SPC UCA Help

Hi all I have between 2-3" of lift from bilstein 5100 and 888 springs with SPC LR uca and not quiet sure what I should set my caster to. Right now I have it on setting "c" +3 caster. I also have 285/75/16 tires and they do rub on cab mount (I believe) when turning and hitting a bump as well. Also 1 1/4" spidertrax wheel spacers which I'd like to keep on. Any advice would be awesome thanks.

 

@nd4spdbh

 

Well


What’s your castor at ?

 

You should be around 4 on caster

 

I have it at +3 castor setting I still need to get an alignment just want it set at right setting before I do

 

Will the higher caster push my tire forward farther away from cab mount?

 

Yup

 

I seen on another post someone saying this. Not sure if what he is saying is correct though.

 

Set the ball joint to position E and all will be fine. I had 35’s on with that setting and no rubbing

 

Does that not push my tire closer to the cab mount though?

 

The plus 4 on caster pushes it forward. You can get all the way up to 6 if needed

 

No. It moves the spindle forward allowing for more LCA forward movement.

 

Nice truck! What are your settibse on your front 5100s?

 

What settings are your cams in ?

 

This is the part people forget about. In order to get max clearance in the rear of the wheel well, the lower cams MUST be maxed for caster.

 

Correct. For you to clear tires better from the cab mount, Max the LCA caster adjustment in the positive direction (front cams pulled all the way to centerline, rear cams all the way away from centerline). Doing this moves the whole hub and wheel assembly forward.

Next you can go into "negative settings" on the SPC arms (position E F and G) to gain more clearance (though not as drastic as moving the LCA forward). Also note that the higher the overall caster the much more significant the truck will pull due to road crown. Im actually down around 1.75* of caster and its so nice to not have to fight road crown.

Lastly, the beauty of the SPC arms lies within the ability to adjust camber, because with your LCA's maxed to create clearance for the larger tires, camber will be hella positive, you can tame that by sliding the upper ball joing inward to get closer to 0* camber. FYI spec is something like 1* Positive to -0.2* negative camber, Im actually around .2-.3* positive right now and steering feel is great.

 

Got an alignment done yesterday and got these numbers and now my tire clears my cabmount when flexed and drives good. That's with uca at +2 caster and cams maxed but I'd like to adjust my uppers now so I can have a bit better camber as my wheels are directonal. With me adjusting my uppers for camber just a tad will that throw my toe off though meaning I have to get another alignment??

 

id bet you are going to start to not like having to deal with such a heavy steering wheel and pulling due to road crown with those caster numbers just FYI.

As far as sliding the upper balljoint in to reduce positive camber, yes it will greatly effect Toe. Gotta remember tie rod is connected not very far away from steering axis so moving the upper balljoint in or out thus moving the mounting point in or out a bit has big changes to toe.

That stated toe is not hard to set yourself if you know what you are doing.

 

I have 3.9 on DS and 4.4 on PS for caster. I wish my steering was more heavy as I'm acclimated to solid front axle steering.
Mine also pulls to the right even though I have my caster less on the DS. (Camber 0 and toe 0) I can't figure that one out.

 

Do a smidge of toe in, and a smidge of POSITIVE camber and it should help things.

That stated, your pull to the right even though you hav ea .5* caster difference is due to road crown and high caster numbers exacerbating it. Get on a road with opposite crown (like fast lane of a divided highway) that has a noticeable slope to the left instead of the right and id bet you start pulling left hard.