Front suspension "tuning"

[little_joe]

On my '07 GX, I'm running Radflo 2.5" front coilovers adjusted about 2" over stock height; and I have SPC UCA's. As you all know, the SPC's have the adjustable ball joints.

My alignment specs are just about spot on, and the GX drives and handles very well. However, a couple of things have been nagging me:

1. Ball joint angle. I reached out to SPC to ask if there's a preferred, or optimum, angle for the ball joints when the vehicle is at rest. For example, should they be inline with the spindle, perfectly perpendicular to ground, or ??? They said there is no preferred or optimum angle. Doing the best I could, I set them as close as possible to the angle of the spindle. Any thoughts on this?
2. Where should the tire/wheel be in the wheelwell? I can get a picture later, but my tires/wheels seem to be a bit forward from center, e.g. toward the front of the vehicle. Only the pass side rubs the forward fender liner at full lock; and again everything else is good. Again w/ the adjustable balljoints, I wonder if the tire/wheel should be perfectly centered in the wheelwell?

Appreciate any of your thoughts on these 2 earth-shattering questions.

 

[HVLA]

Small sample size, but I have a 3 inch Dobinson's and 285/75/17s and ONLY my passenger side fender liner rubs. Driver's side doesn't.

 

[Tak555]

stock wheels?

Small sample size, but I have a 3 inch Dobinson's and 285/75/17s and ONLY my passenger side fender liner rubs. Driver's side doesn't.

 

[joabmc]

If you are going to run larger tires, then the caster will be +, pushing the wheels foreword therefore keeping them out of the body mounts.
As far as balljoint angle goes, I’m not sure I’m following you there. If your alignment is in spec, you shouldn’t be adjusting your UCAs. I have SPC UCAs, 3” lift and mine are sitting just above the tire in a level surface. They won’t be parallel to the ground though. They actually appear to look like what the OEs were without a lift. OE with a lift have a pretty severe angle.... SPC return it to a stock appearance, allow you to get back into stock alignment specs as well.

 

[HVLA]

stock wheels?

Yep.

 

[Jstawgn]

Alignment just depend on 3 basic seeing.

1. Caster
2. Camber
3. Toe

There are more stuff but normally not needed for solid rear axle.

The steps below is how I set my SPC control arm
1.OEM LCA usually moved as much as possible to the front to gain more clearance for oversize tire. Less chance needing BMC and most aftermarket front bumper give more clearance anyway Caster normally set between 3.5-4°. Can be more if you want more return to center but can give you heavier steering feel. This is achieved by adjusting the front excenttric bolt to move pivot point as far in as possible, while moving the rear excennttric bolt pivot point as far outside as possible.
2. The index tab on SPC control need to be adjusted to give that desired caster angle. The ride height will dictate the setting since that is the reason you need aftermarket UCA. The pivot point between LCA and UCA is not parallel and cause it to lose caster the taller the ride height. For my 2" lift I set it to the recommended middle +2° setting.
3. Once you set the caster you adjust caster by adjusting the upper ball joint. I put the truck at ride height and use c-clamp sideways on the ball lont to fine tune the camber.
4. Adjust the caster once more by fine tuning the excentric bolt. Passenger side usually 0.1-0.2° less to lessen the pull from the crown of the road.
5. Set toe to zero or 1/16 toe in to compensate for LCA rubber bushing flex under acceleration.

So SPC is correct that there is no preffered ball joint angle since it would be set by ride height and desired caster & camber.

I set all this just by using 2' level and toe plate at home. I am no expert by any means. I did it just because I wanted to learn.