding" of
this type, as the ends of the top and bottom links have the same arc radius.

Cheers... jondee86

PS: I just made this stuff up based on common sense and what I have read :)
 

Anastasios

Member
Oct 7, 2006
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Sydney
so the ideal off the shelf setup for grip is to use traction brackets, arms with poly bushes, rubber bush on pass side top drilled out
 

Jimmee1990

Member
Apr 15, 2012
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Mount Dandenong
As long as you're not running the car very low it is okay to just use rubber bushes for the top arms. The lower from standard you go the further from ideal it becomes and a equal length 3 or 4 link will be a far better option purely for performance. On one of my uncles old race cars we used expander foam painted black as the upper body side bush on the left hand side. So even unbolted it looked like it should for scrutineering.