Caster Angle

[bwillie]

I am in the process of putting together/measuring, etc. the new front links. I want to get the stearing back the way it was before the lift. Can someone tell me what the proper caster angle was when it left he factory?

[4x4rancher]

IMO the castor angle would remain unchanged if all you did was put in taller springs.

[Karl Ingolfsson]

Somone posted here that caster angle is only +1,5°.

This is in hand vith slow return of steering wheel and sensitivity to suspension lift.

There are 4 ways to corect caster angle after mounting longer coils:

1
Lover the mounting points of the radius arms where it connects to frame. This also corrects the tilt of the radius arms and gives good direction of diff flange relative to TC. This mod is allways done in professional suspension lifts here.

2
Build new arm mounts on the housings.

3
Cut the housings outside the arm mounts and weld it back with right caster angle.

4
New radius arms that give right caster for a different coil lengt

Bending the radius arm is bad medicine.
Off centered bushings at radius arm/housing connection wil not last long and most likely not flex well and therefor limit winding of housing.

It is practiced here to lower the arm mounts slightly more than the suspension lift to increase caster slightly when used with 35" to 44" high tires and rim width 10" to 17".
If you are using wide rims with little backspace and relatively small tires (35" and smaller) It can be recomended to use a little more caster than stock.

I use 9,5" rims with original backspace and 35" tires and it drives well with this settup.

But I personally like more caster and increased return to center tendency.

[bwillie]

THANKS!!! That is what I was looking for. I am rebuilding the front completley- coil overs, links the whole shabang. I will be able to change the caster with the new 3 link set up.

I am running 37x13.5 tires- is there a degree that you typically aim for other than stock?

[Karl Ingolfsson]

37 x 13,5 is a moderate tire.
I would mount it on 11" wide rim with as much backspace as possible and not change suspension at all. Instead I would cut away fenders and inner fenders and trim/rebuild the bodymounts behind the front wheels.
If you mount longer coils, just lower the radius arms equally or slightly more to get increased "straight" tendency.
Tires will rub front radius arms and anti sway bar at full turn but neither body or suspension lifts changes that.

[Brent]

The lift will change the caster. Then I would think that 1.5* is not nearly enough for a stock setting. I think you need to get it around 5-6* to get the self centering and directional stability Karl talks about. I would be most tempted to use the stock arms as they are very strong steel forgings and drop the mounting point on the frame the amount of the lift, as mentioned.

[4x4rancher]

Help me understand this,
Where is the datum from which you measure this angle?

[Karl Ingolfsson]

4x4rancher - 6/29/2005 12:37 AM

Help me understand this,
Where is the datum from which you measure this angle?

Search the forum for "caster" and/or "lift" an you come across something....

[Brent]

You can think of it like a kingpin inclination. Draw a vertical line through the center of the wheel. The actual steering axis is not along that line but tilted back at the top. I was probably a little off on the measurement on the G. I suspect that it could in fact be as little as 1.5*. I just recalled running much more on another car.

Now, when you lift the G and do not move the trailing arms, the axle rotates forward at the top (of the diff) eating away at that caster angle. Dropping the arms in back would rotate the axle back at the top increasing caster again.

I think I got it[;)] Hope that helps!

[Dai]

Caster on a 460 is 5 degrees +/- 20'
Toe-in 0 +/- 1mm
Camber 1 degree +/- 20'
Kingpin inclination 9 degrees +/- 20'

This Data is from the Factory Owners Manual.

With the springs I used the lift wiped out my caster. Lilac ones stripe rears/White 2 stripe fronts. On a short wheelbase truck. It self centers but is directionally exciting to drive.

-Dai