Castor Correction

Post by JK » Tue Jun 03, 2003 12:41 pm

I have done some sums and I come up with completely different castor correction figures for GQ radius arms than the normally quoted 5 - 8 deg for a 6 - 8" lift and the old 1 deg per 1" lift.

My figures indicate the following:

For every 1" lift you need 1.8deg correction
For a 6" lift you need and 11deg correction to be equivalent to stock level radius arms.

I am a little confused by the large discrepancy.

Is anyone able to explain how the after-market guys calculate the required correction and indeed the actual castor correction provided by the plates???

Post by **Wendle** » Tue Jun 03, 2003 1:12 pm

JK, give me the exact measurement from where the radius arm passes through the chassis mount to the axle centreline.
And the height from the ground to the same point on the chassis (radius arm pin center) and from the ground to the axle centreline.
I'll draw it up so the castor change for x amount of lift is in black and white.

Post by **ozy1** » Tue Jun 03, 2003 5:33 pm

i was just going to add a post similar to this, as my GQ gets a fairly large shakeup, i have a 6 inch lif, and i am aiming to get rid of this problem.

Post by **big red** » Tue Jun 03, 2003 8:09 pm

i dont think caster correction is the way to fix the wobbles as the main problem seems to be the angle of the radius arms.
i dont have the problem any more since i changed to the radius arm drop brackets and i get better downward travel as well.
some 5 links get the wobbles when the arms are on a large angle.
the wizard bolt on one seems pretty good as the angles are low.
just my opinion.......shane

Post by **hypo** » Tue Jun 03, 2003 10:03 pm

i thought the wobble came from the abgle the draglink and panhard bars where at wen they get lifted ?? or am i thinkin bout something else ??

Post by **ozy1** » Tue Jun 03, 2003 10:58 pm

When you fitted the radius arm drop down brackets, are you talking about the bolt on ones?

If so, have you found anything else with them, do they sacrifice much ground clearance? How is your upwards trvel?

Shawn

Post by **hypo** » Tue Jun 03, 2003 11:08 pm

mate of mine has these and they dont seem 2 get hung on much and and previously said it give more down travel

Post by **ozy1** » Tue Jun 03, 2003 11:12 pm

im gunna make some calls tomorrow, i would love to get this prob solved asap, as im leading a trip up to stockten with a mate who hasnt been beefore, who do you recomend, i can do the work my self, but id like prices to see if its worth me aying on the cold floor.

Shawn

Post by **Wendle** » Wed Jun 04, 2003 8:02 am

the shimmy is usually flogged out panhrd bushes, because thepanhard angle increases with any lift, it becomes less effective at stopping any sideways movement, so any movement in the bushes shows up worse. Flogged out tie-rod ends, fuct wheel bearings, bad castor settings (not enough or too much), or out of balance wheels will all add to the problem...
Here is how the castor change works with lift. 1.875deg for every inch of lift. Also shown is the amount of correction needed for a 4" lift.... :crazyeyes:

Post by **bj on roids** » Wed Jun 04, 2003 11:35 am

do not sue carlton if you fug up

YMMV and all information is intended as a guide only despite its accurate nature. :finger:

Post by **Wendle** » Wed Jun 04, 2003 11:47 am

bj on roids wrote:do not sue carlton if you fug up

YMMV and all information is intended as a guide only despite its accurate nature.

Who is this carlton that you speak of?? 8)
YMMV
WMAB
IATPCOC
H290.COM.AU :finger:

Post by **big red** » Wed Jun 04, 2003 10:18 pm

yes the brackets hit but as the radius arms are in line with them the truck seems to slide straight over the rocks in a forward direction, in a reverse direction they will get hung up though.
because the brackets fit between the cross member and the chassis it drops the cross member slightly and the front tailshaft no longer touches the cross member.
I didnt lose any up travel but gained 3 or 4 inches of down travel as the rear trailing arm pin bushes no longer bind up.
shane

Post by **ozy1** » Wed Jun 04, 2003 11:05 pm

thanks for that, i went out and bought a set, id be thiunking that your now run standard radius arm bushes, and that you also have to cut a bit out of the chassis?

am i right?

Shawn

Post by **RoldIT** » Thu Jun 05, 2003 10:13 am

Guys,

I'd be very interested to see some pics of these drop brackets once fitted. I've got a fair idea of what you are describing but as the saying goes, a picture tells a thousand words. :wink:

Cheers.

Post by **big red** » Thu Jun 05, 2003 7:33 pm

2 pics of wizard drop brackets

Post by **big red** » Thu Jun 05, 2003 7:35 pm

another one

Post by **Wendle** » Fri Jun 06, 2003 7:49 am

I have a good idea!! It will give people a direct impressoin of how the drop bracket ddodads work.
I reckon shane (drop brackets) and JK (no brackets) should both disconnect teir front shocks, reverse up some ramp type thing, and get photos of the amount of travel at the point where the arms bind, the angles of the arms, the amount of stuff/droop, and the amount of front axle steer. We could then also do the same thing with a few different types of 5-links..

Post by JK » Fri Jun 06, 2003 8:59 am

Wendle wrote:I have a good idea!! It will give people a direct impressoin of how the drop bracket ddodads work.
I reckon shane (drop brackets) and JK (no brackets) should both disconnect teir front shocks, reverse up some ramp type thing, and get photos of the amount of travel at the point where the arms bind, the angles of the arms, the amount of stuff/droop, and the amount of front axle steer. We could then also do the same thing with a few different types of 5-links..

That's so sensible it hurts...

And all that so early on a Friday morning... you must be getting excited about the long weekend or something. :finger:

I can get shots of my truck on Surfections 30deg ramp.

BTW, I don't have trouble with droop, it is my full compression that is limited by the binding.

Post by **Wendle** » Fri Jun 06, 2003 9:02 am

I just re-read what I typed up there. How's my typing going :shock:

Canberra is cold and my hands are numb.

Post by JK » Fri Jun 06, 2003 9:06 am

looks ddddddooodddddaddd ccccolddddd.

Post by **RoldIT** » Fri Jun 06, 2003 11:31 am

Thanks Big Red, I wasn't quite sure how these brackets would drop the crossmember but I can see now.

What minimum lift are these designed for? (ie 4", 6", etc)

Post by **ozy1** » Fri Jun 06, 2003 4:34 pm

well, i went out and purchased my self a set of the radius arm drop brackets and a set of second hand radius arms. Put them on last night, and the wobble in the front end is gone, i also notice my radius arm bushes where rooted, they could have been the casue of my problem the whole time, not to worry, have a good week end all.

Shawn

Post by **big red** » Fri Jun 06, 2003 6:23 pm

people have put them on 5" but the problem with a small lift is clearance.
I think they were originally designed for a 7" lifted GU but work ok on others.

Post by **big red** » Fri Jun 06, 2003 6:36 pm

heres measurements on a 30 degree ramp from a while ago.
It went up the ramp 2252mm measured at centre of hub with a 90 degree square on the ramp.
height off the ground was 1125mm.
front ways it went up the ramp 2010mm and height was 1000mm exactly.

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