building extended radius arms. Caster question

[guido51]

New to the site here, but not new to early 4x4 explorers and rangers.
I'm piecing together a lift for my 1992 explorer sport.

My plan is to build this thing as cheaply as possible. I plan to do a cut and turn and build radius arms by extending the stock ones. I've collected parts throughout the year on 50% off days at the boneyard (coils, stx brackets, drop pitman arm, manual 1354 tcase and 8.8 rear with disc brakes) and am about ready to Start on this project.

I have a decent amount of fabrication experience and understand how the ttb works.

My question is about how much caster do I need for a 4" lift?
From what I read, if using 0* bushings and the beam square with the floor at ride height,
there should be around 5* of caster already in the beam. Is this correct?
Is this enough caster for 4" of lift? Or do I add a little more into the radius arm, let's say 2*. That would give me a total of 7* at ride height?

Am I way off on this? I know it's inevitable, but I'm trying to lessen the trial and error factor of building it yourself.

 

[plcrew]

Great post, Im right in the middle of building extended radius arms myself. Mines a little different to start, going with minimal lift or no lift at all. Just trying to see what I can get with the stock pivot brackets, and go from there. mostly will be driven on the road (95% of the time), and as little money as possible spent. going with stock caster for my set up.

 

[Maniak]

I don't know if you saw my thread when I modified a set of extended stock radius arms...

http://www.explorerforum.com/forums/showthread.php?t=246044

In short. with the extension done like it was AND around 4" of lift I has 12 degrees of caster.. Since then I've increased the lift to around 6" and now the caster is better...

I'm also using cut/turned beams (from BTF - Brandon and Travis Fab in Ca) which is using the move the ball joint method.. I used stock Explorer axle pivot brackets although I did add some metal to the one on the driver side so it could grab the frame in another location for some added strength..

~Mark

 

[plcrew]

Why do we need to add caster when we lift an explorer or any TTB front end vehicle? Ive read the same thing on gofastbronco.com lots of caster is added to the TTB front end when lifting.

 

[Maniak]

Because the word "caster" can mean + or - caster..

By lifting (and not adding any back in) you are taking away caster.. If you take too much away you end up with the broken shopping cart wheel affect where it shakes all over..

Positive caster will try to keep the wheels straight but it messes up the turning (tire lean) when you go too far that way...

I believe the Factory spec for the 1st gen ranges from +2 to +6 degrees caster

As a side bonus.. the vehicle will pull towards the side that last the least amount of positive caster...

~Mark

 

[guido51]

Thanks for the link and info Mark! I'm guessing I'm gonna have to play around with the radius arm setup since I'm not too sure how much lift I'm gonna have with the brackets and springs I have. Looks to be around 4".
With the truck level and at ride height, if I put an angle finder on the flat front of the ttb housing by the knuckles, is that where i can find an acurate caster setting? Is around 6* of caster a good set point?

 

[Maniak]

That's how I do it...

I also have an SPC 91000 alignment tool but I've never used it to measure caster.. It's possible but it's more involved than just testing camber and the face of the beam seems to work just fine for me..

~Mark

edit: I almost forgot. measuring it at the face of the beam is measuring the beam, not the ball joints.. if you have cams on the ball joints with adjustment for caster measuring "on the beam" wont' take that into account.

 

[guido51]

Ok. Thanks for clearing this up for me! I have a better understanding on this now. Got the truck apart. Now to make some progress hopefully....