caster correction geometry? (1 Viewer)

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was there a thread in here with a diagram showing the caster correction geometry?

stock i think is positive 2 degrees? which means the axle is canter /backward/ slightly?

them when you do a lift it goes forward by a degree an inch basically when the bushing mount in the radius arm at the back gets raised?

so somehow there is a triangle between a line through the center of the front axle to the rear bushing in the radius arm at the frame? then there is a line (the short leg of the triangle) that runs between the new bushing location with the lift to the old one without the lift?

and then a line (the hypotenuse) runs from the new bushing location (it’s longer so it’s the hypotenuse) to the line at the axle?

so because of the distances (whatever they are) between the line at the axle and the bushing at the frame - for some reason 1” at the short leg equals 1 degree caster at the axle?

then when you caster correct you adjust just the hole through the bushing at the front of the radius arm?

so the distances at the holes between the front bushings are arranged so that you need to drop the front one by some amount to get the axle to cant back by some degrees to get the caster back to 2 degrees or some positive value?

or have i got that backwards?!

i mean has anyone drawn this up? if not i’d like to but need a little help.

images are of kevin’s washer caster mod in the arizona regional forum. one of some aussie mod i don’t understand. and one of a five degree caster plate adjustment.

thanks

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I’m in the same dilemma but instead of chasing the ideal caster angle I want to correct the front diff flange angle and make it parallel to the t case flange like this


if Toyota follows this same rule, when we get the flange parallel then the caster will be where it should be. What do you guys think?

Been there, done that. The u-joints are not designed to handle that angle; tried aftermarket joints and stock Toyota. It was incredibly noisy and the driveshaft was clearly not happy. Caster was also so extreme that the truck almost felt sketchy, too.
0748A25C-2206-4FD9-9AEA-742D25015922.jpeg
 
I’m in the same dilemma but instead of chasing the ideal caster angle I want to correct the front diff flange angle and make it parallel to the t case flange like this


if Toyota follows this same rule, when we get the flange parallel then the caster will be where it should be. What do you guys think?
just to be clear for the sake of being clear. i just want to understand the issue geometrically. i mean i do need to correct for 3” if lift as a practical matter.
but part of buying this rig for me is wrenching in it and wrenching means i learn. and i like learning the “theory” too. so this is right in line with that.
 
Let me google that for you:


These look like pretty good reading on the subject. The last one is all the google hits. :cheers:
 
You mean you might actually have to read some of the results when you google? I prefer to get some general information on the subject and then, if necessary, ask someone very specific questions that might not be in the generic information. Understanding caster geometry certainly isn't a specific land cruiser subject. And if it's described to you in a very prescriptive way using the land cruiser as the model, have you really learned all you can? But to each their own. Carry on.

Edit: That sounds overly critical; don't really mean any offense but you said you wanted to "learn about Caster geometry".
 
Been there, done that. The u-joints are not designed to handle that angle; tried aftermarket joints and stock Toyota. It was incredibly noisy and the driveshaft was clearly not happy. Caster was also so extreme that the truck almost felt sketchy, too.
View attachment 2455193
What caster numbers did you have with this set up?

ive run as high as 7 deg On rigs without issue. I have a 2” lift. But use the Slee 5 deg correction plate. Mine drives great with stock shafts.
 
was there a thread in here with a diagram showing the caster correction geometry?
IIRC, Rick had done a mechanical drawing of it. Search "caster" by landtank.

 
IIRC, Rick had done a mechanical drawing of it. Search "caster" by landtank.

thanks a /lot/ jon. i will read that one. here are the three that @medtro linked for me in the other thread (link above). i will try to post them here when i get a minute.

B874EE1D-F53A-4405-A14B-01B6ED4F14B3.jpeg
 
For reference these were my numbers after a 3”, closer to 4” lift with Delta VS radius arms.

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EDIT: the attached image was my numbers before the Delta VS arms. I posted the wrong image. This was in no way an attempt to discredit Delta.

Attached is the correct specs after installing the Delta 4” arms.

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thanks man.
so does anyone have the lengths between the three bushings? meaning leg A and leg B?
also. can anyone help me with the geometry shown here? the two dots are the center of the two bushings which is the connection at the axle.
positive 3 degrees caster is a perpendicular from the line between the two connections at the axle? and positive caster is canted back? so the longer line here is a plumb line and the shorter line is the perpendicular?
green line is just a horizontal at the connection to the radius arm at the frame? but it has nothing really to do with the caster angle at the axle i think.
also, according to the diagram the axle itself is getting rotated but also pulled back toward the back of the truck? and this happens sort of more per inch the more you lift it? meaning an inch or two lift pulls it back a little but the more you lift the more it gets pushed backward (and not linearly)?

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thanks man.
so does anyone have the lengths between the three bushings? meaning leg A and leg B?
also. can anyone help me with the geometry shown here? the two dots are the center of the two bushings which is the connection at the axle.
positive 3 degrees caster is a perpendicular from the line between the two connections at the axle? and positive caster is canted back? so the longer line here is a plumb line and the shorter line is the perpendicular?
green line is just a horizontal at the connection to the radius arm at the frame? but it has nothing really to do with the caster angle at the axle i think.
also, according to the diagram the axle itself is getting rotated but also pulled back toward the bs k of the truck? and this happens sort of more per inch the more you lift it? meaning dn inch or two lift pulls it back a little but the more you lift the more it gets hacked bs ward (and not linearly)?

View attachment 2455422
I used to know the dimensions of the radius arms, back when I drew up some and made a couple for a friend but that was five years ago so I‘ve slept, eaten, etc since then. At any rate, unless you’re building arms, those numbers are irrelevant.

The green line is the same as a level shop floor/frame line, giving you a reference point.

The axle moves back the further you lift. So the wheelbase changes at ride height, but is irrelevant because on compression the arc it swings in puts it in a happy place to stuff the tire. This is why I prefer the washer mod or Joey’s caster plates over others. When you pivot the axle on that rear axle mount bolt, the axle tips backwards, shoving it into the wheel well on compression.
 
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For reference these were my numbers after a 3”, closer to 4” lift with Delta VS radius arms.

View attachment 2455309
that is the most confusing way to display that info I've ever seen! also, don't see any numbers that are close to correct for a caster reading. Which arms did you get?
 
that is the most confusing way to display that info I've ever seen! also, don't see any numbers that are close to correct for a caster reading. Which arms did you get?

I bought the 4” lift versions. It feels leaps and bounds better over the stock arms with bushings but I think I might look to see if someone would like to trade for some 6” versions.
 
I bought the 4” lift versions. It feels leaps and bounds better over the stock arms with bushings but I think I might look to see if someone would like to trade for some 6” versions.
Can you send me any other info you have from the alignment shop? Something that says “caster is xxx” or something? What was your order number? Can you send me an email info @deltavs.com with all this info?
 
Can you send me any other info you have from the alignment shop? Something that says “caster is xxx” or something? What was your order number? Can you send me an email info @deltavs.com with all this info?

Sure thing. We emailed a bit back and forth before I pulled the trigger on the 4” versions.
 
I used to know the dimensions of the radius arms, back when I drew up some and made a couple for a friend but that was five years ago so I‘ve slept, eaten, etc since then. At any rate, unless you’re building arms, those numbers are irrelevant.

The green line is the same as a level shop floor/frame line, giving you a reference point.

The axle moves back the further you lift. So the wheelbase changes at ride height, but is irrelevant because on compression the arc it swings in puts it in a happy place to stuff the tire. This is why I prefer the washer mod or Joey’s caster plates over others. When you pivot the axle on that rear axle mount bolt, the axle tips backwards, shoving it into the wheel well on compression.
looks like another thread on here is showing christo saying center of rear hole on the radius arm to center between the two in the front (presumably the axle or close to it) is right about 33”. FWIW.
 
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