Alignment/Measurement Question - Caster of Front Wheels

If the tire's contact patch is BEHIND the point where the "kingpin
axis" would be projected onto the pavement, is this positive or
negative caster?

Since I (luckily) have one side where the caster/camber is presumably
correct, can I fine-tune the match using driving characteristics? In
other words, if the vehicle pulls/drifts to the driver's side, which
side needs positive caster reduced (assuming equal camber and level
pavement)?

Thanks,

Martin

Martin wrote:
> I recently replaced upper ball joints on a '96 Dodge 3500 (1-ton) van.
> This vehicle uses pressed-in ball joints, and I replaced them with a
> standard C-frame tool. After a few months, one of the ball joints
> backed itself out (this is a poor design, IMO). I pressed it back in,
> and tack-welded it in a few spots. So far, it's holding just fine.
>
> In order to do the weld, I removed the upper A-frame. Of course, I
> didn't think to mark it's position (uses no shims, just slotted bolt
> holes to adjust caster/camber) until I'd already loosened the bolts and
> let things shift.
>
> I'd like to get the truck properly in alignment. If that's not
> possible, at least driveably close until I buy new tires and have a
> shop fine-tune it.
>
> I think I can measure camber with a plumb bob, and toe-in's a
> no-brainer, but how in the devil can I measure caster?
>
> Also, is there an online reference where I can find the alignment specs
> for my vehicle?
>
> best regards,
>
> Martin