Steering issues (1 Viewer)

[hotwod]

Hey guys,

Just wondering if anyone else has come across massive wandering problems when moving the tie rod from behind to in front of the axle. I've got a 3 linked 80 that drives very well on the road, but drives like a bag of sh!t after I swapped a 9.5 in with the steering up front.
It will drive straight for a bit, start to wander left so I correct a wee bit then it takes off right so I have to correct more left and so on.
The panhard/Track bar and steering link seem to be "close" as far as angles go. The only thing I changed with the steering is the tie rod placement.

 

[handcannon]

I personally have not had to deal with this, but when you changed axles you could have potentially changed the caster angle. The caster angle can affect handling.

Don

 

[hotwod]

I'll check when I get back to the truck. I made it +3° but not sure if it stayed that way with the control arm adjustments and whatnot. Wouldn't it have to be WAY out to have this much impact or steering?

 

[shawnfj40]

A couple of degrees is a lot

 

[hotwod]

Yeah? I'll check tonight.

 

[Tapage]

there would be a lot of bump steer too ..

 

[sadam_husain]

Tie rod at the front or rear of the axle makes no difference it only keeps the front wheels parallel (+/- toe in) other than that it doesn't form part of the steering geometry

 

[shawnfj40]

Tie rod at the front or rear of the axle makes no difference it only keeps the front wheels parallel (+/- toe in) other than that it doesn't form part of the steering geometry

That is why caster is the most likely culprit (assuming that all joints are tight).

 

[SuperBuickGuy]

1) alignment
2) worn TRE(s) or bushings
3) unequal length steering arms.

I think moving the steering is a red herring - because of the way its steering, a panhard bar issue would be bump steer and that's not what you're describing at all. That said, it's had to diagnose from my computer

 

[too tall]

By moving the tie rod from the rear to the front you changed your ackerman angles . If you draw a straight line from the center of the rear bumper through the center of the lower trunion , the balls of the tie rod ends are supposed to be on this imaginary line . If you didn't get new arms made or figure out a way of splaying the arms further apart from each other when going from the rear (closer together) to the front , you will not receive the benefit of proper ackerman . It will drive funny on the road .

 

[too tall]

Sorry I meant to say center of rear axle instead of rear bumper . Correct me if I am wrong if anyone knows where toyota set ackerman from different than where conventional ackerman is set from .

 

[SuperBuickGuy]

I'm curious as to why you think ackerman (aka scrub radius) has anything to do with this... not saying you're wrong, but as long as the steering arms are the same length and they are equidistant to the centerline of the car.... why would a variation in ackerman cause the issues described?

 

[too tall]

Ackerman determines the amount of toe between the two tires throughout the turning range . It changes throughout this range at a certain rate , determined via the earlier post I mentioned depending on where ackerman is set . If you change the you change the relationship between the imaginary line and the end of the steering arm , the rate at which the toe is set changes as well .

 

[rusty_tlc]

IIRC a slight toe in results in better tracking ie it's easier to maintain a straight line, to much toe in makes steering hard. No toe causes wondering. Did I get that right?
But isn't it the drag link that sets toe angle?

 

[SuperBuickGuy]

out of curiosity, are you using a variable ratio steering box? if it is and is not centered - your issue would be exactly as described.

 

[too tall]

I just looked at my wife's car (80 series) and I don't think there is enough space to put the tie rod in the front and maintain proper ackerman . It looks to me like the tie rod end would be where the rim currently is . I think toyota might have considered this when they built the 80 series . Might be the reason why they put the tie rod to the rear , to achieve proper geometry . You might be able to do it if you bent the arms and ran 20 inch wheels ? pictures might help ?

 

[SuperBuickGuy]

you're killing me with your use of the term ackerman. This is ackerman

ackerman is only about how far more or less one wheel turns in relation to the other wheel. The panhard bar doesn't affect this in any way.

which brings me back to my original question... which hole did you put the cross shaft into? the distance from the centerline of the kingpin to the TRE MUST be the same. If the panhard bar is too short (or long) compared to the steering cross shaft you will have bump steer issues.... but you won't have the issue that you described

 

[too tall]

Look at your second photo . If you take the steering arms from the rear mount tie rod and move it to the front , the tie rod end won't intersect the line generated from the center of the rear differential through the trunions ( the lower union in particular ). I was under the impression that this combined with camber built into the trunions and correct caster was the correct geometry needed for certain vehicles to track properly down the road . A larger contact patch would accentuate it as well if the geometry is incorrect . From his first post he mentioned that the only change he had made was moving the tie rod from the rear to the front . Without photos I am only speculating the only change he made was the ackerman angle .

 

[rusty_tlc]

How did the pan hard rod get into the conversation?

 

[rusty_tlc]

Look at your second photo . If you take the steering arms from the rear mount tie rod and move it to the front , the tie rod end won't intersect the line generated from the center of the rear differential through the trunions ( the lower union in particular ). I was under the impression that this combined with camber built into the trunions and correct caster was the correct geometry needed for certain vehicles to track properly down the road . A larger contact patch would accentuate it as well if the geometry is incorrect . From his first post he mentioned that the only change he had made was moving the tie rod from the rear to the front . Without photos I am only speculating the only change he made was the ackerman angle .

Actually he replaced the axle with a 9.5 if I read his post correctly.