Setting Toe-in, question? Bumpsteer problem.

[Psycho71]

Got the front end all rebuilt last weekend. I eyeballed the toe on it and was way off. I had it toe'd out, about 3/8",the thing walked all over the road and would follow the least little depression. Was a chore just to get it back home after a run down the street.

So today I got a bit more scientific about it. I picked up two 4' long straight edges from Home Depot, and bolted an "L" bracket to them so they'd bolt to a wheel stud. Took off the wheels, and bolted them up. Worked out really well, after I set them with a level so the measurements would be consistent.

So, I measured out from the centerline of the hub 17.5" (the radius of my 35" tires) and set the toe in at 1/8". I helped tremendously! But still didn't completely fix the problem.

How much toe-in is acceptable? I'm thinking of setting it at about a 1/4" and see if it gets any better. Don't want ti chewing tires up, but can't drive it while it tries to drive itself.

Also, the Burb has a slight lift, and the link from the pitman arm to the steering arm on the hub, has a slight angle to it. I know that it should be level or close to it. Just wondering if this is contributing to the bumpsteer I am experiencing. I'm not against a raised steering arm, but honestly, mine ain't that far out of whack. Not far enough for me to see how it could be an issue, but I've been wrong 2-3 times before So should it be completely level? Or is a slight amount of angle tolerable?

Oh yeah, no slack in the steering box or shaft, so the problem must be in the geometry somewhere.

Thanks for any advice.

'85 K20 burb. Unknown lift up front, 4"shackle flip on rear (sits about level now). 36x12.5x16.5 hummer take-offs on 9.75" wide wheels.

[Transformula]

For a solid axle, 1/16 inch toe in is a good setting. As the rolling resistance increases from driving down the road, toe will be 1/32" to 0", which is what you want. Even a slight bit of toe out would not cause too much wandering by itself. How about caster? Is there enough positive caster? (Top of spindle/ ball joints leaning rearward). 3-8 degrees is good. Provides for straight-line stability and steering wheel returning to center.
As far as the drag link, the leveler, the better. If it's at an angle, there will always be some bump-steer in one direction.

[Psycho71]

Thanks for the info. I will check the caster this weekend. Given your response, I suspect it might be a source of my problems as well since I raised the rear of the truck about 4", effectively removing caster. I did notice that since raising the rear of the burb, the front tires don't lean as much as they did before when i lock the steering. The front was already lifted when i got the burb, I suspect. So all I did was raise the rear to match the front. Not sure what all had been done since I bought the burb from a fella who bought it and never did anything with it. So getting mod info was impossible.

So, since it's a solid axle which indexes on the spring perches, are angled shims the only/easiest way to correct caster? I know cutting the perches off and re-welding them on at the correct position would probably be best, but not sure if I want to put that much effort into the 10 bolt at this time, since a D60 upgrade will likely be in coming in the future.

Am I missing something? Or is this my best bet for a caster angle correction? Also, what implications will any changes have on my front pinion angle? Am I going to create another issue when i start messing with the angles to get my caster correct?

[Transformula]

THere's no problem with caster shims at all. Especially since you're testing things out right now, you don't want to be cutting and welding just yet. Test out some angles with shims and if that fixes it, either leave it alone, or then you could cut and re-weld the perches. (Just make sure the spring centering pin goes all the way through and into the perch hole). You might have to find a happy "Acceptable" medium between enough caster and pinion angle. I think mine is about 4.5 degrees positive caster and something like 5-6 degrees at the front u-joint. But 4 wheel drive isn't used all the time so it's alright for me!