Alignment Woes

[Rando]

I recently installed Bilstein 5100's on all four corners of my 2004 Tacoma TRD. In the back they are paired with Toytech AAL's to compensate for my heavy Wildernest, and in the front they are set at the middle setting ~1" to level things out a bit. After installing the front shocks, I took it in for an alignment. Previously it drove just fine, no pulling and very stable on the highway, but the front tires (which had not be rotated for 10k miles according to the previous owner) had some strange wear patterns on the front tires. The tread blocks on the edges of the tires seem to be worn down at the front edge more than the back edge fairly evenly on both sides - the tech refered to the tires as "feathered". Anyway, they rotated the worn tires to the back and set the alignment as follows:

Front Left
Camber 0.0
Caster 1.1
Toe 0.03

Front Right
Camber 0.2
Caster 1.4
Toe 0.03

Front
Cross Camber -0.2
Cross Caster -0.3
Total Toe 0.06

The only number that significantly changed between before and after was the Toe, which was previously left 0.26, right 0.19. Now the truck is very squirrely to drive on the highway. It doesn't pull in any specific direction, but it requires a lot of concentration to keep it straight and it seems to drift a lot if the road is off camber. It is actually a little scary to drive above 60.

My question is - is it the lack of toe in that causes this? What should the toe in be set at? Could it be the new shocks/slight lift? I took it back to the shop and they checked everything was tight and suggested that it may be the feathered back tires that are causing it to drift around. Any one else experienced this?

 

[Bogo]

If you want you can try adding back in slight amounts of toe in to see if it helps. What does the FSM say for your vehicle?

 

[78Bronco]

I think you need another degree or two of castor. I always thought that 3 degrees was ideal for most vehicles but maybe I'm delusional. When exiting a corner and slightly accelerate does the wheel recenter itself? It sounds like you are on the verge of death wobble and most often it's due to incorrect castor. I had a little bit of play in my idler arm and it was feathering the tires a lot, once I replaced the sloppy arm the steering was much more predictable.

 

[Rando]

I think you are rigth. After looking at the FSM, it appears that all my numbers are within spec, but at the low end. The spec is (I think):
Camber: (-0.7) - 0.9
Caster: 1.3 - 2.8
Toe: (-0.08) - 0.12

So both my toe and caster could be quite a bit higher and still be within spec. Is caster or toe more responsible for high speed stability?

I jacked up the front end and gave the front tires a shake, there was no play in the vertical direction and only a tiny amount of play in the horizontal direction, so I don't think it is ball joints etc.

I think you need another degree or two of castor. I always thought that 3 degrees was ideal for most vehicles but maybe I'm delusional. When exiting a corner and slightly accelerate does the wheel recenter itself? It sounds like you are on the verge of death wobble and most often it's due to incorrect castor. I had a little bit of play in my idler arm and it was feathering the tires a lot, once I replaced the sloppy arm the steering was much more predictable.

 

[78Bronco]

I'm assuming that you are running larger than stock size tires...

At first I was wondering what was causing my tires to feather. I did the same thing, jacked up the front end and tried to feel for play in both vertical and horizontal movement. At first I thought it was all good and the toe was causing it. Upon further evaluation as I moved the tire horizontally I could see the idler arm moving forward and aft just a little. It was only moving about 1/32" that I could tell by hand but when you are driving down the road the force is increased significantly.

I replaced the idler arm and it's now tight forward and aft. I cranked the torsion bars a little for a 1/2" of lift then had an alignment done. No more feathering and the tracking is better down the road. All I have left to do is adjust the backlash out of the steering box.

In your case I'd adjust the castor. Looking at the specs 2.1 degrees would be nominal. I'd go a little beyond that and shoot for 2.4-2.5 degrees.

 

[java]

like 78 bronco said, a little extra caster will help gain your stability back, especially with larger tires running on the high side of caster is good